Hot compression test was carried out at 1000℃ to investigate the dynamic recrystallization nucleation mechanism of a nickel-base superalloy. It was found that the bulging of original grain boundaries was inhibited by carbides and deformation twins at the boundaries. Recrystallized nuclei evolved from the subgrains of dislocation reconfiguration along original grain boundaries, and the growth of the potential nuclei was carried out by the coalescence of subgrains. The necklace structure of recrystallized grains along original grain boundaries was attributed to the strain gradient from grain boundary to grain interior.
Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformatio behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasad Gegel, Malas, Murty and Semiatin were compared, and the physical significance of parameters was analyzed Meanwhile, the processing maps with different instability criteria were obtained. It was shown that instabilit did not occur when average power dissipation rate was larger than 50% in the temperature range of 1020e1130 C, corresponding to the strain rate range of 5 10 4e3.2 10 3s 1. The domain is appropriate fo the processing deformation of superalloy GH4742.
