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

This work was focused on enhancement in the plasticity of Fe25Co25Ni25(Si0.3B0.7)(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 alpha-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 alpha-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.

Automated summary

This work focused on enhancing the plasticity of Fe25Co25Ni25(Si0.3B0.7)(25) high entropy bulk metallic glass (HE-BMG) by adding minor amounts of Cu. The appropriate addition of Cu significantly improved the plasticity, while excessive Cu addition had a negative effect. The observed alpha-Fe (Co, Ni) clusters in the alloys with 0.3 and 0.6 at.% Cu were responsible for the improved plasticity. However, the plasticity rapidly deteriorated when the Cu content exceeded 0.9 at.% due to the precipitation of alpha-Fe (Co, Ni) and Fe (Co, Ni) B compound grains.