Microstructure and mechanical properties of friction stir welded joint of Zr55Cu30Al10Ni5 bulk metallic glass with pure copper

Zr55Cu30Al10Ni5 bulk metallic glass (BMG) plate and pure copper plates with 2 mm in thickness were successfully joined by friction stir butt welding. Microstructure characterization revealed that a clear interface between the two materials was formed in the stir zone and no crystallization from the amorphous phase can be detected. On the copper side in the stir zone, a transitional microstructure of refined elongated grain structure, refined equiaxial grain structure and coarse equiaxial grain structure was found varying with the distance from the BMG/Cu interface. The welded joint showed lower hardness than that of the base metals and finally fractured on the copper side in tensile tests. The ultimate tensile strength of the joint was about 253 MPa, which reached up to 95% of the pure copper.