三重热处理对TC21钛合金网篮组织及拉伸性能的影响

Effect of triple heat treatment on basket-weave structure and tensile properties of TC21 titanium alloy

摘要:

对TC21钛合金进行三重热处理试验,研究了热处理温度和冷却速率对TC21钛合金网篮组织及拉伸性能的影响。结果表明,TC21合金在β单相区高温(990℃)固溶后,再经历两相区高温(870~910℃)时效和低温(590℃)时效后,合金的显微组织呈现典型的网篮组织。随着第二重热处理温度的上升,片状α相含量和长度显著降低,厚度增加,合金的强度增加,塑性下降。经不同的冷却速率处理后,水冷和空冷试样的显微组织均由α相、β相和马氏体α′组成,而炉冷试样仅由α相和β相组成。三者的拉伸性能相比较,水冷和空冷试样表现为强度较好,塑形较差；炉冷试样表现为塑形较好,强度较差。TC21合金较好的三重热处理工艺为：990 ℃/1 h AC+870℃/1 h AC+590℃/4 h AC。

关键词:TC21钛合金;三重热处理;网篮组织;拉伸性能;

Abstract:

The effect of heat treatment temperature and cooling rate on the basket-weave structure and tensile properties of TC21 titanium alloy is studied by triple heat treatment experiments. The results indicated that the microstructure of TC21 alloy presents a typical basket-weave structure, which is achieved by high temperature (990℃) solid solution in the β single-phase region, and then through high temperature(870~910℃)aging in the (α + β) phase region and low temperature (590℃) aging. With the increasing of the second heat treatment temperature, the content and length of the flake α phase decrease significantly, and the thickness of the flake α phase increases slightly, the strength of the alloy increases, the ductility decreases. After being treated with different cooling rates, the microstructure of TC21 titanium alloy consists of α phase, β phase and α′martensite in both water cooling and air cooling samples, but only α phase and β phase are identified in furnace cooled sample, Compared with the tensile properties of the three samples, the water cooling and air cooling samples showed better strength and poorer ductility, furnace cooling samples show good ductility and poor strength. The better triple heat treatment process for TC21 alloy is 990℃/1 h AC+870℃/1 h AC+590℃/4 h AC.

Key words:TC21 titanium alloy; triple heat treatment; basket-weave structure; Tensile properties