Effect of T6 heat treatment on microstructure and mechanical property of 6101/A356 bimetal fabricated by squeeze casting

Abstract

6101/A356 bimetal was fabricated by squeeze casting technique and subsequent T6 heat treatment (heating at 540±3℃ for 5h, quenching in cold water and ageing at 175℃ for 4h). This research presents significant microstructure evolution and mechanical properties improvement of the metallurgical bonded 6101/A356 bimetal after T6 treatment. The transition zone between the A356 aluminum alloy and 6101 aluminum alloy is made up of fine equiaxed grain structure. After T6 heat treatment, the morphology of silicon particles in the A356 aluminum alloy changes from long, coarse plate-like to fine spherical, and Zn, Mg diffuse more homogeneously across the interface. The transition zone is broadened from ~110µm to ~170µm. Moreover, interfacial shear strength measured by push-out test is improved by about 34%, from 76.7MPa to 102.7MPa. In addition, micro-hardness for both the matrixes and transition region is increased simultaneously.