LC4铝合金在恒应变速率超塑性变形过程中的m-δ关系及组织演变

m-δRelationship and Structural Evolution During A Constant Strain-Rate Superplastic Deformation of LC4 Alloy

原始晶粒平均尺寸为8.7μm 的 LC4合金拉伸试样在515℃和6.7×10^(-3)min^(-1)恒应变速率条件下显示了良好的超塑性,所获得的延伸率达464%。在这种变形条件下,所测得的 m-δ关系曲线属于 m_L=m_(max)型,其最大 m 值为0.78,出现于δ=94%处。该 m-δ关系可表示为δ_I(%)=[C_I×0.0067(~mI^(-0.5)-1]×100在超塑性变形过程中有三种主要的组织演变发生,即扩散蠕变导致邻近晶界的无沉淀区的形成、晶粒的粗化、及空洞的产生。此合金超塑性变形的上述 m-δ关系曲线的形貌可根据超塑变形过程中发生的主要组织演变予以解释。

At 515℃,with a constant strain-rate of 6.7×10^(-3)min^(-1),tensile specimen of LC4 aluminum alloy with an initial average grain size of 8.7μm exhibi-ted good superplasticity.A fracture elongation of 464% was obtained.Under such a deformation condition,the m-δ relationship belongs to the m_L=m_(max)type,with a maximum m value of 0.78 at 94% strain.The m-δ relationship can be expressed as δ_1(%)=[C_1×0.0067^((m_1-0.5))-1]×100.During superplastic deformation,three kinds of structural evolution takes place,namely the formation of precipitate-free zones adjacent to grain boundaries due to diffusional creep,grain coarsening and cavity generation.The m-δ relatio-nship of superplasticity of the alloy mentioned above can be explained on the basis of the structural evolution during superplastic deformation.