A Comparative Study of Various Flow Instability Criteria in Processing Map of Superalloy GH4742

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation 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 instability did not occur when average power dissipation rate was larger than 50% in the temperature range of 1020-1130 °C, corresponding to the strain rate range of 5 × 10−4-3.2 × 10−3 s−1. The domain is appropriate for the processing deformation of superalloy GH4742.