Effect of Al–Er–Zr Master Alloy on Grain Refinement After Heat Treatment
The effects of Al–0.5Er–0.2Zr and Al–1Er–0.25Zr (wt%) alloys on the grain size of high-purity aluminum after isothermal aging at 450 °C were studied by micro-hardness, scanning electron microscopy (SEM), optical microscopy, and transmission electron microscope (TEM). The experimental results showed that the Al3Er secondary phases precipitated uniformly after isothermal aging of Al–0.5Er–0.2Zr alloy. The content of Er element in Al–1Er–0.25Zr alloy was much larger than the maximum equilibrium solid solubility in aluminum. The primary phase was densely distributed in the matrix. In addition, a large number of Al3Er and Al3 (Er, Zr) phases matched with the matrix lattice have been precipitated during heat treatment. The heat-treated master alloys were added to the high-purity aluminum liquid, and the nucleation sites were provided by the micron-sized and nano-sized precipitation phases. At last, the average grain size obtained by the refinement experiment was less than 300 μm. At the same time, the reasons for the refinement effect of the interaction between Er and Zr elements were preliminarily analyzed.
KeywordsAluminum alloy Master alloy Grain refinement Rare earths
The authors are pleased to acknowledge financial support received from the following projects (in no particular order). The National Key Research and Development Program of China (2016YFB0300804 and 2016YFB0300801), and the National Natural Science Fund for Innovative Research Groups (Grant No. 51621003). The Construction Project for National Engineering Laboratory for Industrial Big-data Application Technology (312000522303). National Natural Science Foundation of China (No. 51671005 and 51701006), Beijing Natural Science Foundation (2162006) and Program on Jiangsu Key Laboratory for Clad Materials (BM2014006).
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