Aging responses of an Al-Cu alloy fabricated by selective laser melting

Abstract Aging responses of selective laser melted AlCu5MnCdVA alloys were investigated in this work. After artificial aging treatment, the precipitate strengthening makes the greatest contribution to the strength. At a lower aging temperature (426 K), nano-sized precipitates including AlxCuyMnz result in a limited sacrifice of the plasticity but a significant improvement in strength in the early stage. As the aging duration increases, θ'' and θ' precipitates nucleate, which can strongly improve the strength. Samples aged for 48 h have the highest ultimate tensile strength (473 MPa) due to the presence of θ' with high aspect ratio and dispersed θ''. At a higher aging temperature (446 K), The mixed θ'' and θ' layer structured precipitates contribute to the mechanical properties of the samples aged for 6 h and 10 h. The precipitate growth and the θ'' to θ' transformation both significantly affect the strength and ductility trade-off. Because the interfacial energy of θ'' is smaller than that of θ', the coarsening rate of θ'' is slower. As a result, the in-situ transformed θ' is smaller compared with the θ' nucleating at the defects, which is beneficial for the strength increase. The loss of Cd during SLM is one of the main reasons for the inapplicability of the traditional aging methods. The results highlight the importance of controlling the precipitates through post-aging process.