Characterization of Microstructure Degradation and Quantitative Mapping Relationship with Fatigue Life for DD6 Alloy
Taking DD6 nickel-base single crystal superalloy as the research object,the degraded microstructure was obtained by simulating the service environment through high-temperature long-term or thermal coupled stress aging treatment.The degradation mechanism of the microstructure and corresponding residual fatigue life were studied,and an appropriate quantitative characterization method of the microstructure was explored to establish a mapping relationship between the degree of microstructure degradation and fatigue life.The results show that during service in the thermal environment,the γ'phase of DD6 alloy undergoes coarsening and rafting degradation,and the fatigue life under stress ratio of 0.1 at 980 ℃ is reduced.By using the dimension parameters of γ and γ'phase in the current state,a unified quantitative mapping relationship with high correlation coefficients can be established between the high-temperature coarsening or rafting microstructure of DD6 alloy and fatigue life.Moreover,this characterization method does not require obtaining the initial microstructure size,which is more meaningful for engineering applications.
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