Research On The Microstructure And Mechanical Properties Of Die Casting AlSi10MgMn Alloy

In recent years the automobile industry has been made rapid progress in our country.As the environmental problem is increasingly aroused people’s concern, light weight,which is regarded as the major energy conservation and emissions reduction technology,has become one of the common issues of the automobile industry. Aluminum alloy, as onekind of light materials, is used more and more widely in the automobile industry. Diecasting technology is paid more attention to the auto parts, owing to its high materialutilization rate and the perfect surface quality etc.Die casting AlSi10MgMn alloy, which possess good casting ability, belongs toAl-Si-Mg-Mn high strength and toughness aluminum. Die casting parts have excellentmechanical properties, particularly die casting parts produced by high vacuum die castingtechnology (HVDC), which are allowed to be heat treated, their mechanical performancecould be further strengthened by heat treatment, therefore this kind of aluminum alloycould be applied more and more broadly to load structure parts or safety parts with thinwalls or complex geometry.Based on the self-developed high vacuum die casting technology (HVDC), this paperfocuses on several issues as follows: the effects of the cavity vacuum on the properties andmicrostructure of the die casting, the effects of T1, T5and T6heat treatment on theproperties and microstructure of AlSi10MgMn alloy die castings fabricated by HVDC, theeffects of the Mg content on the properties and microstructure of AlSi10MgMn diecastings produced by low vacuum and conventional die casting technology. The resultsindicated as follows:（1）The gas content in the die casting specimen could be dramatically reduced byHVDC. Compared with the conventional die casting technology, the strength toughnessindex for die castings fabricated by HVDC was increased by55.1%, and the tensilestrength, yield strength and elongation were increased by12.7%、38.4%、130.4%,respectively.（2）The mechanical properties of the die castings produced by HVDC could besignificantly improved by artificial aging, especially for the strength. When the agingtemperature was170℃, aging time was8hours, the tensile strength of the heat treatedcasts came to351.3MPa and yield strength came to248.9MPa,13%and30.5%higherthan that of the as cast, respectively.（3）The microstructure of the die casting components fabricated by HVDCcould be improved by T5heat treatment. The heat treated die castings could exhibit bothexcellent elongation and strength. When solution temperature was510℃, solution time was3hours, after water quenching, the aging temperature was155℃and aging time was2hours, by such heat treatment the elongation and strength toughness index of thespecimen was increased to9.2%and1163.9, respectively. During the solution treatment,the microstructure of the castings was changed significantly, the eutectic silicon was blewout and spheroidized, homogenized more evenly in the-Al solute.（4）Through the orthogonal test, the effects of the parameters of T6heat treatmenton the properties of the die castings were investigated, and the optimal T6heat treatmentperameters were investigated, and when the solution temperature was500℃, solution timewas2hours, after quenching, aging temperature was170℃, aging time was4hours, aftersuch heat treatment the results were as follows: The tensile strength was358.4MPa, theyield strength was286.6MPa, the elongation was6.1%and the HB was110.4, the strengthtoughness index was1103.8.（5）The gas content in the die castings could be also decreased by Low vacuum diecasting (LVDC), when the die casting components was subjected to short time hightemperature heat treatment, blisters could not be observed on the surface of the castingspecimen, and the dimension was kept stable. Thus the microstructure of the die castingspecimen was improved by LVDC, the elongation and the strength toughness of the diecastings were observed better performance by short time high temperature heat treatment.With respect to the die casting specimen, which need not be heat treated, the content ofMg should be controlled between0.4%~0.65%; with regard to die casting specimen,which need be artificial aging treated, the content of Mg should be0.2%~0.4%; for diecasting specimen, fabricated by conventional die casting, when the Mg content was0.06%,excellent strength and strength toughness were observed either for as casts or artificialaging treated.