Microstructure and mechanical properties of friction spot welding aluminium–lithium 2A97 alloy

• 2A97 Al–Li alloy was successfully welded by friction spot welding method.
• Microstructure and mechanical properties of FSpW 2A97 were investigated.
• Ageing processes with and without solution treatment were performed on FSpW 2A97.
• Mechanical properties of FSpW 2A97 were improved after solution and ageing treatment.

In this study, we investigated the microstructure and mechanical properties in different regions of the friction spot welded 2A97 aluminium–lithium alloy subjected to different heat treatment processes. The 2.0 mm thick hot-rolled sheet of 2A97 alloy was successfully welded using friction spot welding method with optimised welding parameters. Afterwards, the as-welded 2A97 joints experienced two subsequent heat treatment procedures: solution and ageing; directly ageing. The corresponding microstructure and mechanical properties of the heat-treated specimens were studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness test and tensile test. The results show that the mechanical properties of the 2A97 joints before and after heat treatment were significantly modified, which was mainly related to fine-grained microstructure, size and type of precipitates, and dislocation density. Compared to the base material and the material that only experienced direct ageing, the whole friction spot welded 2A97 joint after solution and ageing treatment delivered better mechanical properties.

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