在线去应力退火对线性摩擦焊TiAl合金接头微结构与力学性能的影响机制

Microstructure Evolution and Mechanical Properties of Linear Friction Welded TiAl Alloy Joint with Online Stress Relieving

摘要:

采用在线去应力退火工艺对线性摩擦焊TiAl合金接头进行处理，避免了焊后裂纹的产生。显微组织分析表明，接头焊缝区与热力影响区界限明显，焊缝区主要由等轴γ晶组成，并含有少量的α₂相。靠近焊缝的热影响区内的层状γ晶具有明显的流线特征，其方向与焊接界面热塑性金属的流动方向一致。接头的显微硬度从母材区到焊缝区呈逐渐增加的趋势，焊缝区显微硬度相较于母材区增加了约1700 MPa；接头的室温抗拉强度与母材相当，在683 MPa到717 MPa之间。焊缝区的细晶强化效应是接头强度较高的主要原因。

Abstract:

Crack-free TiAl joints were welded by linear friction welding with online stress relieving process. Microstructural examination demonstrates that the joint has a clearly identified weld zone which consists mainly of equiaxed γ grains with a few α₂ phase. Lamellar grains in thermo-mechanically affected zones near the weld margin are oriented along with the flow direction of the plasticized material. The microhardness of the joint presents a global increase from the base metal to the weld interface by about 1700 MPa; the tensile strength of the joints ranges from 683 MPa to 717 MPa at ambient temperature, which is comparable to that of the base metal. The refinement strengthening contributes to enhancing the joint strength.