钎焊热循环对GH4169合金组织与力学性能的影响OA

To delve into the impacts of multiple brazing thermal cycles at varying peak temperatures on the microstructure and properties of GH4169 alloy,this study conducted a comprehensive examination of how brazing thermal cycle processes influence the precipitates,grain size,tensile properties,and stress-rupture properties of the alloy.The findings reveal that as the thermal cycle temperature rises,the quantity of δ-phase precipitation diminishes,and its morphology undergoes a transformation from needle-like to rod-like and eventually to granular.Within the temperature range of 970-1010℃,the grain size experiences minimal alteration.However,when the temperature surpasses 1020℃,significant grain growth occurs.Both tensile strength and hardness initially ascend and then descend with an increase in the thermal cycle temperature,reaching their peak values at 1010℃.This phenomenon is mainly attributed to the dissolution of an appropriate amount of δ phase and the complete precipitation of γ″ and γ' strengthening phases at this temperature,while the grain size does not show significant coarsening.The room-temperature impact toughness demonstrates distinct trends across different thermal cycle ranges.In the 970-990℃range,it decreases with rising temperature due to the partial transformation of the δ-phase morphology from needle-like to rod-like.In the 990-1010℃range,it increases with temperature as the δ phase dissolves and the strengthening-phase-free zone vanishes.Nevertheless,a further increase in the thermal cycle temperature leads to a reduction in toughness because of grain growth.The stress-rupture life initially declines and then rises with an increase in the thermal cycle temperature,hitting its lowest point in the 990-1000℃range.This is caused by the partial transformation of the δ-phase morphology from needle-like to rod-like,which promotes microvoid nucleation and reduces the alloy's creep resistance.When the temperature further rises above 1020℃,the extensive precipitation of γ″ strengthening phases,along with significant grain growth,substantially enhances the alloy's creep performance.However,the substantial decrease in the needle-like δ-phase content results in increased notch sensitivity.Taking into account both mechanical properties and notch sensitivity,it is recommended to employ brazing thermal cycles around 1010℃to achieve a well-balanced combination of strength and stress-rupture performance.For service environments with higher notch sensitivity requirements,a thermal cycle temperature in the range of 970-980℃can be selected to minimize the risks of creep failure.