Effects of annealing on the interface microstructures and mechanical properties of hot roll bonded Ti6Al4V/AA6061 clad sheets

Abstract

In this study, Ti6Al4V/AA6061 clad sheets were successfully obtained via hot roll bonding. The effects of annealing on the interface microstructures and mechanical properties of the clad sheets were investigated. The interface microstructures were observed via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Tensile tests were conducted to investigate the mechanical properties of the clad sheets. The results demonstrated that the TiAl3 phase formed in the Ti/Al interface when the annealed temperature was above 550 °C. The Al atoms were the dominant diffusing atoms through the TiAl3 layer and reacted with Ti atoms at the Ti/TiAl3 interface. A thin layer including MgAl2O4 and unreacted Al was observed in the TiAl3 zone near the Al side. The thickness growth of the TiAl3 layer was dominated by linear growth. After annealing treatment, the tensile strength of the clad sheets initially decreased from the as-rolled to 400 °C annealed samples, subsequently increased with annealing temperature from 400−550 °C, and then finally decreased. The strength of the clad sheets was in good agreement with the calculated value from the rule of mixture. The ductility increased with increasing annealing temperature, reaching its maximum value at 550 °C, and then subsequently decreased at 600 °C.