Natural and artificial aging behaviour of Al-Cu-Mg-Ag-Ti-B (A205) alloy processed by laser powder bed fusion: Strengthening mechanisms and failure analysis

Abstract

The Al-Cu-Mg-Ag-Ti-B (A205) alloy has gained success in the additive manufacturing domain due to its good processibility. It is a precipitation hardening alloy, and because of this, its mechanical properties are greatly influenced by post-processing treatments. In the present work, A205 samples processed by laser powder bed fusion were first solution treated and then aged by: (i) natural aging (NA) and (ii) artificial aging (AA). The effects of different aging treatments on the microstructure and mechanical behaviour were evaluated. Both NA and AA heat treatments improved the mechanical behaviour of as-built A205 alloy. Peak hardness was achieved in 20 days (≈ 137 HV) for the NA specimen, whereas it took 4 h at 190 °C (≈ 144 HV) for the AA specimen. The average yield strength, ultimate tensile strength and elongation to fracture for NA and AA were, 276 MPa, 434 MPa, 20% and 397 MPa, 463 MPa, 11%, respectively. The structure-property corelation was analysed by evaluating various strengthening factors. Considerable grain boundary strengthening was observed in both NA and AA specimen. The major strengthening contributions in the NA specimen were due to the disordered Ag-Mg co-clusters and solid solution strengthening by Cu. In AA instead, strengthening due to the precipitation of plate-type Ω/θ’- Al2Cu phase was dominant. In the end, failure mechanisms in the NA and AA conditions were also briefly discussed. The laser powder fused A205 alloy demonstrated a significant response to the NA and possessed a high-ductility and good-strength combination.