Effect of Cu/Mg-containing intermetallics on the mechanical properties of the as-cast HVDC AlSiMgMnCu alloys by SBFSEM at nano-scale

• Published in: Journal of alloys and compounds 2022-12, Vol.926, p.166837, Article 166837
• Main Authors: Liu, Fei, Zheng, Huiting, Zhong, Yan, Jiang, Yuanhang, Li, Xiang, Chen, Bo, Zhao, Haidong
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum base alloys; Copper; Cu/Mg ratio; Cu/Mg-containing intermetallics; Die casting; Elongation; High vacuum; High vacuum die casting (HVDC); Intermetallic compounds; Intermetallic phases; Magnesium; Mechanical properties; Microstructure; Nucleation; Serial block-face scanning electron microscopy (SBFSEM); Spatial distribution; Three dimensional analysis; Ultimate tensile strength
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.166837

In this study, AlSiMgMnCu alloys with different Cu and Mg contents were fabricated by high vacuum die casting (HVDC) technique. The phase formation and their microstructure evolution are quantitatively studied by serial block-face scanning electron microscopy (SBFSEM) at nano-scale in three-dimensions. Through analyzing their three-dimensional (3D) microstructure, effects of the spatial distribution, volume fractions and morphology of the intermetallic phases on the alloy’s mechanical properties are comprehensively discussed. It is found that, with higher Cu content and lower Mg content, the nucleation and growth of θ-Al2Cu phase would have advantage over Q-Al5Cu2Mg8Si6 phase. In contrast, decreasing Cu/Mg ratio by increasing Mg content is in favor of the nucleation and growth of the Q-Al5Cu2Mg8Si6 phase. The uniformly distributed fine θ-Al2Cu phase provides the highest contribution to the strengthening of the HVDC AlSiMgMnCu alloys. For the Cu/Mg ratio to be 3, an as-cast HVDC Al-10Si-0.2Mg-0.5Mn-0.6Cu alloy with optimized ultimate tensile strength, yield strength and elongation of 330 MPa, 162 MPa and 10.2%, respectively, had been produced. •3D microstructure of HVDC AlSiMgMnCu alloys with different Mg and Cu contents were quantitatively analyzed by SBFSEM.•Adding Cu enhances the growth of θ phase, and adding Mg enhances the growth of Q phase along the grain boundaries.•Fine and uniformly distributed θ phases make the highest contribution to the strengthening of HVDC AlSiMgMnCu alloys.