Effect of thermal cycling on microstructure and mechanical properties of 2A97 Al–Li alloy fabricated by direct laser deposition

Direct laser deposition (DLD) is a potential approach to prepare large-scale metal component. This work focuses on understanding microstructural characteristics and mechanical properties along deposition direction of 2A97 Al–Li alloy fabricated by direct laser deposition. As-deposited sample showed coarse equiaxed grains at top and columnar crystals at middle and bottom. Growth texture of as-deposited sample along <001> was relatively obvious, value of which increased first and then decreased from bottom to top. Thermal cycle led to different kinds and distribution of precipitated phases along deposition direction, which affected microhardness and tensile strength. T₁ phase and a small amount of T₂, T_B phase precipitated at top. Effect of thermal cycle from top to bottom gradually increased, resulted in δ′, T₂, T_B phase coarsened. As a result, microhardness decreased from top (99 HV) to bottom (75HV). The sample in bottom showed an ultimate tensile strength (UTS) of 232.9 ± 4.3 MPa, and elongation of 9.5 ± 1.4%. While, ultimate tensile strength was increased to 268.5 ± 5.2 MPa, and elongation was 12.5 ± 0.9% in middle part, which was close to that of sample at top.