夹杂物尺寸对粉末高温合金低周疲劳寿命影响的机制

为了研究夹杂物尺寸对粉末高温合金低周疲劳寿命的影响，将夹杂分别位于试样中心、表面、亚表面并改变其尺寸，研究同一位置下，不同夹杂物尺寸对应力应变分布的影响，结果表明:当夹杂物界面上不含微孔洞时，夹杂物与基体尺寸比例在实验室尺度（1:25）到工程尺度（1:10 000）范围内，夹杂物尺寸对应力应变影响很小；工程实际中，缺陷往往会与基体形成不完好的连接界面，即初始损伤破坏——微孔洞。缺陷对寿命的影响原因:夹杂物尺寸越大，它与基体的界面就越大，出现不完好连接和缺陷的概率就会增加，容易在界面处产生初始损伤破坏；当夹杂物界面上含有微孔洞时，随着夹杂物尺寸变大，界面正应力明显增大，界面切应力微弱减小，基体最大正应力和最大塑性应变均明显增大。

Influence Mechanism of Inclusion Size on Low Cycle Fatigue of Powder Metallurgy Superalloy

To study the effect of inclusion size on the low cycle fatigue life of powder metallurgy superalloy, the stress distributions at the same locations (center, subsurface and surface) were analyzed by finite element simulation. The calculation results show that when the inclusion/matrix interface does not contain the microhole, and the inclusion and matrix size proportion in a laboratory scale (1:25) to the project scale (1:10 000), the inclusion effect on stress and strain is very small. The influence of defects on the fatigue life is mainly due to the larger the inclusion size, the greater the interface between the substrate and the matrix is, the probability of imperfect connections and defects will increase, which will lead to initial damage at the interface.When the inclusion/matrix interface containing microholes, as the inclusion size bigger, interface normal stress increases obviously, interface shear stress decreases weakly, and the matrix maximμm normal stress and maximμm plastic strain are significantly increased. The influence mechanism of inclusion size on low cycle fatigue property should be that the interface of inclusion/matrix often contains microholes.