Comparison of AlSi7Mg0.6 alloy obtained by selective laser melting and investment casting processes: Microstructure and mechanical properties in as-built/as-cast and heat-treated conditions

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2020-03, Vol.778, p.139124, Article 139124
• Main Authors: Pereira, Juan Carlos, Gil, Emma, Solaberrieta, Leire, San Sebastián, María, Bilbao, Yoana, Rodríguez, Pedro Pablo
• Format: Article
• Language: English
• Subjects: Aeronautics; Aging (metallurgy); AlSi7Mg0.6 alloy; Aluminum base alloys; Casting; Construction; Emission analysis; Field emission microscopy; Heat treating; Heat treatment; Investment casting; Laser beam melting; Mechanical properties; Microhardness; Microstructure; Rapid prototyping; Selective laser melting; Tensile tests
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2020.139124

AlSi7Mg0.6 alloy is widely used in the automotive and aeronautical industries, and metal additive manufacturing (AM) is a breakthrough technology that motivates foundry companies to explore its potential in these industries; however, there is no deep knowledge of the mechanical properties and their relationship to microstructure in parts obtained by selective laser melting (SLM), as there is for parts obtained by casting. In this work, a comparison of the microstructure and mechanical properties of AlSi7Mg0.6 alloy obtained by SLM and investment casting processes was made. The mechanical properties of tensile specimens processed by both technologies were evaluated by uniaxial tensile tests and microhardness measurements in as-built/as-cast and heat-treated conditions with different build orientations in the case of SLM. An advanced characterization of the microstructure by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD) analysis was also performed. After analyzing the microstructure and mechanical properties obtained with different heat treatments, the strengthening mechanisms of the two processes were identified. It is possible to obtain improved mechanical properties with SLM processing, exceeding the typical values required for aeronautical parts obtained in investment casting heat-treated (T6), and the ductility is satisfactory. Direct aging after SLM processing can effectively strengthen the AlSi7Mg0.6 alloy and is the more effective way to improve the as-built mechanical properties. •AlSi7Mg0.6 alloy by additive manufacturing and investment casting processes were obtained.•Both processes generate quite different microstructures for the AlSi7Mg0.6 alloy.•Direct aging modify the silicon cells, making them smaller and better distributed.•High strength and improved ductility have been obtained with direct aging.•Natural aging, grain boundary and solid solution seem to be the main strengthening mechanisms.