Microstructure and mechanical properties of Al–Li alloy manufactured by additive friction stir deposition

Abstract

The microstructure and mechanical properties of 2195 Al–Li alloy manufactured by additive friction stir deposition (AFSD) were thoroughly investigated before and after various post-heat treatments. The 4-layer built sample is characterized by the distinct layer-dependent microstructure, i.e., the grain size, texture, and precipitate, and resultant heterogenous mechanical properties, owing to the layer-dependent thermal histories of each layer. Post-heat treatments can significantly improve the mechanical strength and reduce the layer-dependent mechanical properties, via introducing the nanosized T1-phase. The AFSD Al–Li alloy after solution treatment and artificial aging achieved the max YS of 491.1 MPa and max UTS of 505.0 MPa. However, the ductility of the alloy is concomitantly reduced by the presence of precipitate free zones (PFZ) along grain boundaries after post-heat treatments. For the bottom layers, EL of AFSD-A and AFSD-ST-A samples are decreased by 65.3% and 76.2%, respectively, compared to AFSD.