热处理对Ti650钛合金电子束焊接组织和力学性能的影响

Effect of Heat Treatments on Microstructure and Property of Electron Beam Weldment of Ti650 Alloy

摘要:

对Ti650合金电子束焊接样品进行了不同制度的热处理，研究了焊后热处理工艺对合金焊接样品的组织和力学性能影响。结果表明，Ti650合金真空电子束焊缝焊后主要以亚稳马氏体α′相为主。经700℃/2hAC退火后，焊缝中马氏体α′相发生近平衡相变α′→α，同时焊缝中析出大量次生短针状α相。经1010℃/1.5hWC+650℃/2hAC处理后，α相发生了明显粗化和等轴化。次生析出的短针状α与原始粗化的α片层相结合有效的提高焊缝强度，阻碍了裂纹的扩展，使焊接接头在该条件下具有较好的强度和塑性。经固溶时效后再经700℃/2hAC处理，晶界处逐渐析出等轴α，弱化了晶界强度，引起其塑性的降低。综合分析焊缝区的组织和性能，Ti650合金焊接样品推荐采用1010℃/1.5hWC+650℃/2hAC进行焊后热处理，焊缝和基体的性能能够获得较好匹配。

Abstract:

The effects of post-weld heat treatment on the microstructure and mechanical properties of Ti650 alloy electron beam welding (EBW) samples were studied. The results indicated that metastable martensite α′ is the main phase in the fusion zone of welding seam. During 700℃/2hAC heat-treatment, a phase transition α′→α occurred, and a large number of short aciculate secondary α were precipitated in the fusion zone. After 1010℃/1.5hWC+650℃/2hAC heat treatment, α was obviously coarsened and equiaxed. The microstructure contains the original coarse layer and the secondary short acicular alpha can effectively improve the strength and prevent the crack growth of welded joint. The welded joint has better strength and plasticity under the condition. After subsequent treatment at 700℃/2hAC, some equiaxed alpha can be found gradually precipitated at the grain boundary, resulting in a decrease in strength and plasticity of the grain boundary. In conclusion, 1010℃/1.5hWC+650℃/2hAC is the most suitable post-welding heat treatment for Ti650 EBW welded joint to make the properties of weld and matrix be well matched.