Abstract
Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties.
Highlights
Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility
We demonstrate that the B2 phase effectively improves the plastic deformation capability of the B2-bulk metallic glass composites (BMGCs) under tension, and the plastic predeformation endows this B2 reinforced BMGC (B2-BMGC) with high strength and a large elastic strain limit by reversible B2«B19’ phase transformation
The average chemical compositions for the B2 phase and the amorphous metallic glasses (MGs) matrix are detected by energy-dispersive spectroscopy (EDS) to be Zr52.1Cu41.7Al3.9Nb2.3 and Zr50.7Cu42.2Al4.1Nb3.0, respectively
Summary
Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. By plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension These unique elastic mechanical properties are attributed to the reversible B2«B199 phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. Second phases are in-situ or ex-situ introduced to reinforce the MG matrices[9,10,11,12,13], such as dendrite-reinforced Zr- or Ti-based bulk metallic glass composites (BMGCs)[14,15,16,17,18] Though their toughness or ductility is significantly increased, the yield strength and the elastic strain limit of BMGCs are decreased dramatically in contrast to monolithic BMGs15,18,19. We demonstrate that the B2 phase effectively improves the plastic deformation capability of the B2-BMGC under tension, and the plastic predeformation endows this B2-BMGC with high strength and a large elastic strain limit by reversible B2«B19’ phase transformation
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