2024铝合金微屈服行为

MICROYIELD BEHAVIOURS OF A 2024 ALUMINIUM ALLOY

以２０２４Ａｌ合金为对象，采用连续加载法，详细研究了在各种热处理状态下该材料的微屈服行为。研究结果表明，在其连续拉伸过程中存在弹性、微屈服及宏观屈服３个阶段；微屈服阶段的硬化率远高于初期宏观屈服阶段的硬化率，表明微屈服与宏观屈服的位错运动机制有差异。其微屈服阶段的σ—ε１／２ｐ曲线有两种不同类型：（ａ）直线型及（ｂ）转折型，其中（ａ）型符合经典的ＢｒｏｗｎＬｕｋｅｎｓ关系；而（ｂ）型则不符合ＢＬ关系，这与热处理造成的不同微结构有关。热处理对该材料的微屈服强度有很大影响，固溶强化、时效第二相沉淀强化及多次热循环的位错亚结构多边化均能明显提高该合金的微屈服强度。

Microyield behaviours of a 2024Al alloy under different heat treatment conditions were investigated. Results of the study showed that during continuous tension there were three stages in the material, i.e. elastic deformation, microyield deformation and macroyield deformation. The working hardening rate of microyielding was remarkably larger than that of the initial stage of the macroyielding, implying different mechanism of dislocation motion in the two stages. In microyielding scope two kinds of σ vs σ 1/2 p  relationships existed: (a) Linear relations conformed to the classical Brown Lukens equation; (b) Transition relation, which were dependent to the microstructure of materials. The microyield strength could be strongly influenced by heat treatment specification. Solution strengthening, age hardening, or relieving of residual micro stress and stable recovering structure of dislocation due to thermal cycling treatment were great of advantage for increase of the microyield strength.