The Research Of The Microstrure And Property Of Multi-micro-alloying Aluminium Alloy

With the increasing of people’s material needs and the continuous developing of science and technology, the aluminum alloy which is one of the most important light metal materials faces more serious challenges. A356aluminum alloy is typical casting aluminum alloy which widely used in fields such as aerospace, automobile and motorcycle industry and its mechanical performance is the main index.In addition, A356aluminum alloy which is used to produce the cars’ wheel hub frequently works in a poorer condition. So the corrosion resistance becomes one of its important index.This paper investigates the effect of microalloying with the different content of rare earth La and Y element on the microstructure and property of A356aluminum alloy and want to modify the the microstructure and property of A356aluminum alloy by this way. The experiment shows that adding the rare earth La element can improve the partial aggregation of the eutectic silicon in A356aluminum alloy. When the addition amount of rare earth La element is0.25wt.%, the phenomenon of the partial aggregation of the eutectic silicon rarely disappear, but the effect of the grain refinement is unconspious. With the increasing of rare earth La element’s addition (0~0.25wt.%), the hardness and corrosion resistance of A356aluminium alloy is improved.Adding the rare earth element rare earth Y element not only effectively modifies the eutectic silicon of the test alloy, but also refines the a-Al grain. When the addition amount of Y element is0.15wt.%, the effect of modifying of eutectic silicon and refining ofa-Al grain is the best. With the increasing of rare earth Y element’s addition (0-0.5wt.%), the hardness and corrosion resistance of A356aluminium alloy becomes better.Compound addition of rare earth La and Y elements can remarkable modify the eutectic silicon and refine the a-Al grain of the alloy and this effect is much better than adding rare earth La or Y element. When the compound addition is0.15wt.%La,0.2wt.%Y, the morphologies of the eutectic silicon are modified from a coarse strip or rod-like to granular or spherical, and they distribute in grain boundary equally. The grain’s size firstly increases and then decreases with the additions of rare earth La,Y elements.When the compound addition is0.15wt.%La,0.2wt.%Y, the large dendritic crystal of alloy’s microstructure almost disappear. When the compound addition is0.15wt.%La,0.3wt.%Y, the a-Al grain is mininum. The hardness and corrosion resistance of the A356is improved remarkablely, and strengthened and then weakened with the increasing of rare earth La,Y elements. In the process of microalloying, the corrosion resistance of alloy is improved notably when compound addition is0.15wt.%La,0.2wt.%Y and the hardness and corrosion resistance of alloy is the best when compound addition is0.15wt.%La,O.3wt.%Y,this effect is much better than adding rare earth La or Y element.T6heat treatment can make the eutectic silicon of the alloy spheroidizing and homogenizing in the test, at the same time the phenomenon of partial eutectic silicon’s aggregation is improved, a-Al grains is fined significantly in this alloy and the corrosion resistance of alloy is increased notably.The test results show the effect of micro alloying with the rare earth La and Y element of A356aluminum alloy is still significant after T6heat treatment.