High-strength aluminum alloy processed by micro laser powder bed fusion (μ-LPBF): Coordination of laser formability, microstructure evolution, and mechanical properties

• Published in: Journal of materials processing technology Vol. 332; p. 118580
• Main Authors: Liu, He, Gu, Dongdong, Shi, Keyu, Zhang, Han, Li, Linxuan, Zhang, Yijuan, Li, Jingyang, Qi, Junfeng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: High precision additive manufacturing; High strength aluminum; Mechanical property; Micro laser powder bed fusion; Microstructure; High precision additive manufacturing; Microstructure; Micro laser powder bed fusion; Mechanical property; High strength aluminum
• ISSN: 0924-0136
• DOI: 10.1016/j.jmatprotec.2024.118580

As the scale of additive manufacturing process (e.g., laser spot size, powder particle size, powder layer thickness) decreases, the application of micro laser powder bed fusion (μ-LPBF) involves novel mechanisms for process, microstructure and performance coordination. This study provides a systematic view of the processing window and performance enhancement of high-strength Al-Mg-Sc-Zr alloy fabricated by μ-LPBF. The effects of μ-LPBF parameters on defect control and densification activity of the printed parts were analyzed, so as to obtain the suitable processing window. The influence of building orientation and heat treatment on microstructural characteristics and mechanical properties of μ-LPBF processed parts was studied. The μ-LPBF Al-Mg-Sc-Zr exhibited sound surface quality (Ra of 6.088 μm) and considerably refined grains with an average size of 1.102 μm, which was related to the high cooling rate (8.6 × 107 K/s) induced by a small-sized laser beam (25 μm) and a tiny powder particle size distribution (2–20 μm) applied in μ-LPBF. After aging treatment (325 °C/4 h), the superior ultimate tensile strength of 590.24 ± 4.75 MPa combined with the sufficiently high elongation of 11.99 ± 1.17 % was achieved. Due to the significantly decreased scale of μ-LPBF production, the anisotropy caused by the variation of building directions was negligible. These enhanced mechanical properties were attributed to the combined effect of the grain size refinement, the higher number density (1.2 × 1024/mm3) of interior precipitates within grains, and the small-sized molten pool size of μ-LPBF. Computational fluid dynamics (CFD) simulation was applied to reveal the molten pool thermodynamics, indicating that a higher thermal temperature gradient (up to 9.8×107 K/m), a smaller molten pool size (with the width of 38.7–69.8 μm and depth of 8.7–30.0 μm) were generated in μ-LPBF. This work presents great potential in processing high-precision metallic components with fine structural feature size and satisfactory manufacturing quality. [Display omitted] •High-strength Al-Mg-Sc-Zr alloy was fabricated by micro laser powder bed fusion.•The processing-parameters-related densification behavior was studied and the processing window was determined.•The surface quality and mechanical performance were improved synergistically.•Negligible anisotropy of mechanical properties induced by the building direction was achieved.