TID-4500, UC-25 Metals, Ceramics, and Materials [3 LAWRENCE UVBRMORE LABORATORY UCRL-51269 FINAL REPORT OF THE LIGHT ARMOR MATERIALS PROGRAM R. L. Landingham A. W. Casey MS. date: September 15, 1972 -NOTICE- Thli report wu prepared as in account of work sponsored by the United States Government, Neither Ihe United Stit«s nor the United Stales Atomic Energy Commission, not any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or Implied, or assumes any legal liability or responsibility for the accuracy, com­ pleteness or usefulness of any Information, apparatus, product or process disclosed, of represents that Its use would not infringe privately owned rights. me —•"—tmrnimmtiun Foreword This report covers the work performed on the August 1970 extension of the Advanced Research Projects Agency (ARPA) order 980. This effort was directed to­ ward the development of light armor materials. The 'nltial concepts behind the development of these materials are described in previous LLL reports. 1-5 Contents Foreword jfi Abstract 1 Introduction 2 The Effect of Composition and Microstructure on Ballistic Performance of Be2B and Be4B 4 Hot-Pressed Targets 4 Hot-Pressing 4 Reaction Hot-Pressing 5 Grain Size g Fracture Mechanism 11 Process Variables 17 Cast Targets 22 Directional Solidification 23 Grain Nucleation ........... 24 The Ballistic Performance of Metal-Graded or Reinforced Beryllium Boride Armor 25 Be4B-Be 26 Be.B-Nl or Ni Based AUoy 29 Toxicity Studies 30 Environmental Tests 36 Summary 40 Acknowledgments 41 Appendix A. Preparation of Materials and Analytical Evaluation ... 42 Appendix B. Average Griin Size Determination 45 Appendix C. Evaluation of Fractured Surfaces with Electron Microscopic Techniques 46 Appendix D. The Collection and Characterization of Powders Generated by Ballistic Impact 47 References 49 -v- FINAL REPORT OF THE LIGHT ARMOR MATERIALS PROGRAM Abstract Beryllium boride compounds have been discussed. It has been shown that grain evaluated as potential materials for use in size can in some cases be controlled by light armor applications. Target speci­ process variables. Toxicity Investigations mens have been prepared by hot-pressing Have also been carried out. As a part of and casting techniques and subjected to these toxicity studies the amount and size ballistic testing. In each case, ballistic distribution of ballistic debris has been performance was found to be strongly determined. Environmental studies have related to composition and to the micro- shown the beryllium borides to be resistant structure of the target material. One to high temperature oxidation and thermal important microstructural feature has shock, but adversely affected by salt been found to be the grain size of the water. A working Be-B phase diagram is target material. The mechanism of also provided. The ballistic performance fracture is described and the relationship of beryllium borides was improved when they of the type of fracture to grain size were incorporated in m etal- graded targets. Introduction Studies conducted at these laborato- Several ceramics (i.e. B4C, AlgOg, SiC, ries 1-5 have led to a better understanding AIB12I possess the qualities of low density of penetration mechanics. Knowledge of and high incompressibility, but even at high the important material parameters that hydrostatic confining pressures, only a few operate during the penetration process low-density ceramics (BeO, BegB, Be4B, has uelped reveal the path to be taken in and MgO) show ductility. However, ductility the development of materials for use as can be incorporated in some ceramics by light armor. In general, the ideal mate­ addition of the proper metal to form a cermet. rial should exhibit the proper blanace An improvement in ballistic performance by between low density, high incompress- the addition of metal, and the existenceof an ibility (high yield strength and impedance) optimum in metal concentration have been and the ability to dissipate tensile previously demonstrated with the TiC-Ni- stresses without fracturing (ductility). Mo system. Unfortunately, no cermets A detailed evaluation of these material having both low density (<3.0 g/cc) and parameters has been previously high incompressibility have been hereto­ described.^.