(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083；
2. 中南大學(xué) 有色金屬材料科學(xué)與工程教育部重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083)
摘 要: 在475 ℃、初始應(yīng)變速率為3×10-4~1×10-3 s-1的變形條件下對(duì)5A90鋁鋰合金試樣進(jìn)行拉伸，研究合金超塑變形的應(yīng)變分布以及其對(duì)空洞演化的影響。結(jié)果表明：合金超塑變形是不均勻的，應(yīng)變和空洞沿著拉伸方向呈梯度分布。應(yīng)變量、空洞的尺寸與體積分?jǐn)?shù)由肩部到斷口逐漸增大。在不同的應(yīng)變速率條件下，空洞的長(zhǎng)大機(jī)制不同。在較高的應(yīng)變速率(1×10-3 s-1)條件下，空洞以塑性控制長(zhǎng)大為主。降低應(yīng)變速率至8×10-4 s-1以下時(shí)，空洞以擴(kuò)散長(zhǎng)大機(jī)制為主。而在同一局部應(yīng)變區(qū)域，橫截面與縱截面空洞長(zhǎng)大機(jī)制也不同，橫截面空洞呈球狀，為擴(kuò)散控制的長(zhǎng)大機(jī)制；縱截面空洞呈不規(guī)則狀，且沿拉伸方向被拉長(zhǎng)，為塑性控制的長(zhǎng)大機(jī)制。
關(guān)鍵字: 5A90鋁鋰合金；超塑性；局部應(yīng)變；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
