时效处理对保留有Laves相的激光立体成形GH4169合金强化相析出与力学性能的影响OA

Granular Laves phase is beneficial for the mechanical properties of laser solid formed GH4169 superalloy.Nevertheless,the retention of Laves phase occupies a portion of the principal strengthening element Nb,influencing the precipitation and growth of γ"strengthening phase during subsequent aging process.Up to now,no research has been conducted to optimize the aging treatment process for the LSF GH4169 microstructure with reserved granular Laves phases.In this paper,two distinct short-time solution heat treatment processes were employed to obtain Laves phases with diverse characteristics,and an exploratory research on the optimization of aging process was carried out.The results indicated that the solution heat treatment temperature had a significant influence on the evolution of the grain and the Laves phase.After holding at 1020 ℃ for 30 min,coarse columnar grains and large-sized and irregular Laves phase particles still persisted in the microstructure.When the solution heat treatment temperature was elevated to 1050 ℃ and held for 30 min,the microstructure was mainly characterized by equiaxed grains and granular Laves phases.However,the variation of the Laves phase did not have a pronounced effect on the precipitation and growth of the γ"phase,and the γ"phases in the two solution heat treated microstructures had a similar coarsening rate.The room temperature tensile result demonstrated that the optimal aging treatment process for the LSF GH4169 microstructure with reserved Laves phase remained as follows:holding at 720 ℃ for 8 h,furnace cooling at 50 ℃/h to 620 ℃,holding for 8 hours,and finally air cooling.At this point,the yield strength,tensile strength,and elongation of the alloy were 1067.0 MPa±18.2 MPa,1240.3 MPa±21.0 MPa,and 11.4％±0.6％,respectively.The debonding of the granular Laves phase was the primary cause of the sample fracture.The high-temperature creep properties of the optimized microstructure under different stress conditions at 650 ℃ were further tested.With the increase in the applied stress,the creep life of the alloy gradually decreases.During the high-temperature creep process,dynamic recrystallization and grain growth phenomena occurred in the LSF GH4169 microstructure,and both processes were affected by the applied stress.A lower applied stress level resulted in a higher creep life,enabling the generation of more recrystallized grains and allowing for more time for growth.The creep fracture mechanism of the samples under different conditions was intergranular fracture.The findings deepen the understanding of the microstructure evolutions and creep behaviors of laser solid formed GH4169 alloy with granular Laves particles,which is conducive to promoting the application of additive manufacturing in the formation of key structural parts for aero engines.