Research on Abnormal Grain Growth of GH4080A Alloy during Heat-treatment after Double-pass Isothermal Compression

Under the condition of temperature 1000-1060 ℃ and strain rate of 0.1-10 s^-1, GH4080A alloy was subjected to a single and double pass thermal compression simulation test with the same total deformation amount. The thermal deformation behavior of the alloy in different passes was analyzed and calculated. The softening rate of sub-dynamic recrystallization under different thermal deformation parameters was founded to be related to the abnormal growth mechanism of heat-treated grains. The results show that the flow stress of GH4080A alloy decreases with the increase of deformation temperature and the decrease of strain rate during the single and double pass compression. The second pass compression stress is always slightly lower than the first pass stress. The increase of deformation temperature and strain rate lead to a higher softening rate of sub-dynamic recrystallization calculated through the variation of flow stress. The probability of abnormal growth of grains in the microstructure after heat treatment is almost constant with the softening rate of sub-dynamic recrystallization. When the softening rate of sub-dynamic recrystallization is high, there is a higher probability of abnormal grain growth in the microstructure of the alloy after heat treatment. This is mainly because the γ’ phase decreases in the microstructure during the deformation interval of the double pass thermal deformation.