BSMS#1485550, VOL 0, ISS 0

A review on high stiffness aluminum-based composites and bimetallics

Sajjad Amirkhanlou, and Shouxun Ji

QUERY SHEET

This page lists questions we have about your paper. The numbers displayed at left can be found in the text of the paper for reference. In addition, please review your paper as a whole for correctness.

Q1. A disclosure statement reporting no conflict of interest has been inserted. Please correct if this is inaccurate. Q2. Please provide volume number and page range for the reference "4". Q3. Please provide publisher location for the references "15, 16, 65, 84, 85". Q4. Please expand all author names for all references instead of using "et al.". Q5. Please provide publisher details for the reference "64".

TABLE OF CONTENTS LISTING

The table of contents for the journal will list your paper exactly as it appears below:

A review on high stiffness aluminum-based composites and bimetallics Sajjad Amirkhanlou, and Shouxun Ji CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES https://doi.org/10.1080/10408436.2018.1485550

1 53 2 54 3 A review on high stiffness aluminum-based composites and bimetallics 55 4 56 5 Sajjad Amirkhanlou and Shouxun Ji 57 6 Brunel Centre for Advanced Solidification Technology (BCAST), Institute of Materials and Manufacturing, Brunel University London, 58 7 Uxbridge, United Kingdom 59 8 60 9 61 ABSTRACT KEYWORDS 10 The Young’s modulus of aluminum-based materials is one of the most important mechan- Cast aluminum alloys; 62 11 ical properties in controlling structural performance. The improvement of the Young’s stiffness; high modulus 63 modulus of castable aluminum-based materials is essential for improving their competive- materials; bimetallic 12 materials; metal matrix 64 ness in light weighting structural applications. Currently, there are limited options for cast 13 composites; light metals 65 aluminum alloys with outstanding Young’s modulus. Also, for further stiffness improvement 14 and thereby weight lightening, in-depth understanding of the relevant mechanisms for 66 15 modulus improvement in aluminum alloys is necessary. This review focuses on the Young’s 67 16 modulus of cast aluminum-based composites, as well as aluminum alloys reinforced with 68 continuous metallic fibers (bimetallic materials). The effect of different chemical elements in 17 cast alloys, the constituents of in-situ and ex-situ formed aluminum matrix composites, and 69 18 the wire-enhanced bimetallic materials on the Young’s modulus of aluminum-based materi- 70 19 als are reviewed. The Young’s modulus of cast aluminum alloys can be improved by: (a) 71 introducing high modulus reinforcement phases – such as TiB2,SiC,B4C, and Al2O3 – into 20 aluminum by in-situ reactions or by ex-situ additions; and (b) forming bimetallic materials 72 21 with metallic wire/bar reinforcement in the aluminum matrix. The performance of a stiff alu- 73 22 minum depends on the volume fraction, size, and distribution of the high modulus 74 23 phases as well as the interface between reinforcement and Al matrix. One of the major con- 75 cerns is the reduction of the of castings after adding specific high modulus phases 24 to increase the Young’s modulus. Further research into the improvement of Young’s modu- 76 25 lus and the ductility of aluminum alloys is necessary through proper selection of reinforce- 77 26 ment, optimizing interface, and distribution of reinforcement. 78 27 79 28 80 29 Table of contents 81 30 82 1. Introduction ...... 2 31 83 2. Stiffness improvement in bimetallic materials ...... 2 32 84 2.1. Al/ Bimetallic Materials ...... 3 33 85 2.2. Al/Stainless Bimetallic Materials ...... 5 34 86 2.3. Al/ Bimetallic Materials ...... 6 35 87 2.4. Other Bimetallic Materials...... 7 36 88 3. Stiffness improvement in aluminum-based composites ...... 7 37 89 3.1. Al/TiB Composites ...... 9 38 2 90 3.2. Al/TiC composites ...... 10 39 91 3.3. Al/SiC Composites ...... 11 40 92 3.4. Al/AlN Composites ...... 11 41 93 3.5. Al/ZrB -Al Zr Composites ...... 13 42 2 3 94 3.6. Other Particulate-reinforced AMCs ...... 13 43 95 3.7. AMCs with Continuous Reinforcement ...... 14 44 96 4. Summary and future outlook ...... 15 45 97 Disclosure statement ...... 16 46 98 Funding ...... 16 47 99 References ...... 16 48 100 49 101 50 CONTACT Shouxun Ji [email protected] 102 51 Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/bsms. 103 ß 2018 Taylor &Francis Group, LLC 52 104 2 S. AMIRKHANLOU AND S. JI

105 1. Introduction matrix to form aluminum matrix composites (AMCs) 158 106 has been the topic of numerous investigations,18,19 in 159 Weight reduction through applying aluminum struc- 107 which the high modulus phases can be generated by 160 tural components in aerospace and automobile indus- 108 in-situ reactions with different metallic elements or 161 tries is one of the most promising ways to decrease 109 nonmetallic ceramic compounds, or by direct injec- 162 energy and fuel consumption.1,2 These structural com- 110 tion of foreign phases.20,21 In a similar way, bimetallic 163 ponents, in particular shaped castings, are usually 111 materials such as wire-reinforced metallic structures 164 112 designed on the criteria of either strength or 165 3,4 can be recognized as a special category of composites 113 stiffness. When the yield strength is used as the 22 166 design criterion, aluminum alloys with much higher in macroscale, which can be used for an effective 114 ’ ’ 167 strength than pure aluminum are commercially avail- increase of Young s modulus. In general, the Young s 115 modulus of cast aluminum alloys is less sensitive to 168 116 able and these can be selected for industrial applica- 169 5,6 alloying as compared to the stiffer reinforcement in 117 tions. However, when the stiffness is used as the 170 AMCs or bimetallic materials. 118 design criterion, there are limited options for the alu- 171 The understanding of the successes and challenges 119 minum alloys with significantly increased stiffness 172 7,8 in the stiffness of materials can serve as a guidepost 120 than that of aluminum. There is a lack of thorough 173 for where future work is needed in order to effectively 121 understanding of the stiffness of aluminum alloys and 174 propel the technology development. Therefore, this 122 aluminum-based materials that can be used to make 175 review focuses on the Young’s modulus of cast alumi- 123 castings. Moreover, some of the strengthening mecha- 176 num alloys, composites, and bimetallic materials and 124 nisms, which result in a significant improvement in 177 their fabrication processes, aiming to provide a snap- 125 yield strength, have no obvious effect on the stiff- 178 9,10 shot of the current progress on cast aluminum alloys 126 ness. This has limited the applications of alumi- 179 for improving their Young’s modulus. The paper is 127 num alloys in the shaped castings and components 180 128 that require high modulus to achieve further weight outlined as follows. Section two summarizes the effect 181 ’ 129 reduction in the aluminum structures. of wire reinforcement on the Young s modulus of alu- 182 130 As the intrinsic property of materials, the Young’s minum-based bimetallic materials. The properties of 183 131 modulus of cast aluminum alloys can only be margin- commonly used reinforcements are discussed in asso- 184 132 ally influenced by manipulating traditional metallur- ciation with the merits and limitations of processing. 185 133 gical variables that can change the microstructure of Section three focuses on the stiffness improvement by 186 11,12 134 aluminum alloys significantly. Minor changes of in-situ and ex-situ composites. A discussion on the 187 ’ 135 microstructure by alloying elements as well as deform- processing, microstructure, and Young s modulus of 188 – 136 ation and heat treatment processes cannot improve the in-situ and ex-situ reinforcement including TiB2, 189 13 – 137 the stiffness of Al-based materials. Lucena et al. TiC, AlN, ZrB2, and Al2O3 in cast Al alloys is pro- 190 138 studied the variation in the Young’s modulus of vided. Section five ends the paper with the summary 191 139 AA1050 (>99.5% Al) with cold plastic deformation and future outlook. 192 140 (tension test). Young’s modulus decreased from 193 141 69 GPa (initial material) to 63 GPa (2.5% strain), then 2. Stiffness improvement in 194 142 increased to 65% (6% strain) and finally stabilized to bimetallic materials 195 143 66 GPa (13% strain). Villuendas et al.14 showed that 196 144 the Young’s modulus of AA2024 and AA7075 in solu- Bimetallic materials can be considered as a special 197 145 tion treated, deformed, and aged alloys were slightly type of composites, in which continuous metallic 198 146 lower (<2% reduction) than those of the undeformed wires/bars are used as skeletons or frames for over- 199 23,24 147 specimens. Despite of deformation and heat treatment, casting with conventional casting methods. 200 148 chemical composition and phase constituents are two Overcasting is casting process when liquid molten 201 25 149 main factors governing the stiffness properties of cast- metal is poured onto a solid-state metal/ceramic. 202 150 ing alloys.15 Processes that can change the microstruc- The network structures, or skeletons or continuous 203 151 ture significantly can alter the Young’s modulus. The fibers, have been extensively used in polymer/ceramic 204 152 high concentration of alloying elements can have per- matrix composites,26,27 but the bimetallic materials are 205 153 ceptible influence through the contribution in bind particularly used in this review for the metal–metal 206 154 interaction. In fact, the high modulus phases can be mixture made by casting, in which the metallic skele- 207 155 introduced into the aluminum matrix through major tons or frames made by high modulus reinforcement 208 156 addition of alloying elements and/or ceramic par- are covered partially or completely by aluminum 209 157 ticles.16,17 The addition of ceramics into the aluminum alloys. The skeleton preforms not only provide a 210 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 3

211 264 212 265 213 266 214 267 215 268 216 269 217 270 218 271 219 272 220 273 221 274 222 275 223 276 ’ 34 224 Figure 1. (a) Tensile curves and (b) Young s modulus of pure Al and Al/Ni bimetallic materials. 277 225 278 for making network structure in the existing literature. 226 279 Limited studies for other potential metals have 227 280 been performed. 228 281 229 282 230 2.1. Al/Nickel Bimetallic Materials 283 231 284 The interconnected network made by continuous 232 285 wires of Inconel 601 (12 mm diameter) has been used 233 286 to reinforce aluminum alloys through sintering the 234 287 wires before infiltrating aluminum melt by squeeze 235 288 casting.32,33 Figure 1(a) shows the stress–strain curves 236 35 289 237 for pure Al and Al/Ni bimetallic materials. The 290 238 remarkable improvement of ductility is attributed to 291 239 the absence of defects in the microstructure of the Al/ 292 240 Figure 2. Young’s modulus of as-cast and deformed Al/Ni Ni bimetallic materials. Figure 1(b) shows the vari- 293 37 ’ 241 bimetallic materials. ation of the Young s modulus of Al/Ni bimetallic 294 242 materials as a function of the volume fraction of the 295 243 controlled and stable reinforcement, but also offer reinforced wires, in which the upper and lower curves 296 ’ 244 new architectures and increase the Young s modulus correspond to the ROM and IROM models computed 297 28 ¼ ¼ ’ 245 and provide more effective load transfer. using EAl 70 GPa and EIn601 206 GPa. The Young s 298 246 Compared with the reinforcements such as par- modulus increases in the bimetallic materials with 299 29 30 247 ticles, whiskers, short fibers, and continuous increasing the Ni volume fraction. Most of the results 300 31 248 fibers used in AMCs, the metallic network structures are close to the average between the two bounds 301 249 or skeletons are likely desirable to perform more effi- defined by the ROM and IROM models. The Young’s 302 250 ciently, especially in reinforcing the local area of a modulus can reach a level of 95 GPa, while the elong- 303 251 cast component with relatively low cost and more ation is still more than 7% in the Al/30 vol.% Ni 304 36 252 flexible in manufacturing through casting processes. wire-reinforced bimetallic materials. The deform- 305 253 AMCs usually present low fracture toughness due to ation has no significant effect on the Young’s modulus 306 254 the brittle nature of reinforcement, which restricts of the Al/Ni bimetallic materials, as shown in 307 255 their applications. The network structure fabricated by Figure 2. The Young’s modulus under as-cast condi- 308 256 metallic wires can be 1D, 2D, or 3D interconnected tion is very similar to that under as-deformed condi- 309 257 structures with appropriate surface treatment, which tion,34 which is due to the fact that heat treatment 310 258 enhance the interface bonding during casting process and metal forming do not change the volume fraction 311 259 and improve the modulus without scarifying ductility of high modulus phases in the aluminum alloys and 312 260 and toughness. The network structure and the inter- thereby negligible change has been reported after 313 261 face are two critical aspects for the manufacturing of these processes.14 314 262 sound bimetallic materials. According to the nature of The interface between Al matrix and wire 315 263 metals, nickel and steel/iron are two popular options reinforcement plays a critical role in stiffness 316 4 S. AMIRKHANLOU AND S. JI

