Microstructure and mechanical properties of die-cast AZ91Dmagnesium alloy by Pr additions
(1. Department of Materials Science and Engineering, Key Laboratory of Advanced Structrural Materials
of Ministry of Education, Changchun University of Technology, Changchun 130012, China;
2. State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, China;
3. R&D Centre of Foundry Corporation, FAW Group Corporation, Changchun 130062, China;)
of Ministry of Education, Changchun University of Technology, Changchun 130012, China;
2. State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, China;
3. R&D Centre of Foundry Corporation, FAW Group Corporation, Changchun 130062, China;)
Abstract: Mg-9Al-xPr (x=0.4, 0.8 and 1.2, mass fraction, %) magnesium alloys were prepared by high-pressure die-casting technique. The effects of Pr on the microstructures of die-cast Mg-9Al based alloy were investigated by XRD and SEM. Needle-like Al11Pr3 phase and polygon Al6Mn6Pr phase are found in the microstructure. With 0.4% Pr addition, fine needle-like Al11Pr3 phase and a small amount of polygon Al6Mn6Pr phase near the grain boundary are found in the microstructure. Increasing Pr addition to 0.8%, lots of coarse needle-like Al11Pr3 phase within grain and polygon Al6Mn6Pr phase on grain boundary are observed. Further increasing Pr addition, the size of needle-like Al11Pr3 phase decreases, while the size of polygon Al6Mn6Pr relatively increases. The mass fraction of Pr at around 0.8% is considered to be suitable to obtain the optimal mechanical properties. The optimal mechanical properties are mainly resulted from grain boundary strengthening obtained by precipitates and solid solution.
Key words: praseodymium; magnesium alloy; microstructure; mechanical properties