Unique cellular microstructure-enabled hybrid additive and subtractive manufacturing of aluminium alloy mirror with high strength

• Published in: Journal of materials processing technology Vol. 320; p. 118095
• Main Authors: Bai, Yuchao, Lee, Yan Jin, Zhao, Cuiling, Yan, Qi, Guo, Yunfa, Shang, Yunshu, Wang, Hao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2023
• Subjects: AlSi10Mg; Hybrid manufacturing; Laser powder bed fusion; Machinability; Metal mirror; Ultra-precision machining; Machinability; Laser powder bed fusion; Hybrid manufacturing; Metal mirror; AlSi10Mg; Ultra-precision machining
• ISSN: 0924-0136
• DOI: 10.1016/j.jmatprotec.2023.118095

The integrated design and manufacturing of aerospace metal optical mirrors can be challenging for rapid manufacturing with traditional techniques while maintaining mechanical integrity and meeting mass limitations. Hybridized additive/ultra-precision machining process is a promising approach to fabricate optical surfaces on AlSi10Mg alloy to meet the optical demands and mechanical performances. However, the fundamental investigation of ultra-precision machining of optical surfaces on additively manufactured AlSi10Mg alloy is still lacking, delaying the application of this technology. In this study, the microstructure, mechanical properties, and machinability of AlSi10Mg alloys produced by laser powder bed fusion (LPBF) were investigated, including the effect of heat treatment. A superior surface finish was achievable on the as-built alloy due to the unique fine cellular microstructure that aided the cutting process. Surfaces with roughness of ∼4 nm Ra and excellent mechanical properties with tensile strength of up to ∼491 MPa were obtained. In contrast, the large silicon particles that formed during heat treatment led to the deterioration of machined surface quality with an achievable roughness of ∼9 nm Ra along with the reduction in tensile strength to ∼283.5 MPa. Subsurface TEM analysis on the machined as-built sample indicated that the nano-scale silicon particles in the cellular microstructure boundary of the alloy and the semi-coherent relationship between silicon particles and the aluminum matrix avoided the generation of machined surface damages. New insights into the relationships between the additive manufacturing process, microstructure, and machinability are detailed to highlight the potential of hybrid manufacturing technology for high-strength and high-surface-quality parts.