ニッケル基超合金中のγ析出物による析出強化機構の数値解析

概要

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Precipitation strengthening is one of the effective techniques to design highly strengthened alloys. Up till now, many researchers have attempted to develop a concept that describes the strengthening effect of precipitates, and however, that contains a lot of assumptions, such as that the shape of dislocation is straight and the width of dislocation core is ignored. Recently, 3-D atom probe experiments have found the formation of γ-precipitates in γ' phases in nickel-based superalloy. Also, tensile tests have revealed that the γ-precipitates have an influence on the precipitation strengthening. In this paper, the interaction between a spherical γ-precipitate and a super-dislocation, which is a pair of two perfect dislocations, is investigated using an atomistic-continuum hybrid method. The strengthening due to the γ-precipitates is decomposed into two different strengthening mechanisms, such as stacking-fault and coherency strengthening mechanisms. We successfully simulated the interaction between the dislocation and the γ-precipitate, and focused on the role of the flexibility of dislocation and the dislocation core in the strengthening mechanism. Finally we propose an equation for the coherency strengthening based on an idea of stacking fault width in the dislocation core. The equation provides an excellent evaluation of improvements of the material strength by the strengthening mechanism.
2009-05-25