317 370 318 371 319 372 320 373 321 374 322 375 323 376 324 377 325 378 326 379 327 380 328 381 329 382 330 383 331 384 332 385 333 386 334 387 335 388 336 389 40 337 Figure 3. Mechanism of nucleation and growth of the nodules in the Al/Ni bimetallic materials. 390 338 391 enhancement in the bimetallic materials. Salmon 339 38 392 340 et al. investigated the influence of the oxidation of 393 341 Ni wire on the mechanical properties of Al/Ni bimet- 394 342 allic materials and found that an optimum stress and 395 343 ductility can be obtained with an appropriate oxida- 396 344 tion of the Ni alloy during sintering. The mechanical 397 345 properties can be justified as a result of compromise 398 346 between the sufficient oxide roughness to the desired 399 347 wire/matrix adhesion and the limited oxidation to 400 348 prevent an excessive degradation of the wires. The 401 349 tensile properties of Al/Ni bimetallic materials are 402 350 sensitively affected by the nature of the layer of oxide 403 351 barrier which protects the wires from the reaction 404 39 352 with the matrix during casting. The ductility of Al/ 405 353 Ni bimetallic materials can be improved by tuning the 406 ’ 354 conditions during the sintering process and Figure 4. Young s modulus of Al-13 wt.% Si alloy reinforced 407 with Ni wires.41 355 introducing a barrier layer into the Al/Ni interface. It 408 356 has been found that the partial conversion of the bar- 409 þ 357 rier layer into a mixture of Al2O3 Cr2O3 oxides Young’s modulus can be significantly increased with 410 358 forms the precipitation of a layer of NiAl3 grains on the increment of Ni contents in the Al-13 wt.% Si alloy. 411 359 top of the oxide layer, as shown in Figure 3.41 When Comparing the results shown in Figures 1–4,the 412 360 the reduction process of Ni and Fe oxides by Al is reinforcement is more effective in the alloys than that 413 361 completed, Al can diffuse across the oxide layer to in the pure aluminum. 414 362 form aluminide nodules by reacting with the constitu- Two parameters are important in the processing of 415 363 ents of the Ni wire. The formation of these nodules bimetallic materials. One is the initiation of a reaction 416 364 can increase the flow strength and the ductility in Al/ between the wires and the matrix, which is normally 417 365 Ni bimetallic materials.40,41 controlled by the cooling rate during casting, and the 418 366 The matrix materials also affect the Young’smodu- second is the stability of the oxide barrier 419 367 lus of the bimetallic materials. Boland et al.41 investi- at the surface of the wires. The stability of the oxide 420 368 gated the stiffness of cast Al-13 wt.% Si alloy reinforced barrier can be increased either by a pre-oxidizing 421 369 by Inconel 601 wires. As shown in Figure 4,the treatment for the reinforcement wires or by specified 422 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 5

423 476 424 477 425 478 426 479 427 480 428 481 429 482 430 483 431 484 432 485 433 486 41 434 Figure 5. Optical micrograph of (a) Al/20 vol.% Ni, (b) Al/80 vol.% Ni, and (c) Al-13Si/20 vol.% Ni bimetallic materials. 487 435 488 436 489 437 490 438 491 439 492 440 493 441 494 442 495 443 496 444 497 445 498 446 499 447 500 448 501 449 502 450 Figure 6. (a) Stress–strain curves for the bimetallic materials with different volume fraction of steel wires and (b) the correspond- 503 451 ing Young’s modulus.40 504 452 505 453 alloying elements to decrease the melting temperature 2.2. Al/Stainless steel Bimetallic Materials 506 454 of the matrix. The Cr-rich passivation layer on the sur- 507 Fabrication of aluminum-based bimetallic materials 455 face of IN601 can increase the refractoriness in oxidiz- 508 reinforced by 3D entangled stainless steel wires has 456 ing environments. This will reduce the reactivity of the 509 been successful using mono-filament annealed 304 457 wires toward Al during overcasting. On the other 510 stainless steel wires with 100 mm in diameter in a pre- 458 hand, when the matrix is Al-Si alloys, the Si platelets 511 form structure.34,36 The continuous wire was firstly 459 tend to nucleate preferentially at the wire/matrix inter- 512 coiled around a ø1.5 mm rod to form spring-like seg- 460 face. This phenomenon has been reported to occur 513 ments, which were subsequently stretched and 461 commonly in the composites with SiC, Al2O3,orTiB2 514 462 reinforcements with the particle pushing mechanism.40 entangled to form a pre-compacted sample for 515 – 463 Therefore, the presence of Si in Al induces a strong squeeze casting. The nominal compressive stress - 516 464 reduction of the reactivity between the wires and the strain curves are shown in Figure 6. The yield 517 ’ 465 matrix, which can result in the further improvement in strength and the Young s modulus of the bimetallic 518 466 the Young’s modulus of the bimetallic materials. As material increase as the volume fraction of the steel 519 467 illustrated in Figure 5,noreactioncompoundinthe wires increases. The yield strength can reach 318 MPa 520 468 matrix could be detected in the bimetallic materials for the bimetallic material reinforced with the 35.4 521 469 processed using optimized pre-oxidized preforms.15 It vol.% of entangled stainless steel preform. The 522 470 is necessary to note that the interface requirement is Young’s modulus of Al/26 vol.% stainless steel bimet- 523 471 different between the AMCs and the bimetallic materi- allic material is 124 GPa, which shows a significant 524 472 als. In AMCs, the interface is preferred to be clean improvement in comparison with that of the 525 473 without any reaction. However, a limited reaction layer A356 alloy. 526 474 is preferred in the bimetallic materials for the better The microstructures of A356 matrix alloy rein- 527 475 mechanical properties. forced by 3D entangled wires are shown in Figure 7. 528 6 S. AMIRKHANLOU AND S. JI

529 The wire segments show different morphologies in the obvious that the Young’s modulus increases with 582 530 matrix with homogeneous distribution. When the pro- increasing steel volume fraction. When the intercon- 583 531 cess is properly controlled, the introduction of wires nected structures are used to improve the Young’s 584 532 has little influence on the microstructures of the modulus, the selection of the desirable volume frac- 585 533 matrix. In optimum conditions, the cohesion between tion of the reinforcement and the structural design 586 534 the matrix and the wires is well obtained and no obvi- should be considered as important criteria. 587 535 ous traces of interface reaction can be observed 588 536 589 because of the prevention of the reaction by the oxide 2.3. Al/Iron Bimetallic Materials 537 barrier layer on the metallic wire,42 which offers the 590 538 591 best improvement of the Young’s modulus. Interconnected wires in the form of three-dimensional 539 592 The network structure of stainless steel can also be preforms are an approach to improve the Young’s 540 593 fabricated by sintering the wires before infiltrating the modulus by continuous steel/iron reinforcement in Al 541 37,40 594 aluminum alloys through casting. The improvement alloys. Gupta et al. fabricated several types of 3D 542 595 of the Young’s modulus without significantly scarify- preforms using the galvanized AISI 1008 wire of 543 596 ing the ductility is achievable in bimetallic materials 0.8 mm diameter coated by 10.8 vol.% . The geo- 544 597 reinforced by an interconnected network of continu- metries of the two types of reinforcement preforms 545 598 ous wires of stainless steel.41 Figure 8 shows the are shown in Figure 9. 546 599 Young’s modulus and the of Al/steel cast The mechanical properties for the Al/Fe bimetallic 547 600 bimetallic materials versus the volume fraction of the materials with AA1050 (99.5 wt.% Al) as the matrix 548 – 601 interconnected network of continuous wires. It is are shown in Table 1. The incorporation of 3 5 vol.% 549 of iron wires as reinforcement increases the Young’s 602 550 modulus, yield strength, and ultimate tensile strength, 603 551 but degrades the ductility. The Young’s modulus is 604 552 88 GPa and the specific stiffness is 30.3 GPa/(g/cm3) 605 553 for the Al/5 vol.% Fe bimetallic materials, which is 606 554 much higher than that of the monolithic Al alloys. 607 555 The measured Young’s modulus of the bimetallic Al/ 608 556 Fe materials exceeds the ROM prediction. This has 609 557 been attributed to the combined effect of redistribut- 610 558 611 ing the fiber stress from the three-dimensional inter- 559 612 connected nature and the limited presence of the 560 45 40 613 at the interface. Gupta et al. fabri- 561 614 cated aluminum-based bimetallic materials containing 562 615 particles and iron mesh (continuous) 563 616 Figure 7. Microstructures of the A356 alloys reinforced by reinforcement. Ti particles and the galvanized iron 564 617 a preform with entangled 304 stainless steel wire at wire mesh (0.4 vol.% zinc and 0.8 mm wire diameter) 565 40 618 17.7 vol.%. are utilized as the continuous/interconnected 566 619 567 620 568 621 569 622 570 623 571 624 572 625 573 626 574 627 575 628 576 629 577 630 578 631 579 632 580 Figure 8. (a) Young’s modulus and (b) density of Al-Si/steel cast bimetallic materials with an interconnected network of 633 581 continuous wires of stainless steel.36,41 634 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 7

635 phases on the interface. Bouayad et al.48 found that 688 636 689 several intermetallic compounds, including c-Al3FeSi, 637 690 g-Al5Fe2(Si), and b-Al5FeSi, can be formed at the 638 interface. The types of reaction products depend on 691 639 the times and temperatures. Kobayashi and Yakou49 692 640 reported that the common sequence to form the reac- 693 641 50 694 tion layer is Fe/Fe2Al5/FeAl3/Al, but Zhang et al. 642 showed that the sequence of the reaction layer is Fe/ 695 643 – 696 g-Al5Fe2(Si)/b-Al5FeSi/Al Si. The experimental results 644 have confirmed that the surface modification of alu- 697 645 698 minizing can promote the formation of sound surface 646 699 and metallurgical bonding between steel and Al, 647 Figure 9. Schematic diagram of two different reinforcement 700 preforms employed in Al/galvanized iron bimetallic materials.43 which can be achieved by compound casting. 648 701 Arghavani et al.51 found that the Zn coating on the 649 702 Table 1. Mechanical properties of aluminum reinforced with steel surface could enhance the wettability of bonding 650 44 703 galvanized iron. surface between steel and A5052 Al alloy. Liu 651 704 Ultimate Specific et al.52,53 found that the intermetallic compounds 652 Young’s Yield tensile stiffness 705 Al Fe Zn and Al FeZn are formed at the interface 653 modulus strength strength Ductility Density GPa/ 5 2 x 3 x 706 Materials (GPa) (MPa) (MPa) (%) (g/cm3) (g/cm3) between hot-dip galvanized steel and pure Al after 654 Al (matrix) 7062 10166 120631769 2.7 25.9 707 compound casting. Generally, the zincate must be at 655 Al/3vol.%Fe 7662 10862 13164563 2.92 26.1 708 Al/3vol.%Fe 8162 15264 186615 564 2.81 28.8 an appropriate thickness for the reaction during over- 656 709 Al/3vol.%Fe 8162 15066 173616 362 2.80 28.9 casting. If the thickness is more than the diffusion dis- 657 Al/5vol.%Fe 8861 10565 13066763 2.91 30.3 710 tance, the Zn layer will still exist in the final 658 With different wire arrangement. 711 659 microstructure after casting, which is detrimental to 712 660 the mechanical properties. This has been partially con- 713 reinforcement phase. The presence of reinforcement 54 661 firmed by Schwankl et al. showing that the interface 714 results in the 7.6% reduction in the coefficient of ther- 662 strength determined by zinc is the weakest part of the 715 mal expansion, the 10% increase in the Young’s 663 compound castings. If the coating is too thin, there 716 modulus, the 20% increase in the 0.2% yield strength, 664 are no sufficient compounds to provide bonding 717 and the 27% increase in the ultimate tensile strength. 665 strength. Therefore, the bonding interface between the 718 As the critical characteristics in manufacturing the 666 iron/steel and the aluminum alloy is the determining 719 bimetallic materials, the interface between steel/iron 667 factor for manufacturing the bimetallic materials. 720 and aluminum has been extensively studied through 668 721 different approaches due to the avoidance of forma- 669 46 2.4. Other Bimetallic Materials 722 670 tion of detrimental phases. The interfaces between 723 671 steel/iron and aluminum melt can be obtained by The Young’s modulus of Al-based bimetallic materials 724 672 immersing the steel/iron into aluminum melt or over- reinforced by other metals can be roughly estimated 725 673 casting aluminum melt onto the steel/iron surface. by the ROM model and the results are shown in 726 47 674 Dezellus et al. studied the formation of the interface Figure 10. Comparing with the Young’s modulus of 727 675 layer, by immersing mild steel into Al-Si alloy melts, Fe and Ni at a level of 200 GPa, the other continu- 728 676 and the mechanical properties of interface, by the ous reinforcement – such as W and Mo – has a 729 677 pushout test. The results showed that the Al5Fe2Si and higher potential for the improvement of stiffness. 730 678 Al9Fe2Si2 phases are formed at the interface and the However, the cost and processing procedure will 731 679 crack initiation would occur in the intermetallic reac- remain an issue in its application. 732 680 tion layer. The formation of the intermetallic layer 733 681 increases the mechanical properties of the bimetal- 734 3. Stiffness improvement in aluminum- 682 lic materials. 735 based composites 683 Viala et al.43 and Manasijevic et al.45 prepared iron 736 684 base insert reinforced Al-Si alloys by gravity casting Aluminum matrix composites reinforced with par- 737 685 and revealed that a continuous metallurgical bond at ticles, short fibers/whiskers, or continuous fibers have 738 686 the iron insert/Al-Si alloy interface can be achieved received considerable attention over the past decades 739

