Investigation On Microstructure And Properties Of Spray Forming Al-22Si-5Fe-3Cu-1Mg-xMn Alloy

High silicon aluminum alloy is widely used for engine cylinder and piston material for its many outstanding properties such as light quality, good wearing resistance and so on. With the development of modern automobile industry, the material properties have also been put forward higher requirement, but the coarse primary silicon phase in the high silicon aluminum alloy is the main factor to limit its application. In this article, the Al-Si-Fe-Mn-Cu-Mg-x-Mn-based alloy was prepared by spray forming technique.Compared to that of traditional casting, the microstructure of high silicon aluminum alloy which is made by spray forming technology is obvious refinement and the small particle of second phase uniformly distributes in the matrix. There is no eutectic structure appearing in the alloy and the size of the primary silicon crystal is between2～8μm.Under this experimental condition, Mn element can transform the needle-like iron-rich phase into the granular Al15(Mn,Fe)3Si2phase, thus effectively improve the alloy properties through reducing the fragmentation of alloy microstructure which caused by the needle-like phase. Most of the pores in the deposited alloy disappear after hot extrusion and the alloy microstructure is further refinement with the primary silicon being crushed. The phase composition of extruded alloy is consistent with deposited alloy and there does not produce a new intermetallic compound phase.The alloy using T6heat treatment of solution and aging process. After heat treatment the shape of the primary silicon phase becomes more rounded and the quantity of small particles of second phase is increased significantly as the alloy precipitates. This is not a significant growth in the size of the alloy grain.The tensile strength of the alloy first increases and then decreases with the increasement of the Mn contents. The best mechanical properties of the alloy appear when the Mn/Fe ratio reaches0.6. In this case the tensile strength was466.4MPa at room temperature and285.6MP at300℃.The results show that the alloy have an excellent heat resistance. The strengthening mechanism of the alloy mainly due to the high volume fraction of the dispersed phase in the alloy which has a high melting point that increases the resistance of the movement of the dislocation, thus improving the strength of the alloy.