Stress Relaxation in Superalloys Due to Microstructural Changes
Tóm tắt
Relaxation of residual stresses in metallic materials is caused by diffusion of inhomogeneously distributed solved alloying elements and by microstructural mechanisms like rearrangements of dislocation structure and precipitation processes, respectively. Both processes are often linked with each other. Therefore, the description and the modelling of stress relaxation on a microstructural basis is very complicated. The aim of this study was to demonstrate some models for stress relaxation in metallic materials. The paper presents the relaxation of tensile loading stresses in Ni-based and Co-based superalloys at high temperatures. In stress relaxation tests the microstructure development was connected with a rearrangement of the dislocation structures and by a decreasing dislocation density. The stress relaxation in carbide strengthened superalloys is a typical case of dislocation relaxation in the presence of precipitations. By including the determined microstructure parameters, the effective stress model and also a constitutive model yields to qualitatively correct predictions of the tensile and relaxation behaviour.
Tài liệu tham khảo
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