Ti650合金650 ℃热暴露组织与性能研究

Study on the Microstructure and Properties of Ti650 Titanium Alloy with Thermal Exposure at 650 °C

摘要:

对Ti650合金进行1005 ℃/1.5 h/AC+660 ℃/2.5 h/AC热处理，随后进行热暴露实验及室温拉伸实验，对其热稳定性进行研究。结果表明，热处理后合金的最高极限抗拉强度是细密的片层组织为其提供的，未有析出相的参与。100~200 h时，硅化物已稳定析出不再长大，α₂相随着热暴露时间的增长而析出长大，200 h时α₂相达到临界尺寸6 nm，对合金的强化效果最大。此时第二相阻碍位错运动增大合金的极限抗拉强度大于α_s相的片层变厚时合金减小的极限抗拉强度，导致了合金的极限抗拉强度上升。200~500 h时，合金中的α₂相继续长大，位错由切过第二相向绕过第二相转变（位错环的形成），合金的抗拉强度逐渐减小。

Abstract:

Ti650 alloy was heat treated at 1005 ℃/1.5 h/air cooling (AC)+660 ℃/2.5 h/AC, followed by thermal exposure test and room temperature tensile test to study its thermal stability. The results show that the highest ultimate tensile strength (UTS) of the alloy after heat treatment is provided by the fine lamellar structure without the participation of precipitated phase. When the thermal exposure time is 100–200 h, the silicide precipitates steadily and no longer grow, and the α₂ phase grows with the increase in thermal exposure time. At 200 h, the α₂ phase reaches the critical size of 6 nm, which has the greatest strengthening effect on the alloy. At this time, the UTS of the alloy, which is increased by the second phase obstructing the dislocation motion, is greater than that which decreases when the layer of α_s phase thickens, resulting in the increase in UTS of the alloy. From 200 h to 500 h, the α₂ phase in the alloy continues to grow, and the dislocation transitions from cutting through the secondary phase to bypassing the secondary phase (the formation of dislocation rings), and the UTS of the alloy gradually decreases.