Mao Hongkui, Bai Xiaoyu, Song Feng, Song Yuewen, Jia Zhe, Xu Hong, Wang Yu
School of Materials Science and Engineering, North University of China, Taiyuan 030051, China.
Materials (Basel). 2022 Jul 22;15(15):5101. doi: 10.3390/ma15155101.
Multi-stage heat treatment is an important method to improve the mechanical properties of Al-Si-Cu-Mg aluminum alloys. In this paper, the multi-stage heat treatment was carried out for the Cd-free and Cd-containing alloys. The experimental results show that the addition of Cd promoted the precipitation of Q″ and θ″, which led to the formation of a large number of fine, dispersed precipitates and a higher yield strength (YS) and ultimate tensile strength (UTS) for the Cd-containing alloys. The addition of Cd also altered the optimal heat treatment parameters. For the Cd-free alloys, the Cu-rich phase fully dissolved after three-stage heat treatment, and the YS and UTS of the three-stage heat-treated alloys were higher than their two-stage heat-treated counterparts. For the Cd-containing alloys, the three-stage heat treatment led to the precipitation of Cd-rich low melting point phases, caused defects, and reduced the mechanical properties of the alloy. The size and volume fractions of the precipitates were significantly less than those of the alloys after two-stage heat treatment and the strength of the alloys decreased. Therefore, the solution time should be strictly controlled for Cd-containing Al-Si-Cu-Mg alloys.
多阶段热处理是提高Al-Si-Cu-Mg铝合金力学性能的重要方法。本文对无镉和含镉合金进行了多阶段热处理。实验结果表明，添加镉促进了Q″和θ″相的析出，导致含镉合金形成大量细小、弥散的析出相，并具有较高的屈服强度（YS）和抗拉强度（UTS）。添加镉还改变了最佳热处理参数。对于无镉合金，经过三阶段热处理后富铜相完全溶解，三阶段热处理合金的YS和UTS高于两阶段热处理合金。对于含镉合金，三阶段热处理导致富镉低熔点相析出，产生缺陷，降低了合金的力学性能。析出相的尺寸和体积分数明显小于两阶段热处理后的合金，合金强度降低。因此，对于含镉的Al-Si-Cu-Mg合金，应严格控制固溶时间。
