Adding rare earth elements into aluminum alloy not only has the effect of modification, but also can improve the mechanical properties. In order to improve the use performance of aluminum alloy and expand its application scope, rare earth alloying technology was used to treat aluminum alloy, and good results were achieved. As the addition of rare earth La alone has little effect on the mechanical properties of aluminum alloy, and the cost of Sc is high, the addition of two rare earth elements, Sc and La, not only reduces the amount of Sc added, but also significantly refines eutectic silicon, which greatly improves the mechanical properties of the alloy.
(1) The cast A356.2 (Sc, La) aluminum alloy added with two rare earth elements Sc and La has better refining effect of eutectic silicon than the A356.2 (La) aluminum alloy added with one rare earth element La alone, which can make the eutectic silicon from the original average size of 13.6 μ The average size of m is only 2.3 μ The morphology of eutectic silicon was improved obviously. The addition of a rare earth element La alone can only refine eutectic silicon to 6.3 μ ｍ。
(2) The tensile strength and elongation of A356.2 (Sc, La) aluminum alloy containing two rare earth elements Sc and La are significantly higher than those of A356.2 (La) aluminum alloy containing one rare earth element La. The tensile strength of aluminum alloy is increased from 136.22 MPa to 181.62 MPa, and the elongation is increased from 1.8% to 4.0%, which greatly improves the mechanical properties of aluminum alloy. The tensile strength and elongation of A356.2 (La) aluminum alloy containing a rare earth element La are 148.84 MPa and 2.3%, respectively, with a small increase.
(3) The rare earth Sc and La form Al3Sc phase, AlSc phase, Sc phase and La phase in the cast A356.2 (Sc, La) aluminum alloy, which are dispersed in the matrix and play the role of dispersion strengthening. At the same time, these phases prevent the growth of eutectic silicon, refine eutectic silicon, and form fine grain strengthening. Under the dual effects of dispersion strengthening and fine grain strengthening, the mechanical properties of the alloy are significantly improved.
At present, the domestic research on rare earth aluminum alloy mainly focuses on adding single rare earth, while there is no relevant report on casting A356.2 (Sc, La) aluminum alloy added with two kinds of rare earth elements. In this paper, the cast A356.2 (Sc, La) aluminum alloy was formed by adding two rare earth elements Sc and La, and its microstructure and mechanical properties were analyzed to provide theoretical and experimental basis for optimizing the process.