(1. 北京工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，北京 100124；
2. 首都航天機(jī)械有限公司，北京 100076)
摘 要: 利用Gleeble-1500D熱模擬試驗(yàn)機(jī)對板厚為4 mm的TA7 ELI材料在變形溫度為800、850、900、950和1000 ℃，應(yīng)變速率為0.01 s-1和0.001 s-1下進(jìn)行高溫拉伸實(shí)驗(yàn)，獲得材料發(fā)生超塑性變形的溫度區(qū)間和應(yīng)變速率范圍。采用爐中高溫拉伸實(shí)驗(yàn)對Gleeble實(shí)驗(yàn)結(jié)果進(jìn)行驗(yàn)證。得出在950~1000 ℃范圍內(nèi)，應(yīng)變速率低于0.001 s-1時(shí)，TA7 ELI鈦合金高溫拉伸會(huì)出現(xiàn)超塑性變形。伸長率最高可達(dá)260%。在應(yīng)變速率0.001 s-1、800 ℃時(shí)，TA7鈦合金的斷口組織中有動(dòng)態(tài)再結(jié)晶現(xiàn)象。1000 ℃時(shí)，斷口出現(xiàn)較為粗大的層片狀α組織和明顯的晶粒長大現(xiàn)象。m和n值都隨著溫度的升高而增大，在950 ℃時(shí)到達(dá)最大值。硬化現(xiàn)象能夠有效的抑制頸縮，變形溫度為950 ℃時(shí)，材料的硬化和軟化達(dá)到較好的平衡，易獲得較大的伸長率。
關(guān)鍵字: TA7鈦合金；超塑性；高溫拉伸；應(yīng)變硬化指數(shù)；應(yīng)變速率敏感性指數(shù)
（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
