Balancing benefits of strength, plasticity and glass-forming ability in Co-based metallic glasses

Development of advanced metals materials with ultrahigh strength, large plasticity and high thermostability is one of the most attractive aims for materials researchers. Co-based bulk metallic glasses (BMGs) with the highest strength (up to 6 GPa) and special strength (up to 650 Nm/g) among all of metals materials so far we known have received extensive attentions. In this paper, a family of Co-Ta-B-Si BMGs with high glass-transition temperature (above 870 K), large compressive plasticity (up to 6.4 %) and high strength (above 5.5 GPa), and high glass-forming ability (the critical diameter, D_c: up to 4 mm) was developed by accurately tuning metalloid element contents of Si and B in the parental alloy of Co₅₅Ta₁₀B₃₅. The changes of glass formation and plasticity caused by the adjustment of the constituent metalloid elements were evaluated by the combination of experimental and calculated results. The reason for the significant improvement of plastic deformation is revealed by the analysis of the self-organization behaviors of high-density shear bands.