Effect of Al/Ti Ratio on Hot Deformation Characteristics and Microstructure Evolution of 15Cr-30Ni-Fe Heat-Resistant Alloy

The hot deformation behavior, microstructure evolution and dynamic recrystallization mechanism of the newly designed 15Cr-30Ni-Fe heat-resistant alloy were studied. The flow curves of the alloy exhibit obvious dynamic recrystallization characteristics of a single stress peak, and the increase in Al/Ti ratio enhances the deformation resistance of the alloy during hot working. The constitutive equation corrected by strain compensation was established. The processing map of the alloy was constructed based on the dynamic material model, and the accuracy of the processing map was confirmed by checking the evolution of the microstructure. With the increase in Al/Ti ratio, the optimum hot working window of the alloys at a strain of 0.9 is broadened from 1050-1150 °C/0.01-0.1 s⁻¹ to 1015-1150 °C/0.01-0.57 s⁻¹. The strain-induced precipitation of nano-sized Laves phase, (Ti,Nb)C and γ'-Ni₃(Ti, Al, Nb) pinning the movement of dislocations and grain boundaries in the alloy with a high Al/Ti ratio hinders the growth of DRX grains. The dynamic recrystallization mechanism in 15Cr-30Ni-Fe heat-resistant alloy is mainly discontinuous dynamic recrystallization (DDRX) with grain boundary bulge, supplemented by continuous dynamic recrystallization (CDRX) with sub-grain nucleation.