Evolution of the microstructure and mechanical properties of additively manufactured AlSi10Mg during room temperature holds and low temperature aging

• Published in: Additive manufacturing 2020-12, Vol.36, p.101429, Article 101429
• Main Authors: Fite, John, Eswarappa Prameela, Suhas, Slotwinski, John A., Weihs, Timothy P.
• Format: Article
• Language: English
• Subjects: Aging; AlSi10Mg; Powder bed fusion; Precipitation; Room temperature; XRD
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2020.101429

[Display omitted] •We report room temperature evolution of the AlSi10Mg microstructure.•We infer details of the thermal history during the build from the as-built microstructure.•We monitor the progression in dissolved Si both at room temperature and at 170 °C.•We report higher hardness values through alternative post processing.•We demonstrate remarkable hardness stability even after extreme over-aging at 170 °C. Conventional thermal processing may not always be well-suited for modifying the unique, as-built microstructure of Additively Manufactured (AM) AlSi10Mg. Conventional post-build processing of AM AlSi10Mg components involves a Solution Heat Treatment (SHT) at elevated temperatures (∼500 °C) followed by low-temperature aging (170 °C). Here we characterize low-temperature aging (170 °C) of AM AlSi10Mg components both with and without a conventional solution heat treatment. The samples without a solution heat treatment are first held at room temperature for several months, during which we monitored the reduction of Si in the Al matrix, from 4.74 to 3.98 at% with limited changes in hardness. We also correlate the as-built microstructure back to the processing conditions. During the room temperature hold, and when these samples are subsequently aged at 170 °C without a solution heat treatment, they retain a eutectic ribbon microstructure but lose the supersaturation of Si within the Al matrix with aging. These samples reach a peak hardness after 2 h at 170 °C that is approximately 50 % higher than the peak hardness of SHT samples after 5 h at 170 °C. We contrast the microstructure and density changes resulting from both heat treatment paths and explain how this modified heat treatment complements AM AlSi10Mg’s unique, as-built microstructure.