Effects Of Asymmetric Rolling And Heat Treatment On Mechanical Properties And Microstructure Of AI-12.7Si-0.7Mg Alloy

Al-Si alloys are commonly used in automotive and aerospace industry due to their low thermal expansion coefficient, high wear resistance and thermal conductivity as well as good castability. However, application of Al-Si alloys as structural materials has not been seen in literature. In this paper, Al-12.7Si-0.7Mg alloy is used as research object. Asymmetric rolling, which can produce additional shear the deformation, has been introduced to provide an abundant deformation characteristic microstructure. On this basis, the solution and aging process of this alloy has been further studied to improve its mechanical properties.In the present study, these four factors, which include aging temperature, aging time, rolling temperature and reduction affect the mechanical properties of the alloy. Then, the alloy was rolled before solution, after solution in different rolling temperatures with different reduction, respectively. The optimum model which can improve the mechanical properties of alloys was obtained by comparing the results. The tensile strength was measured by room temperature. Micro-structural changes have also been analyzed through the application of metallurgical observation. The precipitation behavior during aging was examined and analyzed by TEM. The following results have been obtained:(1) By comparing different speed ratio models of rolling and heat treatment on extruded alloy Al-12.7Si-0.7Mg, when the ratio is 1.06 it was more effective to improve mechanical properties of the alloy.(2) By comparing different models, the way of alloy was rolled after solution has been proved to be a superior model to the rolled before solution.(3) Strength of extruded alloy Al-12.7Si-0.7Mg which was asymmetric rolled of 150℃ after solution treatment with the reduction of 50%, and followed by aging of 170 ℃×1 h can reach 395 MPa.(4) It can be observed that Si particles are broken in the metallographic specimens after the stretching experiment, indicating that Si phase plays an active role of the sharing load when the alloy was ruptured.(5) With increasing the ageing time and the deformation, the shape of precipitated phases of rolled alloys changes from dot to needle. However, the strength of the alloy decreased.It show that the doted-precipitated phase contributes to improving alloy intensity.