Dynamic Strain Aging Behavior of an Extruded Mg-3Gd-1Zn Alloy Under Compressive Deformation

The dynamic strain aging (DSA) behavior of an extruded Mg–3Gd–1Zn (wt.%) alloy was investigated under compressive deformation at intermediate temperatures (150–250 °C) and strain rates ranging from 5 × 10−5 to 10−3 s−1. The as-extruded alloy exhibited equiaxed grains (~20 µm), with all alloying elements retained in solid solution and a weak basal texture. Serrated flow was observed under different temperature and strain-rate conditions. The critical strain, which denotes the onset of serrations, decreased with increasing temperature and increased with strain rate. Notably, the temperature dependence of the critical strain exhibited anomalous non-linear behavior, with a sharp increase at 250 °C, attributed to the formation of low-mobility Gd–Zn clusters/precipitates that depleted mobile solutes from the matrix. In situ synchrotron radiation diffraction revealed the activation of {10.2}⟨10.1⟩ tensile twinning as the dominant deformation mechanism, with periodic plateaus in twin intensity coinciding with macroscopic stress serrations. HAADF-STEM analysis confirmed Gd and/or Zn segregation at twin boundaries and dislocations, leading to the formation of nanoscale clusters during deformation. The overall mechanical response is rationalized by a temperature-dependent competition between solute diffusion and solute clustering at elevated temperatures.