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

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 degrees C 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 degrees C. However, the volume fraction of particles decreased significantly when soaked for 5 min at 500 degrees C, and the coarse particles precipitated mainly at the grain boundaries. Hot deformation at the temperature of 500 C around and at the strain rate range of 0.1s(-1) was desirable for NZ30K alloy.