Flow instability criteria in processing map of superalloy GH79

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH79, 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 is shown that instability did not occur when average power dissipation rate was larger than 60% in the temperature range of 900–930 °C and 960–1080 °C, corresponding to the strain rate range of 5×10−4−1.8×10−1 s−1 and 5×10−4−1.5×10−1 s−1, respectively. The two domains are appropriate for the processing deformation of superalloy GH79.