Strain-rate-dependent promotion and suppression of dynamic recrystallization by LPSO phases in GW92ZK alloy
Description
This dataset supports an investigation into the strain-rate-dependent dual role of long-period stacking ordered (LPSO) phases in dynamic recrystallization (DRX) during hot deformation of GW92ZK (Mg–9Gd–2Y–0.5Zn–0.5Zr, wt.%) magnesium alloy. The central hypothesis is that LPSO phases exert competing effects on DRX through local deformation-induced defect accumulation and microstructural constraints, with their relative contributions governed by strain rate. Hot compression experiments were conducted at 300, 400, 450, and 500 °C under strain rates ranging from 0.001 to 1 s⁻¹. The resulting deformation behavior and microstructural evolution were investigated using stress–strain analysis, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and geometric phase analysis (GPA). Quantitative analysis focused on LPSO fragmentation, kink deformation, local lattice rotation, dislocation-related deformation, grain boundary evolution, and recrystallized fractions. The results reveal a non-monotonic relationship between strain rate, LPSO deformation, and DRX. At 400 °C and 0.1 s⁻¹, the LPSO fragmentation index reaches its maximum value of 3.29, whereas the DRX fraction decreases to a minimum of 2.3%. This anomalous behavior demonstrates that pronounced local deformation and defect accumulation do not necessarily produce extensive recrystallization. Microstructural observations suggest that LPSO kinking and fragmentation promote localized strain accommodation and dislocation accumulation, creating favorable conditions for DRX nucleation in the adjacent α-Mg matrix. Conversely, continuous lamellar LPSO structures constrain dislocation rearrangement and recrystallization boundary migration, thereby suppressing local DRX development. These findings support a competitive mechanism involving defect storage, dynamic recovery, effective driving force, and grain boundary migration. The dataset provides experimental evidence for understanding the spatial and kinetic decoupling between defect accumulation and recrystallization evolution. It can support further investigations of LPSO-mediated plastic deformation, strain-rate-dependent microstructural evolution, and thermomechanical processing of rare-earth magnesium alloys.
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The experimental data were obtained from hot compression tests and multiscale microstructural characterization of GW92ZK (Mg–9Gd–2Y–0.5Zn–0.5Zr, wt.%) magnesium alloy. The as-cast alloy was homogenized at 520 °C for 12 h to establish a relatively uniform initial microstructure. Cylindrical specimens with dimensions of 8 mm in diameter and 12 mm in height were prepared for thermomechanical testing. Hot compression experiments were performed using a Gleeble-3500D thermomechanical simulator at temperatures of 300, 400, 450, and 500 °C and strain rates of 0.001, 0.01, 0.1, and 1 s⁻¹, covering 16 deformation conditions. Specimens were heated at 10 °C/s, held for 3 min at the target temperature, and compressed to a nominal true strain of 0.7. Graphite and molybdenum foils were used to minimize interfacial friction. Following deformation, the specimens were water-quenched to preserve the deformed microstructures. Load–displacement data were recorded and converted into true stress–strain curves. Work-hardening analysis and the Poliak–Jonas method were employed to estimate the critical conditions for dynamic recrystallization (DRX). Microstructural characterization was conducted using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). SEM images were used to evaluate the spatial distribution and morphology of long-period stacking ordered (LPSO) phases. Consistent image segmentation procedures were applied to quantify LPSO area fraction, aspect ratio, kink angle, and a relative fragmentation index based on the perimeter-to-area ratio. EBSD analysis was performed to characterize grain orientations, grain boundary misorientations, kernel average misorientation (KAM), grain reference orientation deviation (GROD), and recrystallized and substructured regions. Geometrically necessary dislocation (GND) distributions were estimated through crystallographic orientation-gradient analysis using MATLAB-based processing. TEM, scanning TEM, selected-area electron diffraction, and high-resolution TEM were employed to investigate LPSO kinking, dislocation structures, and local lattice distortions. Fast Fourier transform (FFT), inverse FFT, and geometric phase analysis (GPA) were used to characterize nanoscale lattice strain and rotation fields. For reproducibility, deformation conditions, specimen preparation procedures, image segmentation criteria, and crystallographic analysis methods were applied consistently across the investigated conditions. The resulting measurements were compared to establish relationships among LPSO deformation, defect accumulation, dynamic recovery, and DRX evolution under different strain rates.