Effects of Ni and Si additions on mechanical properties and serrated flow behavior in FeMoPCB bulk metallic glasses

Abstract

A novel ductile Fe56Ni20Mo4P11C4B4Si1 bulk metallic glass (BMG) with saturation magnetic flux density of 0.93 T, coercivity of 1.9 A/m and plastic strain of 7% was successfully synthesized in this work. Effects of Ni and Si additions on mechanical properties and serrated flow behavior of Fe-Mo-P-C-B BMGs were systematically investigated. It was found that the simultaneous additions of Ni and Si are effective to improve the plasticity of Fe76Mo4P12C4B4 BMG as indicated by the increase in the plastic strain from 1.7% to 7%. Serrated flow behavior is not observed in Fe76Mo4P12C4B4 BMG. However, the chaos state occurs in Fe56Ni20Mo4P12C4B4 BMG, and eventually the self-organized critical (SOC) behavior appears in Fe56Ni20Mo4P11C4B4Si1 BMG. The stable shear-band dynamics leads to the formation of multiple shear bands, resulting in a complex deformation process follow the SOC dynamics. The improved plasticity might result from an increased number of potential shear transition zone sites, and a stronger tendency of forming shear band interactions. This work provides a perspective from serrated flow behavior to understand plastic deformation mechanism in Fe-based BMGs with different plasticity.