Hot workability, microstructural evolution, and dual path DRX mechanism of the 70Cu–30Ni alloy

This work systematically investigates the hot deformation behavior of the 70Cu-30Ni alloy for marine engineering through hot compression tests. The microstructural evolution and dynamic recrystallization (DRX) mechanisms were thoroughly analyzed via electron backscatter diffraction and transmission electron microscopy. Based on the dynamic materials model (DMM), hot processing maps were constructed, and the optimal hot working parameters were determined to be 900–1050 °C and 0.00974–0.0879 s -1 . Microstructural analysis revealed that both the size and distribution of DRX grains are significantly affected by the deformation conditions. High temperatures promote grain growth and uniformity, while high strain rates increase the DRX fraction and broaden its spatial distribution. The DRX of the 70Cu-30Ni alloy follows dual-path synergistic mechanism, involving grain boundary-dominated discontinuous DRX (DDRX) and orientation gradient-induced DRX (OGI-DRX) occurring within grains. DDRX generates necklace-like new grains through bulging strain-induced grain boundary, however, it is inhibited at high temperatures and low strain rates. OGI-DRX triggers lattice rotation, promoting low-angle grain boundaries to evolve into discontinuous high-angle grain boundaries through dislocation absorption. New grains are formed via the DDRX and subsequently extend along the increasing orientation gradient through continuous DRX. The combined effect of these two DRX modes effectively refines the microstructure and enhances the hot workability of the alloy.