687 via the formation of FeAl3 and Fe2Al5 intermetallic due to the attractive properties resulting from the 740 8 S. AMIRKHANLOU AND S. JI

741 55–57 794 combination of their constituents. Al/TiB2, Al/ with substantial improvements in stiffness and 742 795 TiC, Al/ZrB2, Al/SiC, Al/AlN, Al/Al2O3, and Al/Mg2Si strength. However, a 50% increase in the Young’s 743 have been reported to be able to improve the Young’s modulus of Al alloys can be achieved by substituting a 796 – 744 modulus of cast Al alloys.58 60 The improvement of discontinuous reinforcement with continuous ones in 797 745 Young’s modulus in AMCs can be successfully AMCs.62 It is therefore capable of incorporating 798 746 achieved through a variety of casting processes, appropriate reinforcement in suitable volume fractions 799 747 including gravity casting, stirring casting, investment for casting aluminum components with improved 800 748 casting, , vacuum-assisted casting, semi- Young’s modulus and other technological properties 801 749 solid casting, and squeeze casting for manufacturing such as high thermal conductivity, high specific 802 750 shaped components, or making billets by direct chill strength, tailorable coefficient of , 803 751 casting for further processing such as forging, extru- improved strength, and low density, which is depend- 804 752 sion or rolling. ent upon the composition, grain size, microstructure, 805 753 The Young’s modulus of pure aluminum can be and fabrication process. 806 754 enhanced from 70 to 240 GPa by the reinforcement of The stiffness property of some reinforcement 807 19 755 60 vol.% continuous fiber.[ ] Similarly, the castings phases is listed in Table 2. These phases show the 808 756 809 of Al-9Si/20 vol.% SiCp composites significantly much-increased Young’s modulus and melting point 757 improve the Young’s modulus with the wear resist- in comparison with pure aluminum. In AMCs, the 810 758 ance equivalent or better than that of gray cast reinforcement phase can be formed by in-situ reaction 811 61 759 . Discontinuously reinforced AMCs have been or by ex-situ additions. In the specific condition, the 812 760 demonstrated to offer essentially isotropic properties in-situ particles can act as nucleating sites for grain 813 761 814 refinement or as strengthening phases to hinder dis- 762 65,66 815 location motion. Currently, several fabrication 763 816 methods including liquid state processing, deposition 764 817 process, and solid-state processing have been devel- 765 818 oped for the manufacture of AMCs. Figure 11 shows 766 819 the detailed casting process routes for manufacturing 767 820 AMCs, which include infiltration techniques,67,68 stir- 768 821 ring techniques,69,70 and rapid solidification.71,72 769 822 Liquid state processing is usually involved with the 770 823 casting process, which is energy-efficient and cost- 771 824 effective for massive production. Products of complex 772 825 shape can be formed directly through the melt mix- 773 826 ture with reinforcement. It is very attractive to pro- 774 827 duce as-cast components of AMCs with a uniform 775 828 reinforcement distribution of individual particles and 776 829 structural integrity. However, during solidification, the 777 830 particles ahead of the interface may get pushed, 778 831 ’ engulfed, or entrapped in the moving solidification 779 Figure 10. Young s modulus of aluminum-based bimetallic 832 materials reinforced with different types of metallic wires esti- front. The other difficulties in the casting process are 780 833 mated by rule of mixtures. the non-wettability of ex-situ particles by liquid metal, 781 834 782 – 835 Table 2. Properties of typical reinforcements.63 64 783 836 Melting Young’s Thermal conductivity Coff. of thermal 784 Reinforcement point (C) modulus (GPa) UTS (MPa) Density (g/cm3) (W/mK) expansion (106/K) 837

785 ZrB2 3246 350 6.09 140 7.4 838 786 AlN 2200 330 2,100 3.26 150 3.3 839 Al2O3 2043 380 2,070 3.15 30 7.0 787 TiC 3067 400 1,540 4.90 110 9.0 840 788 TiB2 3225 560 3,300 4.52 24 8.0 841 Mg Si 1102 120 4.50 4.4 7.5 789 2 842 ZrO2 2715 350 2,070 4.84 3.3 7.0 790 B4C 2763 425 2,690 2.35 39 3.5 843 SiC 2730 450 2,280 3.21 120 3.4 791 VC 2810 430 5.77 4.1 844 792 WC 2870 640 500 15.52 60 5.1 845 793 Si3N4 1900 207 530 3.18 28 1.5 846 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 9

847 900 848 901 849 902 850 903 851 904 852 905 853 906 854 907 855 908 856 909 857 910 858 911 859 912 860 913 861 914 862 915 863 Figure 11. Schematic diagram of processing methods of AMCs. 916 864 917 865 and the particle–Al interface interaction. Although the mathematical structure than that of the ROM or 918 866 addition of Ni, Mg, Li, Si, and Ca into Al melt can IROM. In this model, the modulus of elasticity and 919 867 improve wettability either by changing the interfacial the volume fraction of the components and the aspect 920 868 energy through some interfacial reaction or by modi- ratio (ratio of the geometric dimensions) of the 921 – 869 fying the oxide layer on the metal surface,73 75 the dif- reinforcement are taken into account. It has been 922 870 ficulty to obtain uniform dispersion of reinforcement widely reported that Halpin–Tsai model is more 923 871 particles is still an issue that hinders the adoption of accurate for particulate metal matrix composites. In 924 872 AMCs in industry.76,77 the Hashin and Shtrikman (H-S) theorem,86 the upper 925 873 In order to effectively improve the Young’s modu- bound rigorously corresponds to the composites con- 926 874 lus of AMCs, the generation of high modulus phases, taining the ‘soft’ inclusion matrix phase encapsulated 927 875 the reinforcement phases with covalent and ionic by a ‘stiffer’ reinforcement phase, while the lower 928 876 interatomic bonds in aluminum alloys are preferred bound corresponds to the composites with a ‘stiffer’ 929 877 approaches according to the nature of stiffness.78,79 inclusion reinforcement phase encapsulated by a 930 878 Therefore, the in-situ method is better than the ex-situ ‘softer’ matrix phase. The H-S bounds are tighter than 931 879 method because the wettability between the in-situ the ROM bounds and have been regarded as the best 932 880 formed phases and the aluminum matrix is signifi- possible bounds on properties for isotropic two-phase 933 881 cantly higher and is capable of forming clean and composites. The Tuchinskii model87 considers a two- 934 882 strong interfacial bonding in between.80,81 However, phase interpenetrating skeletal structure. The calcu- 935 883 the in-situ method is suitable for particulate-rein- lated value of modulus can be a good estimation of 936 884 forced AMCs because the in-situ techniques are not experimental guidance. However, this review will not 937 885 capable of making continuous fiber-reinforced AMCs. focus the modeling approaches and principles. Some 938 886 The Young’s modulus of composite materials can existing results from modeling are used to review the 939 887 be estimated by theoretical modeling, which depends experimental data. 940 888 on the morphological arrangement of materials com- 941 889 ponents. The most frequently used mathematical 942 3.1. Al/TiB2 Composites 890 models include: (a) the rule of mixtures (ROM) and 943 82 891 the inverse rule of mixtures (IROM), (b) the TiB2 is one of the most popular reinforcements for 944 892 Halpin–Tsai model,83 (c) the Hashin–Shtrikman high modulus AMCs because of its Young’s modulus 945 893 model,84 and (d) the Tuchinskii model.85 The ROM of 560 GPa and its easy synthesis using an in-situ pro- 946 87 894 (upper bound) and IROM (lower bound) can be cess. The in-situ formed TiB2 offers a better inter- 947 895 obtained according to the equal strain assumption and face with the aluminum matrix than the ex-situ added 948 16 88,89 896 the equal stress assumption, respectively. The elastic particles. The in-situ Al/TiB2 composites can be 949 897 properties of all of the composites are usually located synthesized using K2TiF6 and KBF4 salt reactions in 950 898 between the ROM upper and IROM lower bounds.86 molten Al;90 through a self-propagating high-tempera- 951 899 The Halpin–Tsai model has a more complicated ture synthesis (SHS) reaction via Al-Ti-B powder 952 10 S. AMIRKHANLOU AND S. JI

953 1006 954 1007 955 1008 956 1009 957 1010 958 1011 959 1012 960 1013 961 1014 962 1015 963 1016 964 Figure 12. (a) A SEM micrograph of the Al-9Si-1Mg-0.7Cu/TiB2 composite with 14 wt.% TiB2 particles and (b) a TEM micrograph 1017 showing the clean and well-bonded interface between the a-Al and TiB particles.102 965 2 1018 966 91–93 1019 compact/preform added to molten Al; through Mg), Si, and TiB phases in the microstructure. Lu 967 2 1020 the reaction of TiO -H BO -Na AlF with Al;94 or via et al.95 investigated the Al/TiB composite and found 968 2 3 3 3 6 2 1021 chemical reactions among Al, TiO , and B O par- that the Young’s modulus reaches 107 GPa by adding 969 2 2 3 1022 ticles.95 It is generally believed that the presence of a 15% TiB into the Al matrix. Obviously, the main rea- 970 2 1023 Al Ti phase in Al/TiB composites is beneficial for son for high stiffness properties is formation of high 971 3 2 1024 grain refinement but is detrimental to the mechanical volume fraction TiB with 565 GPa modulus. 972 2 1025 properties.96 The Al Ti can be eliminated during syn- 973 3 1026 thesis by the proper control of temperature, time, and 974 3.2. Al/TiC composites 1027 ratios of the raw materials.91,97 The presence of Si in 975 1028 cast Al alloys can improve the dispersion of TiB par- Titanium carbide (TiC) is a hard refractory ceramic 976 2 1029 ticles,98 although the TiB particles are still partially material with FCC crystal structures. The Young’s 977 2 1030 modulus is approximately 400 GPa and the shear 978 segregated in the eutectic regions because of the push- 1031 99–101 modulus is 188 GPa for the TiC,109,110 which is a 979 ing mechanism during solidification. The typical 1032 good candidate as reinforcement for improving stiff- 980 microstructure of Al/TiB2 composites is shown in 1033 ness of aluminum alloys111,112. Al/TiC in-situ compo- 981 Figure 12. The Al-9Si-1Mg-0.7Cu/TiB2 composite can 1034 sites can be synthesized by several techniques, 982 be produced with clean, smooth, and well-bonded 1035 983 interfaces between the aluminum matrix and TiB2 including: (a) the reaction of K2TiF6 salt and graphite, 1036 103 984 particles between 25 and 3,000 nm. (b) the direct reaction of Ti and C powders, (c) the 1037 985 The TiB2-reinforced AMCs can remarkably addition of Al-Ti-C powder into the Al melt, and (d) 1038 986 improve the mechanical properties, in particular the the reaction of CH4 gas with the Al-Ti melt. The reac- 1039 ’ 987 stiffness. The typical Young s modulus and other tions can be at a level of 1000 C for 30 minutes for 1040 113,114 988 mechanical properties of particulate-reinforced Al/ Al-4.5 Cu alloys. The in-situ formed TiC par- 1041 m 989 TiB2 composites are summarized in Table 3. The ticles can be smaller than 1 m in size or in a range 1042 ’ 115,116 990 increase of the Young s modulus of Al/TiB2 compo- of several micrometers. The formation of other 1043 991 sites can be up to 40% higher than that of pure alumi- phases, such as Al4C3 and Al3Ti phases, is considered 1044 106,107 116,117 992 num. The strength at elevated temperatures and to be unfavorable in Al/TiC composites. 1045 993 the wear and resistance can also have a signifi- On top of the enhancement of mechanical proper- 1046 108 102 994 cant increase. Kumar et al. reported an increase ties, the addition of TiC particles into aluminum melt 1047 995 of 108% in hardness, 123% in yield strength, 43% in has a dramatic improvement on the Young’s modulus, 1048 118 996 UTS, and 33% in Young’s modulus of the Al-7Si cast as shown in Figure 13. Samer et al. obtained the 1049 ’ ’ 997 alloy with 10 wt.% of TiB2, which provides a Young s Young s modulus of 106 GPa, the yield strength of 1050 998 modulus greater than 90 GPa. Han et al.108 studied 450 MPa, and the elongation of 6% in the composites 1051 999 the tensile properties of the Al-12Si alloy with 4 wt.% containing 22 vol.% TiC in pure Al. Mohapatra 1052 119 ’ 1000 TiB2 particles and found that the improvement of the et al. confirmed that the Young s modulus is 1053 1001 Young’s modulus can be observed in the temperature increased from 70 GPa of pure aluminum to 1054 1002 range of 25–350 C. Amirkhanlou et al.102 reported 88.78 GPa after adding 20 vol.% TiC. The mechanical 1055 1003 that Al-9Si-1Mg-0.7Cu/9 vol.% TiB2 can provide a properties of Al-4.5%Cu alloy reinforced with differ- 1056 1004 Young’s modulus greater than 94 GPa and the yield ent amounts of TiC are summarized in Table 4,in 1057 1005 strength up to 235 MPa by the formation of a-Al (Cu, which the addition of 10 wt.% TiC increases the 1058 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 11

