Affiliation:
1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
2. Institute for Advanced Study, Central South University, Changsha 410083, China
Abstract
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-Al2Cu, 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.
Funder
National Natural Science Foundation of China
Subject
General Materials Science
Reference44 articles.
1. The Aluminium Story;Bayliss;Alum. Int. Today,2014
2. The precipitation of the Q phase in an AA6111 Alloy;Weatherly;Metall. Mater. Trans. A,2001
3. Atomic model for GP-zones in a 6082 Al–Mg–Si system;Marioara;Acta Mater.,2001
4. Effects of strain rate on mechanical properties, microstructure and texture of Al–Mg–Si–Cu alloy under tensile loading;Wang;Trans. Nonferrous Met. Soc. China,2020
5. The Latest Trends in Aluminum Alloy Sheets for Automotive Body Panels;Sakurai;Kobelco Technol. Rev.,2008