| Al-Si alloys have low density,high specific strength,heat resistance,wear resistance,excellent casting performance,good thermal stability and low thermal expansion coefficient.Al-Si alloys are widely used to engine piston,cylinder head,cylinder,wheel and all kinds of mechanical and electrical products in industrial production.Components which are made of AlSi alloy have a longer service life than ordinary aluminum alloy components.Northeastern University has developed a new type of Mg-contained high-Si aluminum alloy,which has the independent intellectual property rights in our country.The alloy doesn't only have the advantages of Al-Si alloy,but also has excellent mechanical properties and good plasticity.Comparable to that of the 6xxx series alloys.Until now,the study on the effect of alloying elements in Al-12.7Si-0.7Mg alloy is not comprehensive,especially the effect of Mn element on the microstructure and mechanical properties of Al-12.7Si-0.7Mg alloy has not been obtained yet.Aiming at semi-continuous casting Al-12.7Si-0.7Mg-xMn aluminum alloy prepared by our laboratory,we study on microstructure and mechanical properties of the Mn content in the hot rolled and cold rolled Al-12.7Si-0.7Mg alloy after solid solution-aging treatment.At the same time,we also study the influence of different heat treatment on the fracture behavior of Al12.7Si-0.7Mg-0.5Mn alloy hot rolled sheet.The results of the study are as follows:(1)Hot rolled and cold rolled Al-12.7Si-0.7Mg-xMn alloy with 1 mm is treated of solid solution aging treatment with 540?×1 h+170?×10 h.There are a large number of globular gray silicon particles and light gray or bright white AlFeMnSi phase in the matrix.The number of AlFeMnSi with light gray or bright white was increased with the increase of Mn content.For Al-12.7Si-0.7Mg-2.1Mn alloy sheet,the number of bright white Mn phase in hot rolled sheet and the size of this kind of Mn containing alloy is larger than that in cold rolled sheet.(2)Hot rolled and cold rolled Al-12.7Si-0.7Mg-xMn alloy with 1 mm is treated of solid solution aging treatment with 540?×1 h+170 ?×10 h.The yield strength and tensile strength increase after first decrease,then decrease with the increase of Mn content.(3)Hot rolled and cold rolled Al-12.7Si-0.7Mg-xMn alloy being treated of solid solution aging treatment,elongation rises first then falls with increase of Mn content.When the content of Mn is about 0.50%,the plastic of the hot rolled sheet and cold rolled sheet is the best,and the elongation of the alloy sheet decreases with the increase of Mn content.The elongation of hot rolled sheet with the same Mn content was higher than that of the cold rolled sheet.(4)In the tensile process of Al-12.7Si-0.7Mg-0.5Mn alloy sheet,silicon particles in the matrix plastic deformation does not occur,a small number of large size silicon particles fragmentation,silicon particles hardness did not change significantly before and after fracture,the matrix hardness increases.(5)When the hardness of the Al-12.7Si-0.7Mg-0.5Mn alloy matrix is higher than 80 HV and the small size of silicon particles distribute uniformly,there are two fracture paths.One is bypassing the silicon particles with small size(3 ?m-8 ?m).Another is passing through the silicon particles of irregular shapes with size more than 8 ?m and the small and gathering silicon particles of irregular shapes.The number of cracks in matrix is relatively less.(6)When the hardness of the Al-12.7Si-0.7Mg-0.5Mn alloy matrix is less than 60 HV and the small size irregular silicon particles gather more,the fracture path mainly passes the small and gathering silicon particles of irregular shapes(3 ?m?8 ?m).The number of cracks in matrix is relatively more and the size of cracks is larger. |
PDF Full Text Request