104,105 1059 Table 3. Mechanical properties of Al/TiB2 cast composites synthesized by K2TiF6 and KBF4 salt reaction. 1112 1060 Materials Temperature (C) Young’s modulus (GPa) 0.2% Proof stress (MPa) UTS (MPa) Elongation (%) 1113

1061 Al-7Si/5 vol.% TiB2 25 83.0 126 175 7.00 1114 1062 Al-7Si/10 vol.% TiB2 25 92.0 152 209 4.60 1115 Al-12Si/4 wt.% TiB2 25 85.0 240 298 1.50 1063 Al-12Si/4 wt.% TiB2 200 80.0 189 233 3.00 1116 1064 Al-12Si/4 wt.% TiB2 350 66.0 84 96 5.80 1117 A356/2.1 vol.% TiB 25 72.9 209 235 7.81 1065 2 1118 A356/4.7 vol.% TiB2 25 76.3 212 252 7.36 1066 A356/8.4 vol.% TiB2 25 82.2 217 258 2.73 1119 1067 A356/2.1 vol.% TiB2 25 78.1 305 375 4.88 1120 A356/4.7 vol.% TiB2 25 80.2 317 377 1.90 1068 A356/8.4 vol.% TiB2 25 84.1 347 391 1.32 1121 1069 Al/5 vol.% TiB2 25 69.0 188 284 3.50 1122 Al/10 vol.% TiB2 25 84.0 249 326 1.92 1070 Al/5 vol.% TiB2 25 82.0 96 124 9.20 1123 1071 Al/10 vol.% TiB2 25 87.0 128 164 6.30 1124 Al/15 vol.% TiB2 25 91.0 124 153 5.50 1072 Al-Cu/10 vol.% TiB2 25 77.0 153 230 5.50 1125 1073 Al-Cu/10 vol.% TiB2 25 83.0 311 361 1.30 1126 Al/15 vol.% TiB 25 107.0 274 389 1.99 1074 2 1127 Al/15 vol.% TiB2 25 91.0 171 223 4.60 1075 Al-Cu/15 vol.% TiB2 25 93.0 248 333 2.30 1128 1076 1129 1077 121 1130 Young’s modulus to 99 GPa. In addition, the 1078 1131 Young’s modulus of the Al/TiC composite is close to 1079 1132 the upper limit calculated from the Hashin–Shtrikman 1080 122,123 1133 model, suggesting that the in-situ synthesis of 1081 1134 TiC particles to strong interfacial bonding and 1082 1135 the attendant load transfer. Despite the high stiffness of 1083 1136 Al/TiC in-situ composites, the porosity level and other 1084 1137 oxide impurities in the melt are the main concerns 1085 1138 because of the high synthesis temperature of 1086 1139 1000–1200 C. High temperature processing also results 1087 1140 in limitations for the industrial applications of in-situ 1088 1141 Al/TiC composites. 1089 1142 1090 3.3. Al/SiC Composites 1143 1091 1144 1092 SiC reinforcements are usually added into Al melt 1145 1093 through ex-situ additions incorporating with stirring Figure 13. Effect of TiC on the Young’s modulus of Al/ 1146 1094 or mixing.124,125 Casting routes can be gravity casting TiC composites. 1147 1095 and squeeze casting. Alternatively, the alloy is infil- 1148 trated into a porous preform formed by SiC reinforce- 1096 Young’s modulus of the AMCs with cast aluminum 1149 1097 ments. The wettability between the SiC reinforcements 1150 alloys can be enhanced to 114 GPa when the reinforce- 1098 and the aluminum alloy is a crucial concern in associ- 1151 ment is at a level of 20 vol.%. The castability is a sig- 1099 ation with the optimum fluidity of the alloy. One of 1152 nificant concern when the SiC addition is beyond this 1100 the main problems during the processing and casting 1153 level. For wrought aluminum alloys, the addition of 1101 of Al/SiC composites is that liquid aluminum attacks 1154 SiC reinforcement can be at a level of 25 vol.% for 1102 SiC reinforcements through chemical reaction, form- 1155 1103 ing Al C and Si.126,127 Particle clustering has greater casting and the subsequent plastic deformation process- 1156 4 3 ’ 1104 effects on the flow behavior and mechanical properties ing. The Young s modulus can be 140 GPa, which is 1157 ’ 1105 of Al/SiC AMCs because the particle clustering micro- double the Young s modulus of pure aluminum. 1158 1106 structure experiences a higher percentage of particle 1159 1107 fracture than that with particle random distribu- 3.4. Al/AlN Composites 1160 1108 tion.127,128 The stirring casting is an effective way to 1161 1109 promote the distribution of ex-situ particles.129,130 Aluminum nitride (AlN) has a Young’s modulus of 1162 1110 Table 5 summarizes the Young’s modulus and 310 GPa and therefore it can fairly increase the modu- 1163 1111 mechanical properties of ex-situ Al/SiC AMCs. The lus of aluminum castings.132,133 However, because of 1164 12 S. AMIRKHANLOU AND S. JI

1165 Table 4. Mechanical properties of Al matrix and Al-4.5Cu/TiC in-situ composites.120 1218 1166 Materials Vickers hardness (HV5) Young’s modulus (GPa) Yield strength (MPa) UTS (MPa) 1219 1167 Al-4.5%Cu 55.19 72.8 81.5 118 1220 1168 Al-4.5Cu/5wt.% TiC 61.12 83.4 95.7 134 1221 Al-4.5Cu/7wt.% TiC 69.43 91.8 103.4 156 1169 Al-4.5Cu/10wt.% TiC 75.76 98.7 117.3 179 1222 1170 1223 1171 1224 Table 5. Young’s modulus and mechanical properties of ex-situ Al/SiC AMCs.67,131 1172 1225 Materials Reinforcement Casting method Young’s modulus (GPa) Yield strength (MPa) UTS (MPa) Elongation (%) 1173 1226 Al-10Si-3Cu-1Mg-1.25Ni 10 vol.% SiC Gravity 88 359 372 0.3 1174 Al-10Si-3Cu-1Mg-1.25Ni 20 vol.% SiC Gravity 101 372 372 0.1 1227 1175 Al-9Si-0.5Mg 10 vol.% SiC Gravity 86 303 338 1.2 1228 Al-9Si-0.5Mg 20 vol.% SiC Gravity 99 338 359 0.4 1176 Al-10Si-1Fe-0.6 Mn 10 vol.% SiC Pressure die cast 91 221 310 0.9 1229 1177 Al-10Si-1Fe-0.6 Mn 20 vol.% SiC Pressure die cast 108 248 303 0.5 1230 Al-10Si-3.25Cu-1Fe-0.6 Mn 10 vol.% SiC Pressure die cast 94 241 345 1.2 1178 Al-3.25Cu-1Fe-0.6 Mn 20 vol.% SiC Pressure die cast 114 303 352 0.4 1231 1179 A356 10 vol.% SiC Casting 81 283 303 0.6 1232 A356 15 vol.% SiC Casting 90 324 331 0.3 1180 A356 20 vol.% SiC Casting 97 331 352 0.4 1233 1181 Al-12Si-Ni-Cu 20 vol.% SiC Squeeze casting 111 293 384 1234 1182 Al-7Si-Mg-Fe 15 vol.% SiC Gravity 98 183 280 1.0 1235 Al-3Mg 20 vol.% SiC Gravity 105 377 408 1.4 1183 Al-4.4Cu-Si-Mg 15 vol.% SiC Gravity 107 342 350 1.6 1236 1184 Al-7Si-0.3Mg 10 vol.% SiC Casting 82 287 308 0.6 1237 Al-7Si-0.3Mg 15 vol.% SiC Casting 91 329 336 0.3 1185 Al-7Si-0.3Mg 20 vol.% SiC Casting 98 336 357 0.4 1238 1186 A380 10 vol.% SiC Casting 95 245 332 1.0 1239 A380 20 vol.% SiC Casting 114 308 356 0.4 1187 AA6061 20 vol.% SiC Casting-forming 119 448 551 1.4 1240 1188 AA6061 20 vol.% SiC Casting- 108 414 545 2.0 1241 AA6061 20 vol.% SiC Casting-hot rolling 104 402 550 4.5 1189 AA2014 15 vol.% SiC Casting-forming 100 466 493 2.0 1242 1190 AA2024 20 vol.% SiC Casting-forming 110 465 620 2.0 1243 1191 AA2024 25 vol.% SiC Casting-forming 140 470 800 2.0 1244 AA2024 15 vol.% SiC Casting-hot rolling 96 530 2.4 1192 AA2024 15 vol.% SiC Casting-hot rolling 110 330 1.2 1245 1193 AA2618 12 vol.% SiC Casting-forming 98 460 532 3.0 1246 AA2124 17.8 vol.% SiC Casting-forming 100 400 610 6.0 1194 AA2124 20 vol.% SiC Casting-forming 105 405 560 7.0 1247 1195 AA2124 25 vol.% SiC Casting-forming 116 490 630 3.0 1248 AA7075 15 vol.% SiC Casting-forming 95 556 601 3.0 1196 AA7075 15 vol.% SiC Casting-forming 90 598 643 2.0 1249 1197 AA7075 20 vol.% SiC Casting-forming 105 665 735 2.0 1250 AA8090 13 vol.% SiC Casting-forming 101 455 520 4.0 1198 AA8090 13 vol.% SiC Casting-forming 101 499 547 3.0 1251 1199 AA8090 17 vol.% SiC Casting-forming 105 310 460 5.5 1252 1200 AA8090 17 vol.% SiC Casting-forming 105 450 540 3.5 1253 1201 1254 1202 the low thermal expansion and good thermal conduct- Table 6. Young’s modulus and shear modulus of reinforced 1255 138 1203 ivity, Al/AlN is attractive in some specific applica- and non-reinforced materials. 1256 1204 tions. In-situ Al/AlN composites are usually made by Young’s modulus (GPa) Shear modulus (GPa) 1257 Al-4Cu-1Mg 72.9 27.1 1205 a direct reaction between N2 and/or NH3 gas with the 1258 134,135 Al-4Cu-1Mg/45% AlN 146.3 56.5 1206 molten aluminum alloys. The nitridation of Al is Al-1Mg-0.5Si 72.5 27.1 1259 1207 a thermodynamically exothermic process and is ener- Al-1Mg-0.5Si/42% AlN 141.3 54.6 1260 Al-3Mg 71.3 26.6 1208 getically favorable over an extensive temperature Al-3Mg/48% AlN 149.5 58.2 1261 1209 range. The formed AlN particles are smaller than 10 1262 1210 mm and show a hexagonal morphology.136,137 The 1263 1211 AlN particles can be less than 2 mm in the Al/AlN composites can significantly improve the mechanical 1264 139 1212 composites synthesized by adding NH3 into the melt properties, as shown in Table 6. Balog studied Al/ 1265 1213 in the temperature range from 1,100 to 1,270 C.138 In AlN AMCs with cold isostatic pressing (CIP) and 1266 1214 comparison with the purified N2 bubbling gas, NH3 extrusion, and the results are shown in Figure 14. The 1267 1215 can enhance the formation of the AlN phase in alumi- Young’s modulus is significantly increased when 1268 1216 num melt.137 Chedru139 studied ex-situ Al/AlN AMCs increasing the content of AlN in the AMCs. However, 1269 1217 with squeeze casting and found that Al/AlN the studies for castable materials are still very limited 1270 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 13

