Effect Of Mg Content On Microstructure And Properties Of Al-10Si-2.5Cu Alloy By Squeeze Casting

As one of the important ways to save energy and reduce emissions,lightweighting has always been the driving direction of the automotive industry.Among them,how to realize the replacement of steel materials with aluminum alloys,develop high-strength and high-toughness aluminum alloys,and minimize the self-weight of automobiles,which has become a research hotspot in the direction of automobile lightweight.The development of new materials is the main means to achieve lightweight vehicles.In this paper,the Al-10Si-2.5Cu alloy was used as the base alloy,and the Mg content was increased by adding AZ91D alloy,and the effects of magnesium content on the microstructure and properties of the alloy were investigated by means of X-ray diffractometry,optical microscopy and scanning electron microscopy.The heat treatment process of the alloy with a magnesium content of 1.38%was also studied.The results showed that:As the magnesium content increases,the morphology of the eutectic Si phase in the alloy changes from strip to fiber and the size is significantly reduced.At the same time,the Al₈Mg₃FeSi₆ phase in the tissue gradually grows,and the splitting effect on the matrix increases.The tensile strength and elongation of the alloy increased first and then decreased with the increase of magnesium content.When the magnesium content was 1.38%,the tensile strength of the alloy reached a maximum of 289 MPa.When the magnesium content is 2.03%,the elongation of the alloy is 2.24%;the hardness of the alloy is gradually increased.When the magnesium content is 3.12%,the hardness reaches 121.8HV;the cleavage plane in the fracture of the alloy changes with the increase of magnesium content.It is small,the number of dimples increases,and the fracture mode transitions from quasi-cleavage fracture to brittle fracture.After heat treatment,the Si phase has the best spheroidization effect when the solid solution time is 6h,and the hardness reaches the maximum value of 131.3HV.With the increase of aging time,the precipitation phase in the alloy increases.When the aging time exceeds 7 h,the Si phase in the structure gradually becomes coarse.As the aging time increases,the tensile strength and fracture elongation of the alloy show a tendency to increase first and then decrease.When the time limit was 7h,the tensile strength and fracture elongation reached 342 MPa and 4.2%,respectively.When the time is 7h,the hardness of the alloy is 132HV.After the aging time reached 62 h,the hardness value of the alloy was almost unchanged.As the aging time increases,the dimples in the fracture gradually increase,and the fracture mode is ductile fracture.