Hot Deformation Behavior and Microstructural Evolution of Mg-Nd-Zn-Zr Magnesium Alloy

摘要

The hot deformation behaviors and microstructural evolution of Mg-3.0Nd-0.2Zn-0.4Zr (wt. %, NZ30K) alloy were investigated by means of the isothermal hot compression tests at temperatures of 350-500℃ with strain rates of 0.001, 0.01, 0.1 and 1s~(-1). The results showed that the flow stress increased to a peak and then decreased which showed a dynamic flow softening. The flow stress behavior was described by the hyperbolic sine constitutive equation with an average activation energy of 193.8 kJ/mol. The average size of dynamically recrystallized grains of hot deformed NZ30K alloy was reduced by increasing the strain rate and/or decreasing the deformation temperature. A large amount of fine particles precipitated in the grains interior and at the grain boundaries when heated to the compression temperatures and soaked for 5min below 450 ℃. However, the volume fraction of particles decreased significantly when soaked for 5 min at 500 ℃, and the coarse particles precipitated mainly at the grain boundaries. Hot deformation at the temperature of 500 ℃ around and at the strain rate range of 0. 1s~(-1) was desirable for NZ30K alloy.