1271 1324 1272 1325 1273 1326 1274 1327 1275 1328 1276 1329 1277 1330 1278 1331 1279 1332 1280 1333 1281 1334 1282 1335 1283 1336 1284 1337 1285 Figure 14. Ultimate tensile strength (UTS), yield strength, and 1338 Young’s modulus of Al-AlN nanocomposites prepared by CIP Figure 15. SEM image of the Al/ZrB2-Al3Zr hybrid 140 143 1339 1286 with subsequent extrusion. composite. 1287 1340 1288 1341 due to high temperature manufacturing methods for fraction of ZrB2 particles increases. The main 1289 in-situ Al/AlN composites. challenge for fabrication of high modulus in-situ 1342 1290 composites by casting processes is volume fraction of 1343 1291 1344 3.5. Al/ZrB -Al Zr Composites reinforcement. In fact, it is difficult to form high 1292 2 3 volume fraction of particles through salt reaction or 1345 1293 1346 Al/ZrB2-Al3Zr composites use the hybrid reinforce- direct reaction between the gases with the molten 1294 ’ 1347 ment phases of ZrB2 and Al3Zr. The Young s modulus aluminum alloys. 1295 1348 is 350 GPa for ZrB2 and 205 GPa for Al3Zr. Al/ZrB2- 1296 1349 Al Zr in-situ composites are usually synthesized by 1297 3 3.6. Other Particulate-reinforced AMCs 1350 the addition of K ZrF and KBF salts to Al melt.141 1298 2 6 4 1351 Zhang et al.142 synthesized in-situ ZrB and Al Zr par- The other typical reinforcements listed in Table 2 are 1299 2 3 1352 ticles in A356 alloy with K ZrF and KBF salts. The capable of being synthesized by in-situ reactions. 1300 2 6 4 1353 ZrB and Al Zr particles are from 0.3 to 0.5 mm, as However, the compounds with high modulus are 1301 2 3 1354 shown in Figure 15. Zhao et al.144 reported that the more attractive. In addition to that described in the 1302 1355 morphologies of Al Zr are sensitive to the temperature previous section, Al2O3, WC, B4C, and VC are also 1303 3 1356 of the Al melt. When the temperatures change from good candidates for improving the Young’s modulus 1304 1357 of aluminum composites. For example, the in-situ Al/ 1305 850 to 1000 C, the morphologies of the Al3Zr par- 1358 Al O composites can be synthesized by: (a) the direct 1306 ticles can be spherical shape, tetragon shape, rod 2 3 1359 melt oxidation of aluminum alloys at high tempera- 1307 shape, and fiber shape, but the ZrB2 particles show no 1360 obvious diversity in morphology. The particulate-rein- ture,153 (b) directly passing into the aluminum 1308 154 1361 1309 forced Al/ZrB2-TiB2 composites can also be formed melt to form Al2O3, and (c) the displacement reac- 1362 1310 by the addition of KBF4,K2ZrF6, and K2TiF6 salts tions between metal oxides and aluminum to produce 1363 145,146 1311 into Al melt, by which the formed TiB2 and Al2O3 particulate reinforcement. However, the experi- 1364 ’ 1312 ZrB2 particles are hexagonal with the average size less mental evidence for the improvement of Young s 1365 m 147 1313 than 2 m. modulus in those in-situ AMCs is not sufficient. 1366 1314 The Al/ZrB2-Al3Zr composites show valuable The manufacture and the properties of ex-situ 1367 1315 improvement in stiffness, strength, and wear proper- AMCs have been comprehensively reviewed by 1368 148,149 31 1316 ties with the increase in ZrB2 contents. As Rohatgi et al. Al/SiC and Al/TiB2 have also been dis- 1369 150 1317 shown in Figure 16, Selvam and Dinaharan verified cussed in the present paper. The other ex-situ AMCs 1370 1318 the stiffness improvement of 7075/ZrB2 composite, processed by casting methods are shown in Table 7.It 1371 1319 which is further attributed to ZrB2 that has a covalent is possible to combine up to 20 vol.% of A12O3 into 1372 1320 interatomic bond and high intrinsic modulus. different aluminum alloys for improving the Young’s 1373 1321 However, Gautam et al.151,152 found that the improve- modulus. The dominant factors in controlling the 1374 ’ ’ 1322 ment of the Young s modulus in Al/ZrB2-Al3Zr Young s modulus of ex-situ AMCs are the type, shape, 1375 1323 hybrid composite is insignificant when the volume volume fraction, and distribution of reinforcement 1376 14 S. AMIRKHANLOU AND S. JI

1377 1430 1378 1431 1379 1432 1380 1433 1381 1434 1382 1435 1383 1436 1384 1437 1385 1438 1386 1439 1387 1440 1388 1441 1389 1442 1390 1443

1391 Figure 16. Stress–strain graphs showing: (a) the effect of ZrB2 content in AA7075/ZrB2 in-situ composites and (b) the effect of 1444 in-situ 149 150 1392 ZrB2 and Al3Zr content in AA5052/ZrB2-Al3Zr composites. , 1445 1393 1446 1394 Table 7. Young’s modulus and mechanical properties of Al-based particulate ex-situ composites.19,66,130 1447 1395 Materials Reinforcement Casting method Young’s modulus (GPa) YS (MPa) UTS (MPa) Elongation (%) 1448

1396 Al-12Si-Ni-Cu 20 vol.% Al2O3 Squeeze casting 95 210 297 1449 1397 Al-4.2Cu-1.4Mg-0.6Ag 25 vol.% Al2O3 Stir casting-forming 97 450 460 0.5 1450 Al-4Cu-1Mg-0.5Ag 15 vol.% Al2O3 Stir casting-forming 90 414 510 1.3 1398 A201 20 vol.% TiC Stir casting-forming 105 420 2.0 1451 1399 AA6061 10 vol.% Al2O3 Stir casting-forming 81 297 338 7.6 1452 AA6061 15 vol.% Al2O3 Stir casting-forming 88 386 359 5.4 1400 AA6061 20 vol.% Al2O3 Stir casting-forming 99 359 379 2.1 1453 1401 AA6061 15 vol.% Al2O3 Casting-forming 91 342 364 3.2 1454 AA6061 15 vol.% Al2O3 Casting-forming 98 405 460 7.0 1402 AA6061 20 vol.% Al2O3 Casting-forming 105 420 500 5.0 1455 1403 AA6061 25 vol.% Al2O3 Casting-forming 115 430 515 4.0 1456 AA2014 10 vol.% Al O Stir casting-forming 84 483 517 3.3 1404 2 3 1457 AA2014 15 vol.% Al2O3 Stir casting-forming 92 476 503 2.3 1405 AA2014 20 vol.% Al2O3 Stir casting-forming 101 483 503 0.9 1458 1406 1459 1407 1460 1408 phases. The porosity and other microstructural char- reinforcement should be precisely controlled. Also, 1461 1409 acteristics are also critical for property improve- secondary mechanical deformation will result in an 1462 1410 ment.155,156 The presence of matrix–particle improvement of ductility. In the presence of strong 1463 1411 decohesion, particle cracking, and void growth can interfacial bonding, effective load transfer from the 1464 1412 decrease the load transfer capability of the interface matrix to the reinforcement is enhanced, leading to 1465 1413 and, consequently, decrease the Young’s modulus of good ductility and damage resistance. 1466 1414 the AMCs. The subsequent mechanical processes are 1467 1415 an effective approach to enhance the quality of the 3.7. AMCs with Continuous Reinforcement 1468 1416 interface between matrix and reinforcement in ex-situ 1469 1417 cast composites as well as the distribution of high Al alloys reinforced with continuous ceramic 1470 1418 modulus particles, as shown in Table 7. Secondary reinforcement, such as SiC and Al2O3, can be consid- 1471 1419 plastic deformation is not capable of altering the ered as alternative materials to achieve outstanding 1472 14 1420 Young’s modulus of AMCs; however, these proc- and modulus. The Al/SiCp and Al/ 1473 1421 esses can improve the toughness of the composites. Al2O3 composites can be produced by the molten alu- 1474 1422 The main concern on the Young’s modulus of ex- minum infiltration techniques, such as pressure- 1475 1423 situ AMCs is their tendency to have relatively low assisted, vacuum-driven, and pressureless or capillar- 1476 1424 ductility and fracture toughness, as shown in Table 7. ity-driven processes. Aghajanian et al.67,157 reported 1477 1425 The damage mechanism of ex-situ AMCs is mainly the pressureless infiltration technique, by which the 1478 1426 the reinforcement fracture and decohesion at the aluminum alloys infiltrated the reinforcement pre- 1479 1427 matrix/reinforcement interface. To achieve acceptable forms spontaneously in a nitrogen atmosphere. This 1480 1428 ductility and toughness, the composition, heat treat- method is believed to be a cost-effective, nearly net 1481 1429 ment process, size and shape distribution of the shape technique with the combined processing of 1482 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 15

1483 materials and shaping of the components simultan- Young’s modulus of AMCs are the volume fraction, 1536 1484 eously. The basic problem encountered in the fabrica- aspect ratio, and the interface. The bonding between 1537 1485 tion of these composites is the rejection of the the matrix and the reinforcement is the most import- 1538 1486 ceramic phase by the liquid metal due to their lack of ant factor in determining mechanical properties. 1539 1487 wettability.158 To improve the wetting of ceramics by Strong interfacial bonding provides effective load 1540 1488 liquid metals, a possible approach is to apply a metal transfer from the matrix to the reinforcement for 1541 1489 coating on the ceramic particles, which essentially improved Young’s modulus and other mechanical 1542 1490 increases the overall surface energy of the solid, properties. The main concern on the performance of 1543 1491 thereby promoting wetting by the liquid metal. AMCs is their tendency to have relatively low ductility 1544 1492 Although the continuous ceramic reinforcement/fibers and fracture toughness when the materials provide 1545 1493 can provide 210 GPa Young’s modulus,159 they usually high modulus. When using particulate-reinforced 1546 1494 1547 suffer from very low ductility – less than 0.2 – AMCs, the castability should be considered due to 1495 1548 restricting their applications. Moreover, it is difficult challenges in casting components with complex shape 1496 1549 to make shaped castings. and cavity. The balance of castability/processibility 1497 1550 and the improvement in Young’s modulus is the key 1498 1551 for further development. 1499 4. Summary and future outlook 1552 Bimetallic materials, made by metal wires with cast 1500 1553 The Young’s modulus of aluminum-based materials is aluminum alloys, are effective for modulus improve- 1501 1554 one of the most important mechanical properties in ment. In fact, bimetallic materials can be considered a 1502 1555 controlling structural performance. The improvement special type of . The preforms 1503 1556 of the Young’s modulus of castable aluminum-based made by continuous metallic wires as skeletons or 1504 1557 materials is essential for increasing their competive- frames are a key step. The pretreatment of the surfa- 1505 1558 ness in light weighting structural applications. The ces is needed before casting. The overcasting can be 1506 1559 capability of making complex shaped castings of these 1507 any of the conventional casting methods. Knowledge 1560 materials is critical in considering the massive produc- 1508 in this area has not been well established for the var- 1561 tion and the application in industry. The castability 1509 iety of preform structures, pretreatments, and casting 1562 depends on the introduction methods, processing 1510 conditions; so continued study is necessary. 1563 1511 methods, volume fraction, size, and distribution of the Stiff aluminum alloys are potentially one of the 1564 1512 high modulus phases. The influence of alloying ele- most promising materials for the significant reduction 1565 ’ 1513 ments on the Young s modulus depends on the state. of structural weight with satisfied mechanical proper- 1566 ’ 1514 If the alloying elements are in a solid solution phase, ties, including the Young s modulus. There are some 1567 ’ 1515 the magnitude of the Young s modulus is determined knowledge gaps and challenges for the further devel- 1568 1516 by the nature of the atomic interactions. If the alloy- opment of high modulus cast aluminum alloys, 1569 1517 ing elements form second phases, the magnitude of which include: 1570 ’ 1518 the Young s modulus is determined by the volume 1571 ’ 1519 fraction and the intrinsic modulus of the second a. The Young s modulus of aluminum alloys with 1572 ’ 1520 phase. Overall, the increase of Young s modulus in multiple components is not fully understood. The 1573 1521 conventional cast aluminum alloys is usually less than development of complex Al-based alloys with the 1574 1522 15% through adding alloying elements for manufac- addition of desirable alloying elements is needed to 1575 1523 turing complex shaped castings. Therefore addition of ensure both high modulus and ductility properties. 1576 1524 ceramic particles and reinforcement is necessary for b. Up to now, the main purpose for the addition of 1577 1525 significant improvement of the stiffness of Al alloys. high modulus phase/reinforcement into the Al 1578 1526 The improvement of the Young’s modulus through alloys has been to improve the wear resistance 1579 1527 introducing high modulus reinforcement phases as and high temperature performance. It is very 1580 1528 AMCs is an effective approach because of their high important to carefully and specifically select the 1581 1529 Young’s modulus. The most capable reinforcement type as well as the volume fraction of reinforce- 1582 ¼ ¼ 1530 phases are TiB2 (E 560 GPa) and SiC (E 480 GPa) ment for modulus improvement. 1583 1531 for making shaped castings. Reinforcement phases can c. Careful selection and combination of desirable 1584 1532 be added by ex-situ or in-situ methods, in which the alloying elements and in-situ formed reinforce- 1585 1533 in-situ method with particulate reinforcement is pre- ment would possibly be the preferred option for 1586 1534 ferred for making castings with relatively complex developing the material with dominant stiffness 1587 1535 shape and cavity. The main factors governing the properties, toughness, and good castability. 1588 16 S. AMIRKHANLOU AND S. JI

