(1. 中国科学院 金属研究所，沈阳 110016；
2. 沈阳大学 机械工程学院，沈阳 110044)
摘 要: 研究Ti-55钛合金板材在890~910 ℃、初始变形速率为4.4×10−4~1.76×10−3 s−1条件下的超塑性变形行为。结果表明：在900 ℃、初始应变速率为8.8×10−4 s−1变形条件下平均晶粒尺寸在4 μm左右细小等轴晶的Ti-55钛合金板材的伸长率可达1 300%，表现出良好的超塑性；在一定成形温度下其超塑伸长率随应变速率的增大呈先增加后降低的趋势，存在最佳应变速率8.8×10−4 s−1，高于或低于8.8×10−4 s−1，板材的超塑变形能力均有明显降低；在高应变速率下，Ti-55板材的最大伸长率向高温区移动；超塑性变形过程中晶粒呈相互聚合长大的现象，应变诱发组织粗化是超塑变形过程中组织粗化的主要因素。
关键字: Ti-55钛合金；超塑性；变形速率；变形温度；显微组织
（1. Institute of Metal Research, The Chinese Academy of Sciences, Shenyang 110016, China;
2. College of Mechanical Engineering, Shenyang University, Shenyang 110044, China）
Abstract:The superplastic tensile tests were performed at various temperatures (890−910 ℃) and initial strain rates (4.4×10−4−1.76×10−3 s−1). The results show that the fine-grained Ti-55 sheet, with an average grain size about 4 μm, exhibits excellent superplasticity. On the optimal superplastic condition of 900 ℃ and initial strain rate 8.8×10−4 s−1, a maximum elongation of 1 300% can be achieved. There exists an optimal strain rate of 8.8×10−4 s−1 for each test temperature to get the highest strain, and the superplastic elongation would be significantly reduced at strain rates higher or lower than the optimum strain rate. The temperature for the best superplasticity of Ti-55 sheet moves to higher temperatures at high strain rates. The influence of the deformation on microstructure is obviously. The strain induce grain growth is one of the most prominent characteristic during superplastic deformation.
Key words: Ti-55 titanium alloy; superplasticity; strain rate; deformation temperature; microstructure
