<正> 我们对GH135合金的高温长期实验结果表明,存在一个“开裂界限”K_(It)(或称K_(Ihcc))。当应力强度因子K_I Creep crack growth of an Fe-Ni base alloy GH901 (similar to Incoloy901) was studied at 650--715℃ by electrical potential technique. The crack initiationand growth can be described by stress intensity K_I. When the initial stressintensity K_(Ii) was smaller than a threshold value K_(It), no crack growth was detectedin the testing time (200h). When K_(Ii) was larger than K_(It), the creep crack growthrate can be represented by an Arrhenius type equation. The activation energy forcreep crack growth was found in agreement with that for grain boundary diffusion.Fractography by SEM shows that the path of crack growth is along grain bound-aries. The physical origin of the threshold stress intensity K_(It) and the microscopicprocess of creep crack growth was explained in the light of grain boundary diffusionmechanism.
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