1589 d. In bimetallic materials, reactivity between the aluminum cold deformed by tension test, Rev. Metal. 1642 1590 reinforcement and the aluminum matrix must be Madrid. 34, 310–313 (1998). 1643 1591 14. A. Villuendas, J. Jorba, and A. Roca, The role of pre- 1644 carefully controlled to avoid the formation of ’ 1592 cipitates in the behavior of Young s modulus in alu- 1645 brittle interface, which tends to lower the tough- minium alloys, Metall. Mater. Trans. A. 45(9), 1593 1646 ness of the interface. Bimetallic materials can be 3857–3865 (2014). 1594 considered for local stiffness improvement of the 15. I. Polmear, D. St John, J. F. Nie, and M. Qian, Light 1647 1595 aluminum components. Alloys: Metallurgy of the Light Metals. Butterworth- 1648 1596 Heinemann (2017). Q3 1649 1597 16. D. Hull and T. Clyne, An Introduction to Composite 1650 1598 Disclosure statement Materials, Cambridge University Press (1996). 1651 17. A. Nieto, A. Bisht, D. Lahiri, and A. Agarwal, 1599 No potential conflict of interest was reported by Graphene reinforced metal and ceramic matrix com- 1652 1600 Q1 the authors. posites: a review, Int. Mater. Rev. 62, 241–302 1653 1601 (2017). 1654 1602 18. S. C. Tjong and Z. Y. Ma, Microstructural and 1655 Funding 1603 mechanical characteristics of in situ metal matrix 1656 – 1604 Financial support from Jaguar Land Rover (JLR) [grant composites, Mater. Sci. Eng. R. 29,49 113 (2000). 1657 number R33232] is gratefully acknowledged. 19. I. Ibrahim, F. Mohamed, and E. Lavernia, Particulate 1605 reinforced metal matrix composites-a review, J. 1658 1606 Mater. Sci. 26, 1137–1156 (1991). 1659 1607 References 20. R. Jamaati, S. Amirkhanlou, M. R. Toroghinejad, 1660 1608 and B. Niroumand, CAR process: a technique for 1661 1609 1. W. S. Miller, L. Zhuang, J. Bottema, A. Wittebrood, significant enhancement of as-cast MMC properties, 1662 P. De Smet, A. Haszler, and A. Vieregge, Recent Mater. Charac. 62, 1228–1234 (2011). 1610 1663 development in alloys for the automotive 21. S. Amirkhanlou, R. Jamaati, M. R. Toroghinejad, 1611 industry, Mater. Sci. Eng. A. 280(1), 7–49 (2000). and B. Niroumand, Manufacturing of high-perform- 1664 1612 2. T. Dursun and C. Soutis, Recent developments in ance Al356/SiCp composite by CAR process, Mater. 1665 1613 advanced aircraft aluminium alloys, Mater. Des. 56, Manuf. Process. 26, 902–907 (2011). 1666 1614 862–871 (2014). 22. F. Lasagni and H. P. Degischer, Enhanced Young’s 1667 1615 3. D. J. Lloyd, Particle reinforced aluminium and mag- modulus of Al-Si alloys and reinforced matrices by 1668 co-continuous structures, J. Compos. Mater. 44, 1616 nesium matrix composites, Int. Mater. Rev. 39(1), 1669 1–23 (1994). 739–755 (2010). 1617 4. J. G. Kaufman and E. L. Rooy, Aluminium alloy 23. T. Clyne and J. Mason, The squeeze infiltration pro- 1670 1618 castings: properties, processes, and applications, cess for fabrication of metal-matrix composites, 1671 – 1619 Q2 ASM International. 2004. Metall. Trans. A. 18(8), 1519 1530 (1987). 1672 1620 5. F. Bonnet, V. Daeschler, and G. Petitgand, High 24. M. Acilar and F. Gul, Effect of the applied load, slid- 1673 1621 modulus : new requirement of automotive mar- ing distance and oxidation on the dry sliding wear 1674 behaviour of Al–10Si/SiCp composites produced by 1622 ket. How to take up challenge?, Can. Metall. Q. 53, 1675 – vacuum infiltration technique. Mater. Des. 25(3), 1623 243 252 (2014). – 1676 6. V. S. Zolotorevsky, N. A. Belov, and M. V. Glazoff, 209 217 (2004). 1624 25. Y. Zhang, S. Ji, G. Scamans, and Z. Fan, Interfacial 1677 Casting Aluminium Alloys, Elsevier, Oxford (2007). characterisation of overcasting a cast Al-Si-Mg 1625 7. P. K. Rohatgi, Metal matrix composites, Def. Sci. J. 1678 (A356) alloy on a wrought Al-Mg-Si (AA6060) alloy, 1626 43(4), 323–349 (2013). 1679 J. Mater. Process. Technol. 243, 197–204 (2017). 1627 8. A. Mortensen and J. Llorca, Metal matrix compo- 1680 26. X. L. Xie, Y. W. Mai, and X. P. Zhou. Dispersion sites, Annu. Rev. Mater. Res. 40, 243–270 (2010). 1628 and alignment of carbon nanotubes in polymer 1681 9. S. R. Bakshi, D. Lahiri, and A. Agarwal, Carbon 1629 matrix: a review, Mater. Sci. Eng. R. 49,89–112 1682 nanotube reinforced metal matrix composites-a 1630 – (2005). 1683 review, Int. Mater. Rev. 55,41 64 (2010). 27. H. Porwal, S. Grasso, and M. J. Reece, Review of 1631 10. K. L. Kendig and D. B. Miracle, Strengthening mech- 1684 1632 graphene-ceramic matrix composites, Adv. Appl. 1685 anisms of an Al-Mg-Sc-Zr alloy, Acta Mater. 50(16), Ceram. 112(8), 443–454 (2013). – 1633 4165 4175 (2002). 28. X. Zhang, W. Chen, H. Luo, and T. Zhou, 1686 1634 11. K. Masuda-Jindo and K. Terakura, Electronic theory Formation of periodic layered structure between 1687 1635 for solid-solution hardening and softening of dilute novel Fe-Cr-B cast steel and molten aluminium, 1688 1636 Al based alloys: elastic-moduli enhancement of Al-Li Scripta Mate. 130, 288–291 (2017). 1689 1637 alloys, Phys. Rev. B. 39(11), 7509 (1989). 29. S. V. Nair, J. K. Tien, and R. C. Bates. Sic-reinforced 1690 12. W. H. Wang, The elastic properties, elastic models 1638 aluminium metal matrix composites, Inter. Met. Rev. 1691 and elastic perspectives of metallic glasses, Prog. 30(1), 275–290 (1985). 1639 Mater. Sci. 57, 487–656 (2012). 30. T. Christman and S. Suresh, Microstructural devel- 1692 1640 13. M. Lucena, J. A. Benito, A. Roca, and J. Jorba, opment in an aluminium alloy-SiC whisker compos- 1693 1641 Changes of elastomechanic constants of pure ite, Acta Metall. 36(7), 1691–1704 (1988). 1694 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 17

1695 31. P. K. Rohatgi, R. Asthana, and S. Das, Solidification, alloy & austenitic cast iron insert, Int. J. Met. 9, 1748 1696 structures, and properties of cast metal-ceramic par- 27–32 (2015). 1749 1697 ticle composites, Inter. Met. Rev. 31(1), 115–139 46. F. Haddadi, Microstructure reaction control of dis- 1750 1698 (1986). similar automotive aluminium to galvanized steel 1751 32. F. Boland, C. Colin, C. Salmon, and F. Delannay, sheets ultrasonic spot , Mater. Sci. Eng. A. 1699 1752 Tensile flow properties of Al-based matrix compo- 678,72–84 (2016). 1700 sites reinforced with a random planar network of 47. O. Dezellus, B. Digonnet, M. Sacerdote-Peronnet, F. 1753 1701 continuous metallic fibres, Acta Mater. 46(18), Bosselet, D. Rouby, and J. C. Viala, Mechanical test- 1754 1702 6311–6323 (1998). ing of steel/aluminium- interfaces by pushout, 1755 1703 33. L. Ryelandt, C. Salmon, and F. Delannay, Neutron Int. J. Adhes. 27, 417–421 (2007). 1756 1704 diffraction analysis of the evolution of phase stresses 48. A. Bouayad, C. Gerometta, A. Belkebir, and A. 1757 during plastic straining of aluminium matrix compo- Ambari, Kinetic interactions between solid iron and 1705 sites reinforced with a continuous, random planar molten aluminium, Mater. Sci. Eng. A. 363,53–61 1758 1706 network of fibres, Mater. Sci. Forum. 347–349, (2003). 1759 1707 486–491 (2000). 49. S. Kobayashi and T. Yakou, Control of intermetallic 1760 1708 34. Q. Tan, X. Tong, H. Lu, D. Zhang, and J. Hong, compound layers at interface between steel and alu- 1761 1709 Mechanical behaviours of quasi-ordered entangled minium by diffusion-treatment, Mater. Sci. Eng. A. 1762 – 1710 aluminium alloy wire material, Mater. Sci. Eng. A. 338,44 53 (2002). 1763 527(1-2), 38–44 (2009). 50. K. Zhang, X. Bian, Y. Li, Y. Liu, and C. Yang, New 1711 35. C. Salmon, F. Boland, C. Colin, and F. Delannay, evidence for the formation and growth mechanism 1764 1712 Mechanical properties of aluminium/Inconel 601 of the intermetallic phase formed at the Al/Fe inter- 1765 1713 composite wires formed by swaging, J. Mater. Sci. face, J. Mater. Res. 95, 3279–3287 (2013). 1766 1714 33(23), 5509–5516 (1998). 51. M. R. Arghavani, M. Movahedi, and A. H. Kokabi, 1767 1715 36. Q. Tan and G. He, 3D entangled wire reinforced Role of zinc layer in resistance spot welding of alu- 1768 metallic composites, Mater. Sci. Eng. A. 546, minium to steel, Mater. Des. 102, 106–114 (2016). 1716 1769 233–238 (2012). 52. Y. Liu, X. Bian, K. Zhang, C. Yang, L. Feng, H. S. 1717 37. V. Ganesh, C. Lee, and M. Gupta, Enhancing the Kim, and J. Guo, Interfacial microstructures and 1770 1718 tensile modulus and strength of an aluminium alloy properties of aluminium alloys/galvanized low-car- 1771 1719 using interconnected reinforcement methodology, bon steel under high-pressure torsion, Mater. Des. 1772 1720 Mater. Sci. Eng. A. 333(1), 193–198 (2002). 64, 287–293 (2014). 1773 1721 38. C. Salmon, D. Tiberghien, R. Molins, C. Colin, and 53. T. Liu, Q. Wang, Y. Sui, et al, An investigation into 1774 F. Delannay, Influence of the oxidation conditions of aluminium–aluminium bimetal fabrication by 1722 the fibres on the mechanical properties of Al matrix squeeze casting, Mater. Des. 68,8–17 (2015). Q41775 1723 composites reinforced with Ni-based fibres, Mater. 54. M. Schwankl, J. Wedler, and C. Korner,€ Wrought 1776 1724 Sci. Forum. 369–372, 435–442 (2001). Al-Cast Al compound casting based on zincate treat- 1777 1725 39. C. Salmon, C. Colin, R. Molins, and F. Delannay, ment for aluminium wrought alloy inserts, J. Mater. 1778 1726 Strengthening of Al/Ni-based composites by in situ Process. Technol. 238, 160–168 (2016). 1779 1727 growth of intermetallic particles, Mater. Sci. Eng. A. 55. S. L. Pramod, S. R. Bakshi, and B. S. Murty, 1780 334(1), 193–200 (2002). Aluminum-based cast in situ composites: a review, J. 1728 40. M. Gupta, M. O. Lai, and C. Y. H. Lim, Mater. Eng. Perform. 24, 2185–2207 (2015). 1781 1729 Development of a novel hybrid aluminium-based 56. S. Amirkhanlou and B. Niroumand, Fabrication and 1782 1730 composite with enhanced properties, J. Mater. characterization of Al356/SiCp semisolid composites 1783 – – 1731 Process Technol. 176(1 3), 191 199 (2006). by injecting SiCp containing composite powders, J. 1784 – 1732 41. F. Boland, C. Colin, and F. Delannay, Control of Mater. Process. Technol. 212, 841 847 (2012). 1785 interfacial reactions during liquid phase processing 57. S. S. Sidhu, S. Kumar, and A. Batish. Metal matrix 1733 1786 of aluminium matrix composites reinforced with composites for thermal management: a review, Crit. 1734 INCONEL 601 fibers, Metall. Mater. Trans. A. 29(6), Rev. Solid State Mater. Sci. 4, 132–157 (2016). 1787 1735 1727–1739 (1998). 58. B. V. Ramnath, C. Elanchezhian, R. M. Annamalai, 1788 1736 42. K. Guler, A. Kisasoz, and A. Karaaslan, Investigation S. Aravind, T. S. A. Atreya, V. Vignesh, and C. 1789 1737 of Al/Steel bimetal composite fabrication by vacuum Subramanian, Aluminium metal matrix composites – 1790 – 1738 assisted solid mould investment casting, Acta Phys a review. Rev Adv Mater Sci. 2014;38:55 60. 1791 Polonica A. 126(6), 1327–1330 (2014). 59. K. Tian, Y. Zhao, L. Jiao, S. Zhang, Z. Zhang, and X. 1739 1792 43. J. Viala, M. Peronnet, F. Barbeau, F. Bosselet, and J. Wu, Effects of in situ generated ZrB2 nano-particles 1740 Bouix, Interface chemistry in aluminium alloy cast- on microstructure and tensile properties of 2024 Al 1793 1741 ings reinforced with iron base inserts, Compos. Part matrix composites, J. Alloys Comp. 594,1–6 (2014). 1794 1742 A. 33, 1417–1420 (2002). 60. R. Jamaati, S. Amirkhanlou, M. R. Toroghinejad, 1795 1743 44. V. Ganesh and M. Gupta, Effect of the extent of and B. Niroumand, Comparison of the microstruc- 1796 1744 reinforcement interconnectivity on the properties of ture and mechanical properties of as-cast A356/SiC 1797 an aluminium alloy, Scripta Mater. 44(2), 305–310 MMC processed by ARB and CAR methods, J. 1745 (2001). Mater. Eng. Perform. 21(7), 1249–1253 (2012). 1798 1746 45. S. Manasijevic, R. Radisa, Z. Z. Brodarac, N. Dolic, 61. K. U. Kainer, Basics of Metal Matrix Composites in 1799 1747 and M. Djurdjevic, Al-Fin bond in aluminium Book: Metal Matrix Composites: Custom-made 1800 18 S. AMIRKHANLOU AND S. JI

