提出了一种可以综合反映多组织因素对GH4738合金疲劳裂纹扩展速率影响的多组织因素交互影响方程, 并利用不同的热处理制度设计了具有不同组织特征的试样. 测定了经不同热处理制度后GH4738合金在650 ℃下的疲劳裂纹扩展速率. 利用该方程分析了GH4738合金晶粒尺寸、碳化物及γ′相尺寸对疲劳裂纹扩展速率的影响. 结果表明, 多组织因素交互影响方程能很好地定量描述各组织因素对GH4738合金疲劳裂纹扩展速率的影响及其综合影响. 增大晶粒尺寸、降低γ′相及碳化物尺寸均可降低GH4738合金疲劳裂纹扩展速率, 并且晶粒尺寸对GH4738合金的裂纹扩展速率的影响程度要高于γ′相尺寸及碳化物尺寸.
The effects of microstructure on the fatigue crack growth behavior of hard-to-deformed GH4738 superalloy have been studied by a number of researchers. However, most of these studies are confined to a single factor, such as the effect of grain size on the fatigue crack growth rate, and show the effect of single factor which do not reflect the combined impacts of multi-microstructure factors. Therefore, there is a need to develop a quantitative approach to predict the effects of multi-microstructure on fatigue crack growth behavior in the design of GH4738 alloy with high damage-tolerant microstructure. A new multi-microstructure factors interaction equation is proposed for the prediction of the effects of grain size, γ′ size and carbide size on fatigue crack growth rate of GH4738 alloy in this work. Different microstructures of GH4738 alloy are produced by different heat treatments (HT) for this equation. The fatigue crack growth experiments are carried out under constant stress ranges on compact tension (CT) specimens at 650 ℃ in air. Subsequently, the effects of grain size, γ′ size and grain boundary carbides size on the fatigue crack growth rate of GH4738 alloy are analyzed by using the interaction equation of multi-microstructure factors. The results show that the equation can well predict the fatigue crack growth rate of GH4738 alloy under different microstructures. The growth rate of fatigue crack in GH4738 can be decreased with increasing grain size and reducing γ′ size and carbide size. The effect of grain size on fatigue crack growth rate is more notice able than that of γ′ and carbide sizes.
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