Influence on microstructure, strength and ductility of build platform temperature during laser powder bed fusion of AlSi10Mg

• Published in: Acta materialia 2020-12, Vol.201, p.231-243
• Main Authors: Santos Macías, Juan Guillermo, Douillard, Thierry, Zhao, Lv, Maire, Eric, Pyka, Grzegorz, Simar, Aude
• Format: Article
• Language: English
• Subjects: aluminium alloy; damage initiation; Engineering Sciences; Laser powder bed fusion; Materials; microstructure; strengthening mechanism
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2020.10.001

AlSi10Mg manufactured by laser powder bed fusion (or selective laser melting) benefits from a very fine microstructure that imparts significant mechanical strength to the material compared to the cast alloy. The build platform temperature stands out as a significant processing parameter influencing the microstructure as it affects the cooling rate and thermal gradient during manufacturing. Setting the build platform temperature to 200°C yields a negligible residual stress level. However, the strength is lower compared to that obtained using a build platform temperature of 35°C, with a similar fracture strain. A detailed 3D microstructural analysis involving focused ion beam/scanning electron microscopy tomography was performed to describe the connectivity and size of the Si-rich eutectic network and link it to the strength and fracture strain. The coarser microstructure of the 200°C build platform material is more prone to damage. The α-Al cells as well as the Si-rich precipitates present a larger size in the 200°C material, the latter thus having a lower strengthening effect. The Si-rich eutectic network is also less interconnected and has a larger thickness in the 200°C material. An analytical model is developed to exploit these microstructural features and predict the strength of the two materials. [Display omitted]