MECHANICAL BEHAVIOR ENHANCEMENT of MAGNESIUM ALLOY AZ61 with MICRO-Sic PARTICLES
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MECHANICAL BEHAVIOR ENHANCEMENT OF MAGNESIUM ALLOY AZ61 WITH MICRO-SiC PARTICLES Song-Jeng Huang,1 Murugan Subramani1, Dawit Bogale Alemayehu 1, Tien-Hsi Lee2, *, Kou- Chen Liu3, 1Dept. of Mechanical Engineering, National Taiwan University of Science and Technology 2Dept. of Mechanical Engineering, National Central University 3Dept. of Electronics, Chang Gung University * corresponding author: [email protected] Abstract In the present work, the mechanical behavior of magnesium alloy AZ61 with the effect of different weight % (0, 1 and 2) of micro-silicon carbide particles (SiCp) reinforcement were fabricated by gravity casting method using the stirring process was investigated at room temperature. After homogenization (T4) heat treatment of the prepared all samples are characterized by optical microscope (OM), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), mechanical behavior. Microstructure observation results found that increasing micro-SiCp into the magnesium matrices, significantly decreasing the grain size of the metal matrix composites. In the presence of micro-SiCp have been assisted to enhance the hardness value of metal matrix composites (MMCs). In addition, micro SiCp ultimate tensile strength (UTS), yield tensile strength (YTS) and elongation of the MMCs increased. As is evident, that added 1% of micro SiCp notable increment in the UTS and YTS were 170.06 and 108.17 respectively and elongation were decreased in 4.47%. Furthermore, adding 1% of micro SiCp led to decrease the UTS, YTS and elongation were 166.64, 100.64 and 3.44 respectively. Because increasing micro SiCp content latter it may be attributed to the agglomeration of the MMCs. However, the maximum value of strength has been achieved to adding 1% of micro SiCp MMCs. Obtaining tensile test results from experimental process were compared with finite element method results. Finite element results were good agreement with the experimental results. Keywords: Mg alloy AZ61, silicon carbide particles, homogenization, mechanical behavior, finite element method 1-130 1. Introduction In the recent year’s magnesium alloys has great interest in lightweight materials, because of their high strength to weight ratio, high stiffness and low density. Density of magnesium is less than that of aluminum and steel. For this reason magnesium alloys are very attractive materials for load bearing components in automobile industry [1] Reinforcement for metal matrix composite have different stipulation in profile. which is found by processing, production and matrix system of the composite materials. The following stipulations are commonly applicable for reinforcement materials: low density, chemical compatibility, high compression and tensile strength, good process ability and economic efficiency [2]. Magnesium, Aluminum, Copper and Titanium are the mainly used matrix metals and Al2O3, SiO2 SiC, TiB2, WS2 and INT are the commonly used secondary phase ceramic reinforcement particles, whiskers and fibers. They have low density, high levels of strength, hardness, young's modulus and thermal stability. While during the particle reinforcement with the matrix material the grain boundaries and smooth the way for formation of a grain structure. This increase the mechanical properties such as young's modulus, ultimate strength, yield strength and also influence to improve the fatigue and creep properties of the composite materials at low temperatures. However, SiC particles are the most commonly chosen reinforcement particle for magnesium alloy, because of its superior properties, low cost and easily availability [3] . Huang et al. [4] investigated the magnesium alloy AZ61 with the reinforcement of different weight percentage (0, 0.5 and 1) of SiC powder with a particle size 4.5μm fabricated by stir casting method for MMCs tubes hot extrusion. Obvious grain size refinement discovered on both additions of reinforcement and extrusion process. However, the grain refinement effect is significant improvement on 0.2% yield strength and ultimate tensile strength of magnesium MMCs. Wang, X. J., et al. [5] processing the grain size of magnesium alloy metal matrix composites decreased with increasing SiC particle content and as well as enhance the ultimate tensile strength, yield strength and elastic modulus of the MMCs. Afshin and co- workers are fabricated pure magnesium and magnesium alloy AZ80 with reinforcement of nano SiC particles with different weight percent (1.5, 2.5 and 3.5) by stir casting method. They reported their fabricated magnesium matrix composite materials are significant improvement in hardness, ultimate tensile strength and yield tensile strength. Additionally, increase the nano SiC particle into the monolithic materials more than 2.5 % approximately 1-131 there is no effect on grain size. As compare pure Mg and AZ80 alloy can be seen adding nano SiC particle led to remarkable increase in ultimate tensile strength and yield strength on the AZ80 alloy [6]. Huang, S. J., & Ali, A. N. [7] investigated the solution and ageing heat treatment process used to improve the micro plastic deformation behavior of as cast AZ61/SiCp metal matrix composites by stir casting method. Gupta et al. [8], Manoj Kumar et al. [9] studied the use of magnesium / silicon carbide composite. Magnesium 9.8 and 26.3wt% of silicon carbide particles (25μm) synthesized by using of decomposition melting Deposition (DMD) technique. Tensile tests are taken from the room temperature showed when SiCp increased the hardness, elastic modulus (E) and 0.2% yield tensile strength (YTS) increased by 43.3%, 30.2% and 33.9% but grain size, Ultimate Tensile Strength (UTS) and elongation decreased by 40%, 2.8% and 600% respectively. Hardness improvement and ductility decline due to the Mg2Si phase is formed at the interface between Mg and SiCp. Han Lin, [10] investigated as cast and heat treated microstructure and mechanical properties of magnesium alloy with reinforcement of with and without minor Sc addition. Their study reported that increasing the Sc to the as cast could refine the grains and refine the Mg17Al12 phase also suppress the formation of the Mg17Al12 phase. As a result, mechanical properties such as UTS, 0.2%YTS and elongation% at room temperature for the Sc containing as cast magnesium alloy significantly improved. Bita Pourbahari and co-workers [11] are investigated the synergistic effect of Gd/Al ratio on the mechanical properties of as cast Mg-Al-Gd-Zn alloys by changing the chemical composition of AZ61 to GZ61. For precedential, the UTS and elongation to failure of Mg- 3Al-3Gd-1Zn alloys were significantly enhanced by 4% and 180% respectively. But the yield strength become decrease. Further increment in Gd in Gd/Al ratio, which led to decrease the UTS and elongation. Aatthisugan I et al. [12], Studied mechanical and wear behavior of magnesium alloy AZ91D with reinforcement of boron carbide (B4C) and graphite particle reinforced hybrid composites were fabricated by stir casting method. their results show that the graphite reinforced hybrid composite revealed a lower wear loss compared to pure AZ91D and AZ91D/B4C composite. Addition of both particle reinforcements into the AZ91D alloy remarkably enhance the wear resistance, hardness and ultimate tensile strength. Wang, Xiaojun, et al. [13], investigated the effect of SiC nano-particles on micro structural and mechanical strength of AZ31 magnesium alloy matrix composites during hot rolling. they revealed the test results SiC nano-particles impede the formation of slip bands, which are 1-132 much more prevalent in matrix alloy sheets. For the mechanical properties of the hot rolling leads to notable improvement on both of alloy sheets and nano-composite sheets. In this work Studying the reinforcement of SiCp effect on mechanical properties as a function of SiCp wt.% on the magnesium alloy AZ61. Analyzing the tensile deformation behavior of AZ61/SiCp metal matrix composites, with the characterization of their microstructures. Obtain results from experiments process were compare with finite element method analysis. The numerical and experimental can also be applied for other types of materials. 2. Experimental procedures and materials 2.1 Material and fabrication of composites The magnesium alloy AZ61 was matrix material with chemical composition of Al- 5.95, Zn-0.64, Mn-0.26, Fe-0.005, Si-0.009, Cu-0.0008, Ni-0.0007 and Mg balance and silicon carbide particles were used as reinforcement. Particle size and weight percentage of silicon carbide particles shown in Table 1. In this study AZ61/SiCp magnesium matrix composites fabricate with different wt.% (0wt.%, 1wt.% & 2wt%) of silicon carbide particles by stir casting method. Table 1 Particle size and wt.% of SiCp in AZ61/SiCp Mg MMCs casts. Types of casting ingots Particle size of SiCp (μm) Wt.% of SiCp AZ61 ---- 0 AZ61/SiCp 10 1 AZ61/SiCp 10 2 During casting use fiber cotton to prevent heat loss and start with a temperature 100˚C and by waiting for about 10-15 minutes then increase the temperature 100˚C step up to 400˚C. At 400˚C SF6/CO2 gas allow inside the crucible to prevent burning of magnesium alloy AZ61. And then increase the temperature at 700˚C argon gas was applied to prevent oxidation. after the temperature was reach at 700˚C the AZ61/SiCp melt was stirred with two stir blade at 300 RPM and 3 min respectively. 1-133 Fig. 1. Final casting ingots (a) pure AZ61, (b) AZ61/1% of SiCp, (c) AZ61/2% of SiCp Finally the melt was poured into the mold, which placed inside the lower chamber of the furnace and then we get the final cast ingots. Fig. 1. shows that three types of ingots prepared by stir casting method. The preparation of ingots which, were made into specimen dimension of 15mm * 10 mm * 5 mm for microstructure and hardness test. Middle part of the ingot is used to make the specimen for tensile test specimens. All of the specimens are heat treated (homogenized) at 410˚C for 24 hrs. 2.2. Microstructure analysis Microstructure of cross section was observed by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS).