Abstract: Isothermal compression tests at a temperature of 950—1 100 ℃ and strain rates ranging from 0.01 to 1 s-1 were performed on alumina-forming austenitic (AFA) alloy Fe-20Cr-30Ni-0.6Nb-2Al-Mo to reveal the hot deformation characteristics. The evolutions of microstructure and nucleation mechanisms of dynamic recrystallization (DRX) were analyzed combined with the technique of OM, EBSD and TEM. The regression method was adopted to determine the thermal deformation activation energy, apparent stress index, and to construct a thermal deformation constitutive model. The results show that the flow stress is strongly dependent on deformation temperature and strain rate, which increases with decreasing temperature and increasing strain rate. The DRX phenomenon occurred more easily at comparably higher deformation temperatures or lower strain rates. Based on the method for solving the inflection point via cubic polynomial fitting of lnθ-ε curves, the critical strain (εc) during DRX were precisely predicted. The nucleation mechanisms of DRX during thermal deformation mainly included the strain-induced grain boundary (GB) migration, grain fragmentation, and subgrain coalescence.
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2017, Vol. 31 