1801 Materials for Automotive and Aerospace Engineering, temperature strength to cast AlSi10Cu5Ni1-2 piston 1854 1802 Q5 1–54 (2006). alloys, Acta Mater. 59(16), 6420–6432 (2011). 1855 1803 62. K. K. Chawla, Metal Matrix Composites, Wiley 78. H. Springer, R. Aparicio Fernandez, M. J. Duarte, 1856 1804 Online Library (2006). et al. Microstructure refinement for high modulus 1857 63. J. Zhang and Z. Fan, Microstructure and mechanical 1805 in-situ metal matrix composite steels via controlled 1858 properties of in situ Al-Mg2Si composites. Mater. solidification of the system Fe-TiB2, Acta Mater. 96, 1806 Sci. Technol. 16(7–8), 913–918 (2000). 47–56 (2015). 1859 1807 64. K. U. Kainer, Metal Matrix Composites: Custom- 79. H. Zhang, H. Springer, R. Aparicio-Fernandez, et al. 1860 1808 made Materials for Automotive and Aerospace Improving the mechanical properties of Fe-TiB2 high 1861 1809 Engineering, John Wiley & Sons (2006). modulus steels through controlled solidification 1862 1810 65. J. Mathew, A. Mandal, and S. D. Kumar, Effect of processes, Acta Mater. 118, 187–195 (2016). 1863 semi-solid forging on microstructure and mechanical 1811 80. Q. Gao, et al. Improvement of particles distribution 1864 properties of in-situ cast Al-Cu-TiB2 composites, J. of in-situ 5 vol% TiB particulates reinforced Al-4.5 1812 – 2 1865 Alloys Comp. 712, 460 467 (2017). Cu alloy matrix composites with ultrasonic vibration 1813 66. Z. Fan, Y. Wang, Y. Zhang, T. Qin, X. R. Zhou, treatment, J. Alloys Comp. 692,1–9 (2017). 1866 G. E. Thompson, T. Pennycook, and T. Hashimoto, 1814 81. Q. Gao, et al. Preparation of in-situ 5vol% TiB2 par- 1867 1815 Grain refining mechanism in the Al/Al-Ti-B system, ticulate reinforced Al-4.5 Cu alloy matrix composites 1868 – 1816 Acta Mater. 84, 292 304 (2015). assisted by improved mechanical stirring process, 1869 67. M. K. Aghajanian, M. A. Rocazella, J. T. Burke, and – 1817 Mater. Des. 94,79 86 (2016). 1870 S. D. Keck, The fabrication of metal matrix compo- 82. G. R. Liu. A step-by-step method of rule-of-mixture 1818 sites by a pressureless infiltration technique. J. 1871 – of fiber-and particle-reinforced composite materials, 1819 Mater. Sci. 26(2), 447 454 (1991). Compos. Struct. 40, 313–322 (1997). 1872 1820 68. S. V. Prasad, and R. Asthana, Aluminium metal- 83. J. C. Halpin and J. L. Kardos. The Halpin-Tsai equa- 1873 1821 matrix composites for automotive applications: tribo- tions: a review. Polymer Eng. Sci. 16, 344–352 1874 logical considerations, Tribol. Lett. 17(3), 445–453 1822 (1976). 1875 (2004). 84. Z. Hashin and S. Shtrjkman, A variational approach 1823 69. S. Amirkhanlou and B. Niroumand, Development of 1876 to the theory of the elastic behaviour of multiphase 1824 Al356/SiC cast composites by injection of SiC con- 1877 p p materials. J. Mech. Phys. Solids. 11, 127–140 (1963). taining composite powders, Mater. Des. 32(4), 1825 85. L. Tuchinskii, Elastic constants of pseudoalloys with 1878 1895–1902 (2011). 1826 a skeletal structure, Powder Metall. Met. Ceram. 22, 1879 70. S. Amirkhanlou and B. Niroumand, Effects of 1827 588–595 (1983). 1880 reinforcement distribution on low and high tempera- 91. H. Peng, A review of consolidation effects on tensile 1828 ture tensile properties of Al356/SiC cast composites 1881 p properties of an elemental Al matrix composite. 1829 produced by a novel reinforcement dispersion tech- 1882 Mater. Sci. Eng. A. 396,1–2 (2005). 1830 nique. Materi. Sci. Eng. A. 528(24), 7186–7195 1883 87. H. B. Michael Rajan, S. Ramabalan, I. Dinaharan, 1831 (2011). 1884 and S. J. Vijay, Synthesis and characterization of in 1832 71. L. A. Jacobson and J. McKittrick, Rapid solidification 1885 – situ formed particulate reinforced 1833 processing, Mater. Sci. Eng. R. 11(8), 355 408 1886 (1994). AA7075 aluminum alloy cast composites, Mater. – 1834 72. M. Asta, C. Beckermann, and A. Karma, Des. 44, 438 445 (2013). 1887 1835 Solidification microstructures and solid-state paral- 88. Z. Liu, et al. Effect of ultrasonic vibration on micro- 1888 1836 lels: recent developments, future directions. Acta structural evolution of the reinforcements and 1889 1837 Mater. 57(4), 941–971 (2009). degassing of in situ TiB2p/Al-12Si-4Cu composites, J. 1890 Mater. Process. Technol. 212(2), 365–371 (2012). 1838 73. K. M. Sree Manu, S. Arun Kumar, T. P. D. Rajan, 1891 M. Riyas Mohammed, and B. C. Pai, Effect of alu- 89. J. Geng, et al. The solution treatment of in-situ sub- 1839 1892 mina nanoparticle on strengthening of Al-Si alloy micron TiB2/2024 Al composite, Mater. Des. 98, – 1840 through dendrite refinement, interfacial bonding and 186 193 (2016). 1893 1841 dislocation bowing, J. Alloys Comp. 712, 394–405 90. T. Hong, Y. Shen, J. Geng, et al. Effect of cryogenic 1894 1842 (2017). pre-treatment on aging behavior of in-situ TiB2/ 1895 – – – 1843 74. M. L. Ted Guo and C. Y. Tsao, Tribological behav- Al Cu Mg composites, Mater. Charac. 119,4046 1896 (2016). 1844 iour of aluminium/SiC/nickel-coated graphite hybrid 1897 composites. Mater. Sci. Eng. A. 333, 134–145 (2002). 91. K. Tee, L. Lu, and M. Lai, In situ stir cast Al-TiB2 1845 75. P. K. Rohatgi, K. Pasciak, C. S. Narendranath, et al. composite: processing and mechanical properties, 1898 1846 Evolution of microstructure and local thermal condi- Mater. Sci. Technol. 17(2), 201–206 (2001). 1899 1847 tions during directional solidification of A356-SiC 92. K. L. Tee, L. Lu, and M. Lai, In situ processing of 1900 1848 particle composites. J. Mater. Sci. 29(20), 5357–5366 Al-TiB2 composite by the stir-casting technique, J. 1901 – 1849 (1994). Mater. Process. Technol. 89, 513 519 (1999). 1902 93. K. Tee, L. Lu, and M. Lai, Synthesis of in situ Al- 1850 76. D. Zhao, F. R. Tuler, and D. J. Lloyd, Fracture at ele- 1903 vated temperatures in a particle reinforced compos- TiB2 composites using stir cast route, Compos. 1851 ite. Acta Metall. Mater. 42(7), 2525–2533 (1994). Struct. 47(1), 589–593 (1999). 1904 1852 77. Z. Asghar, G. Requena, and E. Boller, Three-dimen- 94. A. Changizi, A. Kalkanli, and N. Sevinc, Production 1905 1853 sional rigid multiphase networks providing high- of in situ aluminium–titanium diboride master alloy 1906 CRITICAL REVIEWS IN SOLID STATE AND MATERIALS SCIENCES 19

