(1. 北京工业大学 材料科学与工程学院，北京 100124；
2. 首都航天机械有限公司，北京 100076)
摘 要: 利用Gleeble-1500D热模拟试验机对板厚为4 mm的TA7 ELI材料在变形温度为800、850、900、950和1000 ℃，应变速率为0.01 s-1和0.001 s-1下进行高温拉伸实验，获得材料发生超塑性变形的温度区间和应变速率范围。采用炉中高温拉伸实验对Gleeble实验结果进行验证。得出在950~1000 ℃范围内，应变速率低于0.001 s-1时，TA7 ELI钛合金高温拉伸会出现超塑性变形。伸长率最高可达260%。在应变速率0.001 s-1、800 ℃时，TA7钛合金的断口组织中有动态再结晶现象。1000 ℃时，断口出现较为粗大的层片状α组织和明显的晶粒长大现象。m和n值都随着温度的升高而增大，在950 ℃时到达最大值。硬化现象能够有效的抑制颈缩，变形温度为950 ℃时，材料的硬化和软化达到较好的平衡，易获得较大的伸长率。
关键字: TA7钛合金；超塑性；高温拉伸；应变硬化指数；应变速率敏感性指数
（1. College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China;
2. Capital Aerospace Machinery Corporation Limited, Beijing 100076, China）
Abstract:The tensile tests of TA7 ELI alloy sheet with 4 mm thickness were performed by Gleeble-1500D machine at high temperatures and various strain rates. The temperature and strain rate ranges of superplastic deformation were obtained, which were verified by tensile test in furnace. In the range of 950-1000 ℃, the superplastic deformation of TA7 occurs when the strain rate is lower than 0.001 s-1. The elongation reaches 260%. At the strain rate of 0.001 s-1, dynamic recrystallization occurs at 800 ℃ while a lamellar-type coarse α phase and grain growth appear in the fracture at 1000 ℃. With the increase of temperature, the strain rate sensitivity exponent (m) and strain hardening exponent (n) both increase. The maximum values of m and n are obtained at 950 ℃ when the tension stiffening and high temperature softening behaviors of the material reach balance.
Key words: TA7 titanium alloy; superplastic; high temperature tension; strain hardening exponent; strain rate sensitivity exponent
