Mechanical properties of rheo squeeze casting aluminum alloy parts

In the middle part of the rheo indirect squeeze casting part, a rectangular sample with a thickness of 2mm was taken for tensile test according to the national standard. The size of the rectangular tensile sample is shown in the figure. The mechanical properties test results show that the product has stable properties, the average tensile strength is 190.5mpa, the average elongation is 13.13%, and the maximum elongation is more than 19%. Because the alloy melt crystallizes under pressure, the flowing melt contacts with the surface of the mold cavity quickly and forms a chilling layer, which is conducive to the stability of the interface. The indirect squeeze casting parts have higher density, finer intermetallic compounds, and higher strength and elongation after fracture. However, the elongation ratio of different parts fluctuates greatly, which is related to the involvement of oxide scale during sample processing or rheological forming . When the tensile specimen is tested, the specimen often breaks at both ends, and the fracture has obvious impurities that can be found by naked eyes. Because of the intrinsic problems of rheoforming such as inclusion defects and intergranular segregation, the mechanical properties are not stable and competitive, which will be the key problem to be solved in rheoforming. Due to the influence of equipment installation and debugging, the specific pressure of process experiment is not improved. With the increase of specific pressure, the density and strength will be improved.

According to the tensile test data of A356 alloy rheo squeeze casting parts after T6 heat treatment, T6 process is solution temperature 535 ℃, holding time 6h, water quenching, then aging treatment of 130 ℃, holding time 3H and air cooling. The results show that the properties of extruded castings after T6 treatment are stable, the average tensile strength is 241.99mpa, the average elongation is 14.46%, and the maximum elongation is 20.67%. Therefore, heat treatment can effectively improve the properties of A356 alloy in rheo squeeze casting. After solution treatment, the alloy elements dissolve into the base metal, the dislocation increases, resulting in lattice distortion, which increases the movement resistance of dislocation and enhances the material strength. At the same time, the strengthening phase Mg2Si is also fully dissolved in the α – Al alloy matrix to form solid solution strengthening. After aging treatment, the second phase particles in the matrix are more evenly distributed and dispersed, so that the strength of the alloy is improved. On the whole, the tensile strength is not very high, and the elongation ratio of different squeeze casting parts fluctuates greatly, which may be related to the formation of fine oxide scale and slag inclusion.

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