Research on hot deformation behavior and microstructure characterization of Mg-Nd-Zn-Zr magnesium alloy prepared by wire arc additive manufacturing

The study investigated the hot deformation behavior and microstructure evolution of a Mg-Nd-Zn-Zr alloy produced through wire arc additive manufacturing (WAAM). The microstructure of the initial deposited state samples showed a layered structure with alternating coarse and fine grains along the building direction. Hot deformation tests were conducted within the temperature range of 300–450 °C and the strain rate range of 0.001–1 s⁻¹, with a deformation of 50 %. A Strain-Compensated Arrhenius-Type (SCAT) model and hot processing maps were developed to forecast the optimal processing parameters for the WAAM Mg-Nd-Zn-Zr alloy. The results show that the rheological stress of WAAM Mg-Nd-Zn-Zr alloy is greater at low temperature and high strain rate, and smaller at high temperature and low strain rate. By examining the variations in power dissipation rate (η) alongside the evolution of dynamic recrystallization (DRX), the microscopic features of regions characterized by instability, low η, middle η, and high η were scrutinized. Rheological instability is mainly manifested in the unstable zone and the low η zone, with the lowest DRX score. Discontinuous dynamic recrystallization (DDRX) is the main softening mechanism, and Nd elements precipitate discontinuously. On the contrary, in the medium η and high η regions, Nd elements precipitate continuously, with uniform microstructure. Continuous dynamic recrystallization (CDRX) is the main softening mechanism.