* fore developed. -1- Beryllium borldes have the above prop­ actually reduces the density of the ceramic. erties plus the capability of forming low Increasing the beryllium metal content density cermets. Indeed, combining leads to a more ductile cermet. The beryllium metal with beryllium borlde ductile behavior of beryllium has been Table 1. Ballistic limits for various ceramics bonded to 0.25-in. 6061-T6 aluminum. Density b d a V c A BL A2700 p°A2700 Ceramic (g/cc) (in.) (ft/sec) (in.) (g/cm2) *S B4C 2.50 0.290 2700 ± 50 0.29 1.84 1.00 BeO 2.84 0.250 2500 ± 50 0.27 1.95 0.94 BeO + B 2.50 0.250 2320 ± 80 0.29 1.84 1.00 Coors AD85 2.79 alumina 3.43 0.340 2850 ± 50 0.32 0.66 Coors AD999 alumina 3.96 0.250 2660 ± 80 0.25 2.51 0.73 WESG" 995 2.79 alumina 3.85 0.303 2870 ± 50 0.285 0.66 Diamonite alumina 3.72 0.340 3170 ± 50 0.29 2.74 0.67 Carborundum hot-pressed 3.92 0.250 2550 ± 50 0.26 2.59 0.71 alumina Sapphire 3.98 0.250 2470 ± 80 0.27 2.73 0.67 Si 2.33 0.250 1200 ± 50 0.56 3.31 0.56 SIC 3.09 0.250 2175 ±75 0.31 2.43 0.76 Si3N4 2.815 0.355 1450 ± 50 0.(56 4.72 0.39 Quartz Ite 2.58 0.250 1250 ±100 0.54 3.54 0.52 B 2.36 0.22tf 2100 ±80 0.29 1.74 1.06 A1B12 2.53 0.250 2250 ± 80 0.30 1.93 0.95 Be2B 2.03 0.250 2150 ± 50 0.31 1.60 1.15 T1B2 4.46 0.236 2270 ± 50 0.28 3.17 0.56 TiBe12 2.25 0.250 2250 ±100 0.30 1.74 1.06 Pure 0.27 TIC 4.88 0.25 2500 ± 80 3.25 0.55 TiC + (Ni.Mo) cermet 5.63 0.25 3050 ± 80 0.22 3.15 0.58 WC-(k-a) 15.24 0.25 3300 ± 200 0.20 7.7 0.24 A = ceramic thickness. VBL experimental ballistic limit. A2700 = extrapolated ceiimic thickness for V = 2700 ft/sec BmL > ceramic areal density. $ - B4C areal density/ceramic areal density. -2- demonstrated under hydrostatic confining Be-B armor for specific applications were pressures of 6 to 63 kb*r at relatively low considered unrealistic during early stages strain rates (3 X 10 sec ). In view of of the program. Evaluation studies were the above facts, we undertook to explore directed instead toward more general the possibility of using beryllium boride areas in the expectation that such results systems in light armor applications. would be useful in selecting ar.d designing Extensive evaluation of the promising specific applications in the future. The Be-B compounds (Be.B and Be.B) was general areas studied were the relation­ initiated after exceptionally high ballistic ship of composition and mlcrostructure performances4* had been obtained on to ballistic performance, the effect of many preliminary test specimens. Bal­ fabrication processes on mlcrostructure, listic performances of several materials the ballistic performance of metal-graded are compared in Table 1 and Figs. 1 and 2. or reinforced beryllium borlde armor, A detailed description of the Be-B system beryllium boride toxicity, and environmental is given in Appendix A. Efforts to prepare effects on beryllium borides. 4000 1 1 1 1 -1— 1 1 1 T 1 1 1 1 1 1 1 1 Ceramic—. jS~ 6061-T6 aluminum 3500 - >l LRt. .30-cal sharp S BeO projectile—•» S 3000 - — 0.25 in. _S^ > S > 2500 . Tifie12— limit u ' ^,"-"DAD-85 alumina : 2000 1 (alii "^ V ± 50 ft/sec s *<»' BL 1000 1 1 1 1 _L_ J 1_ _•_ i. _i .1 i I.I • 1 i 1.0 1.5 2.0 2.5 Ceramic areal density, p" A — g/cm c Fig. 1. Ballistic limit versus ceramic areal density for aluminum backed ceramic targets." -3- 1.4 Ceromic facing "^ Fiborgloss .30-cal (REPCO 1.3 APM2 woven projectile- roving) 8a48 with SI 1.2 h-6 + 1.1 Be ,B graded u 'i with Bo metal B4C l.o g 0.9- 0.8 VBL±50ft/sec 0.7 -L 1500 2000 2500 3000 Ballistic limit, Vg, — ft/sec Fig, 2. Ballistic limit of targets with various ceramic impact surfaces compared to targets with B4C impact surfaces.5 The Effect of Composition and Microstructure on Ballistic Performance of Be2B and Be4B HOT-PRESSED TARGETS temperatures (<H100°C) and pressures (S4500 psi) were sufficient to achieve fully Hot-pressing dense targets. Hot-pressing was the primary fabrica­ The Be B and Be„B powders were hot- tion process used in preparing Ba-B pressed into target disks (3 in. diam). samples for investigations into the effects The following experimental procedure of variations in composition and micro- was used in the fabrication of these disks: structure on ballistic performance. Hot- ti The powder was uniformly loaded into pressing allowed easy control of fabrica­ the lined (graphite paper) graphite die tion parameters since relatively low and cold pressed at ~1000 psi. -4- • The die was next heated to the desired peratures were required to achieve dense temperature under minimum pres­ f>98% of theoretical) disks if the BeO or sure (<500 psl). higher boride contaminates (Be2B, BeB2, • The desired pressure was applied at etc) exceeded -3 wt% in Be.B or Be2B.