Role of Direct Aging and Solution Treatment on Hardness, Microstructure and Residual Stress of the A357 (AlSi7Mg0.6) Alloy Produced by Powder Bed Fusion

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Vol. 52; no. 4; pp. 2484 - 2496
• Main Authors: Tonelli, Lavinia, Liverani, Erica, Morri, Alessandro, Ceschini, Lorella
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.08.2021; Springer Nature B.V
• Subjects: Aging; Aging (artificial); Alloys; Aluminum base alloys; Automotive parts; Characterization and Evaluation of Materials; Chemistry and Materials Science; Customization; Design optimization; Hardness; Heat treating; High temperature; Laser applications; Laser beam melting; Materials Science; Metallic Materials; Microstructure; Nanotechnology; Original Research Article; Powder beds; Process heat; Residual stress; Solid solutions; Solution heat treatment; Structural Materials; Surfaces and Interfaces; Thin Films; Weight reduction
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-021-02179-6

Applying additive manufacturing (AM) technologies to the fabrication of aluminum automotive components, with an optimized design, may result in improved vehicle light weighting. However, the post-process heat treatment of such alloys has to be customized for the particular AM microstructure. The present study is aimed at investigating the effect of different heat treatments on the microstructure, hardness and residual stress of the A357 (AlSi7Mg0.6) heat-treatable alloy produced by laser-based powder bed fusion (LPBF, also known as selective laser melting). There are two major issues to be addressed: (1) relieving the internal residual stress resulting from the process and (2) strengthening the alloy with a customized heat treatment. Therefore, stress-relief annealing treatment, direct aging of the as-built alloy and a redesigned T6 treatment (consisting of a shortened high-temperature solution treatment followed by artificial aging) were examined. Comparable hardness values were reached in the LPBF alloy with optimized direct aging and T6 treatments, but complete relief of the residual stress was obtained only with T6. Microstructural analyses also suggested that, because of the supersaturated solid solution, different phenomena were involved in direct aging and T6 treatment.