Effect of deformation parameters on dynamic recrystallization and γ′-phase of GH4742 superalloy
LI Zhen-tuan1,2, QIN He-yong1,2, TIAN Qiang1,2, ZHANG Wen-yun1,2, ZHAO Guang-pu1,2
1. High Temperature Materials Institute, Central Iron and Steel Research Institute, Beijing 100081, China; 2. GAONA Materials and Technology Company Limited by Shares, Beijing 100081, China
Abstract：In order to study the effects of deformation parameters on the dynamic recrystallization and γ′ phase of forged GH4742 superalloy,the true stress-true strain curves of forged GH4742 superalloy at deformation temperature of 1 050-1150 ℃ and the deformation ratio of 30%-70% under the strain rate of 0.1 s-1were obtained by single-pass isothermal compression experiments,the variation of true stress-true strain and peak stress under different deformation parameters was analyzed,and meanwhile the micro-substructure and γ′ phase were characterized during the dynamic recrystallization process under different deformation parameters by SEM and EBSD, the geometric dislocation density of the matrix and the proportion of dynamic recrystallization were quantitatively calculated,and the hardness of the matrix under different deformation parameters was measured. The nucleation mechanism of dynamic recrystallization under different deformation parameters was discussed,and the evolution of micro-substructure and γ′ phase was deeply analyzed during the dynamic recrystallization process. The results show that there were a large number of undissolved primary γ′ phase in the matrix at deformation temperature of 1 080 ℃,the proportion of low-angle grain boundaries(LAGs) exceeded 35%,and the proportion of dynamic recrystallization was less than 35%,and the nucleation mechanism was mainly continuous dynamic recrystallization; The size of the primary γ′ phase decreased,and then it re-dissolved progressively in the matrix at deformation temperature of 1 110 ℃,the proportion of LAGs was less than 8%,and the proportion of dynamic recrystallization was more than 75%,and the main nucleation mechanism was discontinuous dynamic recrystallization. With increasing deformation ratio,the size of primary γ′ phase increased and the number density of that decreased,the proportion of LAGs decreased significantly,and the proportion of dynamic recrystallization of the matrix increased. The hardness of the matrix increased significantly with the increase of the deformation ratio at the low deformation temperature,whereas the hardness increased first and then gradually tend to remain unchanged at the high deformation temperature. The dynamic recrystallization of GH4742 alloy had been completed at the deformation temperature of 1 110 ℃ and the deformation ratio of 50%,the microstructure was equiaxed dynamic recrystallized grains,and the matrix hardness was 357HV,which had a good hot forming performance.
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2022, Vol. 57 
