Abstract
Heat treatment at different temperatures was carried out on a Ti3Al linear friction welding joint. The characteristics and evolution of the microstructure in the weld zone (WZ) and the thermo-mechanically affected zone (TMAZ) of the Ti3Al LFW joint were analyzed. Combined with the heat treatment after welding, the effect of the heat treatment temperature on the joint was discussed. The test results indicated that the linear friction welding (LFW) process can accomplish a reliable connection between Ti3Al alloys and the joint can avoid defects such as microcracks and voids. The weld zone of the as-welded Ti3Al alloy joint was mainly composed of metastable β phase, while the TMAZ was mainly composed of deformed α2 phase and metastable β phase. After being heat treated at different temperatures, the WZ of the Ti3Al LFW joint exhibited a significantly different microstructure. After heat treatment at 700 °C, dot-like structures precipitated and the joint microhardness increased significantly. Subsequently, the joint microhardness decreases with the increase in temperature. Under heat treatment at temperatures above 850 °C, the formed structure was acicular α2 phase and the joint microhardness after heat treatment was lower than that of the as-welded joint.
Highlights
As a type of Ti-Al series intermetallic compound, Ti3 Al-based alloys have better high-temperature performance, oxidation resistance, creep resistance, and higher service temperature than ordinaryTi alloys
In the linear friction welding (LFW) process, the main structures of the lamellar-equiaxed dual-state α + β type TC4 Ti alloy in the thermo-mechanically affected zone (TMAZ) are composed of deformed α phase and acicular martensite, while the weld nugget is composed of martensite [25,26]
Ti3Al LFW joint was characterized by a microstructure with gradient formed at different temperatures and the interface, resulting in a greater deformation of the microstructure
Summary
As a type of Ti-Al series intermetallic compound, Ti3 Al-based alloys have better high-temperature performance, oxidation resistance, creep resistance, and higher service temperature than ordinary. At a slightly lower cooling rate, a very hard α2 (martensite) phase forms in the joint and exhibits very high hardness and enhanced brittleness [8,9] Another problem in the fusion welding of Ti3 Al is that the thermo-mechanically affected zone (TMAZ) is overheated, and the grains are prone to undergo irreversible coarsening and exhibit significantly increasing brittleness. The LFW process is a thermo-mechanical coupling process that occurs under the action of axial and friction forces, heat generation, phase transformation, and deformation at the welding interface. In the LFW process, the main structures of the lamellar-equiaxed dual-state α + β type TC4 Ti alloy in the TMAZ are composed of deformed α phase and acicular martensite, while the weld nugget is composed of martensite [25,26]. The microstructural characteristics of the Ti3 Al alloy LFW joint and the effect of heat treatment on the microstructure and mechanical properties of the joints were analyzed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
