Li Kai, Yu Yan, Lu Qiang, Li Yuanfei, Yan Qiao, Lan Xinyue, Li Liya, Chen Baishan, Song Min
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China.
Institute for Advanced Study, Central South University, Changsha 410083, China.
Materials (Basel). 2023 Sep 6;16(18):6091. doi: 10.3390/ma16186091.
Cu additions notably strengthen Al-Mg-Si and Al-Si-Mg alloys due to the dense precipitation of quaternary nano precipitates during ageing. However, the chemical evolution and mechanical behaviors of the quaternary micro-scale Q constituent phase occurring in cast and homogenized states have rarely been studied. Meanwhile, there exists a type of AlCuMgSi cluster in the cast state, which has been regarded as Q particles. The accurate identification of phase constituents is the basis for the future design of alloys with better performance. In our work, this type of cluster was revealed to consist of α-Al, θ-AlCu, Q, and Si phases through micro-to-atomic scale studies using scanning and transmission electron microscopes. The skeleton of the dendrite was θ phase. The second phases in the dendritic eutectic cluster dissolved quickly during a 4 h homogenization at 550 °C. The Q phase was found to effectively absorb the Fe impurities during casting and homogenization. As a result, the formation of other harmful Fe-rich intermetallics was suppressed. These Q constituent particles were observed to break into separate pieces in an intermediately brittle manner when compressed in situ in a scanning electron microscope. These findings provide insights into the thermodynamic modeling of the Al-Mg-Si-Cu system and alloy design.
由于时效过程中会析出致密的四元纳米析出相，添加铜显著强化了Al-Mg-Si和Al-Si-Mg合金。然而，对于铸态和均匀化状态下出现的四元微米级Q组成相的化学演变和力学行为，鲜有研究。同时，铸态存在一种AlCuMgSi簇，它被视为Q粒子。准确识别相组成是未来设计性能更优合金的基础。在我们的工作中，通过使用扫描电子显微镜和透射电子显微镜进行微观到原子尺度的研究，揭示了这种簇由α-Al、θ-AlCu、Q和Si相组成。枝晶的骨架是θ相。在550℃下进行4小时均匀化处理时，枝晶共晶簇中的第二相迅速溶解。发现Q相在铸造和均匀化过程中能有效吸收铁杂质。结果，抑制了其他有害富铁金属间化合物的形成。在扫描电子显微镜中原位压缩时，观察到这些Q组成颗粒以中等脆性的方式破碎成单独的碎片。这些发现为Al-Mg-Si-Cu系统的热力学建模和合金设计提供了见解。
