Flow Behavior and Dynamic Recrystallization Mechanism of 7050-T7451 Aluminum Alloy during Hot Deformation

The flow behavior, constitutive relationship, microstructure evolution and discontinuous yielding of 7050-T7451 alloy were investigated via isothermal compression tests. The results show that the flow curves exhibit extensive stress softening. The obvious discontinuous yielding was also observed at high strain rates. An enhanced strain-compensation Arrhenius model further compensating temperature, strain rate and strain was proposed, which is more suitable for describing the constitutive relationship of this alloy with high correlation coefficient and low mean square error. The Zener-Holloman (Z) parameter was utilized to characterize the combined influence of temperature and strain rate on dynamic softening mechanism. The alloy undergoes significant dynamic recovery under the conditions of high lnZ (>30), accompanied by slight geometric dynamic recrystallization. With the decrease of lnZ, the primary softening mechanism gradually transforms from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization. The stress softening is mainly related to CDRX, while the discontinuous yielding may be caused by the multiplication of dislocations.