Improved Plasticity of Fe25Co25Ni25(Si0.3B0.7)25 High Entropy Bulk Metallic Glass through the Addition of Cu

Abstract

This work was focused on enhancement in the plasticity of Fe 25 Co 25 Ni 25 (Si 0.3 B 0.7 ) 25 high entropy bulk metallic glass (HE-BMG) by adding minor Cu (0-1.2, in at.%). It is found that the appropriate addition of Cu can efficiently improve the plasticity of the present HE-BMG while the excessive addition of Cu will deteriorate again the plasticity, and especially, the plastic strain of the present HE-BMG is improved from 0.8% for the Cu-free alloy to 4.7% for the 0.3 at.% Cu-added alloy. The transmission electron microscopy observation shows that there are many α-Fe (Co, Ni) clusters with sizes of less than 5 nm dispersed in the glassy matrix in the 0.3 and 0.6 at.% Cu-added alloys, which may account for the significant improvement in the plasticity of the two alloys, and further increase in Cu content more than 0.9 at.% leads to the precipitation of α-Fe (Co, Ni) and Fe (Co, Ni) B compound grains with diameters of tens of nanometers, in which the plasticity of the present HE-BMGs has deteriorated rapidly.