1907 formed by slag–metal reaction, J. Alloys Comp. 112. J. J. Moses, I. Dinaharan, and S. J. Sekhar, Prediction 1960 1908 509(2), 237–240 (2011). of influence of process parameters on tensile 1961 € 1909 95. L. Lu, et al. In situ TiB2 reinforced Al alloy compo- strength of AA6061/TiC aluminum matrix compo- 1962 – 1910 sites, Scripta Mater. 45(9), 1017 1023 (2001). sites produced using stir casting, Trans. Nonferrous 1963 Met. Soc. China. 26, 1498–1511 (2016). 1911 96. J. Mathew, et al. X-ray tomography studies on poros- 1964 ity and particle size distribution in cast in-situ Al- 113. Y. Liang, J. Zhou, and S. Dong, Microstructure and 1912 1965 Cu-TiB2 semi-solid forged composites, Mater. tensile properties of in situ TiCp/Al-4.5 wt.% Cu 1913 Charact. 118,57–64 (2016). composites obtained by direct reaction synthesis, 1966 1914 97. A. Mandal, M. Chakraborty, and B. Murty, Ageing Mater. Sci. Eng. A. 527(29), 7955–7960 (2010). 1967 1915 behaviour of A356 alloy reinforced with in-situ 114. Z. Liu, et al. Synthesis of submicrometer-sized TiC 1968 particles in aluminium melt at low melting tempera- 1916 formed TiB2 particles, Mater. Sci. Eng. A. 489(1), 1969 – ture, J. Mater. Res. 29(7), 896–901 (2014). 1917 220 226 (2008). 1970 98. C. Feng and L. Froyen, Microstructures of in situ Al/ 115. P. Li, E. Kandalova, and V. Nikitin, In situ synthesis 1918 1971 TiB MMCs prepared by a casting route, J. Mater. of Al-TiC in aluminium melt, Mater. Lett. 59(19), 2 – 1919 Sci. 35(4), 837–850 (2000). 2545 2548 (2005). 1972 1920 99. X. H. Chen and H. Yan, Solid–liquid interface 117. R. Tyagi, Synthesis and tribological characterization 1973 1921 dynamics during solidification of Al 7075-Al O of in situ cast Al-TiC composites, Wear. 259(1), 1974 2 3np – 1922 based metal matrix composites, Mater. Des. 94, 569 576 (2005). 1975 – 116. B. Yang, G. Chen, and J. Zhang, Effect of Ti/C addi- 1923 148 158 (2016). 1976 100. Z. Chen, et al. Development of TiB reinforced alu- tions on the formation of Al3Ti of in situ TiC/Al 1924 2 – 1977 minium foundry alloy based in situ composites – composites, Mater. Des. 22(8), 645 650 (2001). 1925 Part I: an improved halide salt route to fabricate Al- 118. N. Samer, et al. Microstructure and mechanical 1978 properties of an Al-TiC metal matrix composite 1926 5wt% TiB2 master composite, Mater. Sci. Eng. A. 1979 1927 605, 301–309 (2014). obtained by reactive synthesis, Compos. Part A. 72, 1980 50–57 (2015). 1928 101. A. Mandal, B. Murty, and M. Chakraborty, Sliding 1981 wear behaviour of T6 treated A356-TiB in-situ com- 119. S. Mohapatra, et al. Fabrication of Al-TiC compo- 1929 2 sites by hot consolidation technique: its microstruc- 1982 posites, Wear. 266(7), 865–872 (2009). 1930 ture and mechanical properties, J. Mater. Res. 1983 103. S. Amirkhanlou, S. Ji, Y. Zhang, et al. High modulus Technol. 5(2), 117–122 (2016). 1931 Al-Si-Mg-Cu/Mg Si-TiB hybrid nanocomposite: 1984 2 2 121. A. P. Amosov, A. Luts, and A. Ermoshkin, 1932 microstructural characteristics and micromechanics- 1985 Nanostructured aluminium matrix composites of Al- 1933 based analysis, J. Alloy Compd. 694, 313–324 (2017). 1986 10% TiC obtained in situ by the SHS method in the 106. A. Westwood, Materials for advanced studies and 1934 melt, Key Eng. Mater. 684, 281–286 (2016). 1987 devices. Metall. Trans. A. 19(4), 749–758 (1988). 1935 122. Z. Hashin and S. Shtrikman, A variational approach 1988 107. G. Li, M. Zheng, and G. Chen, Mechanism and kinetic 1936 to the elastic behaviour of multiphase materials, J. 1989 model of in-situ TiB /7055Al nanocomposites synthe- 1937 2 Mech. Phys. Solid. 11, 127–140 (1962). 1990 sized under high intensity ultrasonic field, J. Wuhan 123. X. Tong and H. Fang, Al-TiC composites in situ- 1938 Uni. Technol. Mater. Sci. Ed. 26(5), 920–925 (2011). 1991 1939 processed by ingot metallurgy and rapid solidifica- 1992 102. S. Kumar, et al. Tensile and wear behaviour of in tion technology: Part II. Mechanical behaviour, 1940 situ Al-7Si/TiB2 particulate composites, Wear. 29 – 1993 – Metall. Mater. Trans. A. (3), 893 902 (1998). 1941 265(1), 134 142 (2008). 120. A. Kumar, P. Jha, and M. Mahapatra, Abrasive wear 1994 1942 108. G. Han, et al. High-temperature mechanical proper- behaviour of in Situ TiC reinforced with Al-4.5% Cu 1995 1943 ties and fracture mechanisms of Al-Si piston alloy matrix, J. Mater. Eng. Perform. 23(3), 743–752 (2014). 1996 reinforced with in situ TiB2 particles, Mater. Sci. 124. S. Amirkhanlou and B. Niroumand, Synthesis and 1944 – 1997 Eng. A. 633, 161 168 (2015). characterization of 356-SiCp composites by stir cast- 1945 1998 104. S. Kumar, V. S. Sarma, and B. Murty, Effect of tem- ing and compocasting methods, Trans. Nonferrous 1946 perature on the wear behaviour of Al-7Si-TiB2 in- Met. Soc. China. 20, s788–s793 (2010). 1999 1947 situ composites, Metall. Mater. Trans. A. 40(1), 125. S. Amirkhanlou, R. Jamaati, B. Niroumand, and 2000 1948 223–231 (2009). M. R. Toroghinejad, Using ARB process as a solu- 2001 105. M. Wang, et al. Mechanical properties of in-situ 1949 tion for dilemma of Si and SiCp distribution in cast 2002 TiB /A356 composites, Mater. Sci. Eng. A. 590, – 1950 2 Al Si/SiCp composites, J. Mater. Process. Technol. 2003 246–254 (2014). 211, 1159–1165 (2011). 1951 109. R. Chang and L. J. Graham, Low-temperature elastic 126. J. C. Lee, J. Y. Byun, S. B. Park, et al. Prediction of 2004 1952 2005 properties of ZrC and TiC, J. Applied Phys. 37(10), Si contents to suppress the formation of Al4C3 in the – 1953 3778 3783 (1966). SiCp/Al composite, Acta Mater. 46(5), 1771–1780 2006 1954 110. W. Jiang, et al. Synthesis of TiC/Al composites in (1998). 2007 – 1955 liquid aluminium, Mater. Lett. 32(2), 63 65 (1997). 127. S. Amirkhanlou and B. Niroumand, Microstructure 2008 111. K. J. Lijay, et al. Microstructure and mechanical prop- 1956 and mechanical properties of Al356/SiCp cast com- 2009 erties characterization of AA6061/TiC aluminium posites fabricated by a novel technique, J. Mater. 1957 matrix composites synthesized by in situ reaction of Eng. Perform. 22(1), 85–93 (2012). 2010 1958 silicon carbide and potassium fluotitanate, Trans. 128. Z. Peng and L. Fuguo, Effects of particle clustering 2011 1959 Nonferrous Met. Soc. China. 26(7), 1791–1800 (2016). on the flow behaviour of SiC particle reinforced Al 2012 20 S. AMIRKHANLOU AND S. JI

2013 metal matrix composites, Rare Met. Mater. Eng. 146. N. Rengasamy, M. Rajkumar, and S. S. Kumaran, An 2066 2014 39(9), 1525–1531 (2010). analysis of mechanical properties and optimization 2067 2015 129. S. Balasivanandha Prabhu, L. Karunamoorthy, S. of EDM process parameters of Al 4032 alloy rein- 2068 2016 Kathiresan, et al. Influence of stirring speed and stir- forced with ZrB2 and TiB2 in-situ composites, J. 2069 ring time on distribution of particles in cast metal Alloy Compd. 662, 325–338 (2016). 2017 2070 matrix composite, Mater. Process. Technol. 171, 147. A. Mahamani, et al. Synthesis, quantitative elemental 2018 268–273 (2006). analysis, microstructure characteristics and micro hard- 2071 2019 130. S. Tzamtzis, N. S. Barekar, N. Hari Babu, et al. ness analysis of AA2219 aluminium alloy matrix com- 2072 2020 Processing of advanced Al/SiC particulate metal posite reinforced by in-situ TiB2 and sub-micron ZrB2 2073 2021 matrix composites under intensive shearing-A novel particles, Frontiers Auto Mech. Eng. 25,50–53 (2010). 2074 – 2022 Rheo-process, Compos. Part A. 40, 144 151 (2009). 143. S. Zhang, Y. Zhao, G. Chen, and X. Cheng, 2075 131. A. H. Properties, Selection: Nonferrous Alloys and Microstructures and dry sliding wear properties of in 2023 þ 2076 Special-purpose Materials, vol. 2, ASM International, situ (Al3Zr ZrB2)/Al composites, J. Mater. Process. 2024 Materials, Park, OH (1990). Technol. 184, 201–208 (2007). 2077 2025 132. B. A. Kumar and N. Murugan, Metallurgical and 148. I. Dinaharan and N. Murugan, Dry sliding wear 2078 2026 mechanical characterization of stir cast AA6061- behaviour of AA6061/ZrB2 in-situ composite, Trans. 2079 – – – 2027 T6 AlNp composite, Mater. Des. 40,52 58 (2012). Nonferrous Met. Soci. China. 22(4), 810 818 (2012). 2080 133. P. Yu, et al. In situ fabrication and mechanical prop- 149. G. N. Kumar, et al. Dry sliding wear behaviour of 2028 2081 erties of Al-AlN composite by hot extrusion of par- AA 6351-ZrB2 in situ composite at room tempera- 2029 tially nitrided AA6061 powder, J. Mater. Res. 26(14), ture, Mater. Des. 31(3), 1526–1532 (2010). 2082 2030 1719–1725 (2011). 150. J. D. R. Selvam and I. Dinaharan, In situ formation 2083 2031 134. C. Yang, et al. Microstructure and mechanical prop- of ZrB2 particulates and their influence on micro- 2084 2032 erties of AlN particles in situ reinforced Mg matrix structure and tensile behaviour of AA7075 alumin- 2085 – 2033 composites, Mater. Sci. Eng. A. 674, 158 163 (2016). ium matrix composites, Eng. Sci. Technol. Inter. J. 2086 135. Q. Hou, R. Mutharasan, and M. Koczak, Feasibility 20(1), 187–196 (2017). 2034 of aluminium nitride formation in aluminium alloys, 151. G. Gautam, et al. High temperature tensile and 2087 – þ 2035 Mater. Sci. Eng. A. 195, 121 129 (1995). tribological behaviour of hybrid (ZrB2 Al3Zr)/ 2088 2036 136. Q. Zheng and R. Reddy, Mechanism of in situ for- AA5052 in situ composite, Metall. Mater. Trans. A. 2089 2037 mation of AlN in Al melt using nitrogen gas, J. 47(9), 4709–4720 (2016). 2090 – 2038 Mater. Sci. 39(1), 141 149 (2004). 152. G. Gautam and A. Mohan, Effect of ZrB2 particles 2091 137. S. S. Kumari, U. Pillai, and B. Pai, Synthesis and on the microstructure and mechanical properties of 2039 þ 2092 characterization of in situ Al-AlN composite by hybrid (ZrB2 Al3Zr)/AA5052 in situ composites, J. 2040 nitrogen gas bubbling method, J. Alloy Compd. Alloy Compd. 649, 174–183 (2015). 2093 2041 509(5), 2503–2509 (2011). 153. K. Wang, et al. Fabrication of in situ AlN-/Al 2094 2042 138. Q. Zheng and R. G. Reddy, Kinetics of in-situ forma- inoculant and its refining efficiency and reinforcing 2095 2043 tion of AlN in Al alloy melts by bubbling ammonia effect on pure aluminium, J. Alloy Compd. 547,5–10 2096 – 2044 gas, Metall. Mater. Trans. B. 34(6), 793 804 (2003). (2013). 2097 139. M. Chedru, J. L. Chermant, and J. Vicens, Thermal 154. Y. Zhang, N. Ma, and H. Wang, Improvement of 2045 properties and Young’s modulus of Al-AlN compo- yield strength of LM24 alloy, Mater. Des. 54,14–17 2098 2046 sites, J. Mater. Sci. Lett. 20, 893–895 (2001). (2014). 2099 2047 140. M. Balog, P. Krizik, M. Yan, et al. SAP-like ultra- 155. S. Amirkhanlou, M. R. Rezaei, B. Niroumand, and 2100 2048 fine-grained Al composites dispersion strengthened M. R. Toroghinejad, High-strength and highly-uniform 2101 2049 with nanometric AlN, Mater. Sci. Eng. A. 588, composites produced by compocasting and cold rolling 2102 181–187 (2013). processes, Mater. Des. 32, 2085–2090 (2011). 2050 2103 141. I. Dinaharan, N. Murugan, and S. Parameswaran, 156. P. D. Lee and J. D. Hunt, Hydrogen porosity in dir- 2051 2104 Influence of in situ formed ZrB2 particles on micro- ectional solidified aluminium- alloys: in situ 2052 structure and mechanical properties of AA6061 observation, Acta Mater. 45(10), 4155–4169 (1997). 2105 2053 metal matrix composites, Mater. Sci. Eng. A. 157. M. K. Aghajanian, J. Burke, D. R. White, et al. A 2106 2054 528(18), 5733–5740 (2011). new infiltration process for the fabrication of metal 2107 – 2055 142. S. L. Zhang, et al. Fabrication and dry sliding wear matrix composites, SAMPE Quarterly. 20,4346 2108 behaviour of in situ Al-K ZrF -KBF composites (1989). 2056 2 6 4 2109 reinforced by Al3Zr and ZrB2 particles, J. Alloy 158. J. Chen, C. Hao, and J. Zhang, Fabrication of 3D- 2057 Compd. 450(1), 185–192 (2008). SiC network reinforced aluminium-matrix compo- 2110 2058 144. Y. Zhao, et al. Effects of molten temperature on the sites by pressureless infiltration, Mater. Lett. 60, 2111 – 2059 morphologies of in situ Al3Zr and ZrB2 particles and 2489 2492 (2006). 2112 þ 2060 wear properties of (Al3Zr ZrB2)/Al composites, 159. G. S. Daehn, B. Starck, and L. Xu, Elastic and plastic 2113 Mater. Sci. Eng. A. 457(1), 156–161 (2007). behaviour of a co-continuous alumina/aluminium 2061 2114 145. D. Zhao, et al. In-situ preparation of Al matrix com- composite, Acta Mater. 44, 249–261 (1996). 2062 2115 posites reinforced by TiB2 particles and sub-micron 160. B. Basu and K. Balani. Advanced Structural – 2063 ZrB2, J. Mater. Sci. 40(16), 4365 4368 (2005). Ceramics. John Wiley & Sons (2011). 2116 2064 2117 2065 2118