激光焊接热输入对Ti_2AlNb合金组织性能的影响

Effect of Heat Input on the Microstructures and Mechanical Properties of Laser Welded Ti_2AlNb Alloys

研究激光焊接热输入对Ti．22A1．27Nb（at％）合金焊缝成形和力学性能的影响，利用OM、SEM、XRD和TEM等手段对焊接接头的显微组织特征进行了分析，并探讨了焊后热处理对焊接接头组织性能的影响。结果表明，连续激光焊接可以获得无缺陷、成形良好的焊接接头。焊缝区域组织主要为柱状的B2相，柱状晶的生长方向垂直于熔合线。焊缝和热影响区的显微硬度要高于母材，焊缝的平均显微硬度最高。随着热输入的增加，焊接接头的室温抗拉强度增加，但是焊接接头的延伸率较低。焊接接头650℃高温强度为母材的71％～75％，塑性则仅为母材塑性的40％左右。经过焊后热处理，焊缝由B2＋O相组成。O相增多使得焊缝的室温强度略有提高，且提高了650℃高温拉伸性能，高温抗拉强度最高可达母材的87．5％。

The effect of heat input on the appearance and and the microstructure evolution characterization of the mechanical properties of laser welded Ti-22AI-27Nb （at%） alloys was discussed, joints was investigated by means of OM, SEM, XRD and TEM. The effect of post-weld heat treatment on the microstructure and mechanical properties of welded joints was also discussed. The results show that a well-quality joint could be obtained using a continuous laser welding method. The fusion zone of the welded joint is composed of columnar B2 phase. The orientation of columnar grains is perpendicular to the boundary between the fusion zone and the heat affected zone. The microhardness of the FZ and HAZ are higher than that of the base metals, and the FZ exhibits the highest values in the welded joint. The tensile strength of the laser welded joints at room temperature increases as the heat input increases, but the elongation of the welded joint is low. The tensile strength of the welded joints at 650 ~C is 71%-75% of the base metal. However the elongation is only about 40% of the base metal. After post-weld heat treatment, the welded metal is composed of B2＋O phases. The average tensile strength of the welded joints at room temperature is tested to be about 928 MPa to 942 MPa. Post-weld heat treatment improves tensile properties at 650 ~C and the highest tensile strength of the joint achieves 87.5% of the base metal.