Effects of tungsten fiber on failure mode of zr-based bulk metallic glassy composite
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etallic glasses (BMGs) have gained considerable attention as potential structural materials for engineering application in recent years. In comparison with crystalline metals or alloys, which have been extensively used in many areas, metallic glasses possess some exceptional mechanical properties—i.e., high tensile and compressive strength, good elasticity and excellent physical and chemical properties.[1,2] Recent studies have revealed some interesting mechanical properties of BMGs. Inoue et al. found that Co-based BMG has a very high fracture strength of over 5000 MPa.[3] Fracture toughness of some BMGs is much higher than that of brittle pffiffiffifficeramics and is generally in the range of 18 to 70 MPa m, which is comparable to that of polycrystalline metals or alloys.[4,5,6] BMGs are susceptible to fatigue degradation with fatigue exponent m of 1 ; 2 in the Paris power law relationship.[7,8,9] Among the several families of multicomponent metallic glasses, Zr-based metallic glasses have exhibited exceptional glass-forming ability with a low critical cooling rate and a wide supercooled liquid region.[10,11] Extensive studies have established that BMGs always fail with very little plasticity at room temperature under both tension and compression due to the formation of highly localized shear bands.[12,13] Therefore, many efforts have been devoted to improve the plasticity of BMGs while keeping high strength through processing BMG matrix composites.[14,15] Obviously improved mechanical properties have been obtained in a series of Zr- and Ti-based metallic glass H. ZHANG, Associate Professor, Z.F. ZHANG, Professor, Z.G. WANG, Professor, H.F. ZHANG, Professor, and Q.S. ZANG, Professor, are with the Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang, People’s Republic of China. Contact e-mail: [email protected] K.Q. QIU, Professor, is with the School of Materials Science and Engineering, Shenyang University of Technology, 110023 Shenyang, People’s Republic of China. Manuscript submitted May 13, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
matrix or ultra-fine-structured matrix composites.[16,17,18] Plastic strain as high as 30 pct and fracture stress of ;2 GPa have been observed in an in situ formed Ti-based composite containing ductile dendritic phase and nanostructured matrix synthesized by copper mold casting or arcmelting method.[14,18,19] The enhanced ductility has been shown to originate from the strong interactions of the shear bands in the glassy matrix with the dendritic phases.[19,20] Besides the dendrite-reinforced composites, tungsten fiber has been regarded as another reinforcement for BMG composite that exhibited enhanced mechanical properties under quasi-static or dynamic deformation.[21,22,23] Both compressive plastic strain to failure and fracture strength have been improved in such BMG composite.[21] Ballistic tests by firing tungsten fiber composite rods into aluminum and steel targets have indicated that shear deformation is the m
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