(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙 410083)
摘 要: 在475 ℃、初始应变速率为3×10-4~1×10-3 s-1的变形条件下对5A90铝锂合金试样进行拉伸，研究合金超塑变形的应变分布以及其对空洞演化的影响。结果表明：合金超塑变形是不均匀的，应变和空洞沿着拉伸方向呈梯度分布。应变量、空洞的尺寸与体积分数由肩部到断口逐渐增大。在不同的应变速率条件下，空洞的长大机制不同。在较高的应变速率(1×10-3 s-1)条件下，空洞以塑性控制长大为主。降低应变速率至8×10-4 s-1以下时，空洞以扩散长大机制为主。而在同一局部应变区域，横截面与纵截面空洞长大机制也不同，横截面空洞呈球状，为扩散控制的长大机制；纵截面空洞呈不规则状，且沿拉伸方向被拉长，为塑性控制的长大机制。
关键字: 5A90铝锂合金；超塑性；局部应变；空洞
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metals Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The local strain distribution during superplastic deformation of 5A90 Al-Li alloy and its effect on the evolution of cavity were studied through uniaxial tension at constant temperature of 475 ℃ and different initial strain rates of 3×10-4-1×10-3 s-1. The results demonstrate that the deformation of alloy is inhomogeneity, the strain and cavity remains non-uniform throughout the gauge. The strain, cavity size and volume fraction were found to increase from the shoulder section to the fracture tip. The cavity growth is different under different initial strain rates. In the case of high strain rate (1×10-3 s-1), the cavity growth is controlled by plastic deformation, and reducing the strain rate to 8×10-4 s-1, the cavity growth is controlled by diffusional process. And in the region with same local strain, the cavity growth mechanism in longitudinal section is different from transverse section. The transverse section with spherical is controlled by diffusional process cavity, while the same longitudinal section with elongated cavity is controlled by plastic deformation.
Key words: Al-Li 5A90 alloy; superplacticity; local strain; cavity
