Dual mechanisms for plasticity enhancement in GH4169 alloy: Dynamic recrystallization and dislocation-absorbing subgrain networks

To elucidate the thermoplastic evolution mechanism of the GH4169 alloy during hot tensile deformation, hot-simulation tensile tests were conducted on a Gleeble-3800 simulator at temperatures ranging from 950 to 1050 °C, strain rates of 0.001-1 s -1 . The hot tensile behavior was investigated, and true stress-strain curves were established. The microstructural evolution was characterized using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and molecular dynamics (MD) simulations. The results showed that the elongation increased from 24% to 29% as the temperature rose from 950 °C to 1050 °C. This improvement was primarily attributed to the dislocation density difference across grain boundaries, which led to local boundary protrusion and facilitated the transformation of subgrains into dynamic recrystallized (DRX) grains with lower dislocation density. As the strain rate increased from 0.001 to 0.01 s -1 , the elongation decreased from 29% to 23%; in contrast, when the strain rate further increased from 0.1 to 1 s -1 , the elongation rose from 34% to 37%. This behavior can be attributed to the increase in the fraction of grains with Schmid factors above 0.45, which rises from 55.2% to 86.4%. In addition to the preferential activation of the optimal {111}<110> slip system, other slip systems were also activated, resulting in the formation of a networked subgrain structure bounded by dislocation walls. Accordingly, a novel mechanism was proposed in which the networked subgrain structure formed under high strain rates can absorb dislocations and redistribute stress and strain.