Superior Strength with Enhanced Fracture Resistance of Al-Mg-Sc Alloy Through Two-Step Cryo Cross Rolling

The evolution of microstructure and the preferred orientation during the two-step cross rolling at room (RT) and cryogenic temperatures (CTs) on Al-Mg-Sc alloy were investigated and compared with the unidirectional rolled Al-Mg-Sc alloy in this study. In addition, the effects of two-step cross rolling on tensile, forming and void coalescence behavior were analyzed. After the solution heat treatment, the two-step cross rolling was executed with an initial 25 pct reduction in the unidirectional path and the final 25 pct reduction in the transverse direction. The two-step cross-rolled (TSCR) Al-Mg-Sc alloy at CT showed a higher fraction of sub-micron grains. The TSCR Al-Mg-Sc alloy exhibited brass and copper and a strong S texture. The texture indices and in-plane anisotropy values indicated the highly anisotropic nature of the TSCR Al-Mg-Sc alloy. During tensile deformation, the TSCR Al-Mg-Sc alloy at CT exhibited a strength value of 423 MPa, whereas the TSCR Al-Mg-Sc alloy at RT revealed only 378 MPa. The TSCR Al-Mg-Sc alloy at CT exhibited inferior formability compared with the TSCR Al-Mg-Sc alloy at RT and the solution heat-treated base alloy. The formability of the TSCR Al-Mg-Sc alloy was evaluated through the combined forming and fracture limit diagram (CFFLD). The presence of higher Goss-oriented grains enhanced the fracture resistance of the TSCR Al-Mg-Sc alloy at CT. Furthermore, consistency was found between the evaluated void coalescence parameters and the CFFLD.