Study On Alloying And Heat Treatment Of AlMgSi

Automobile lightweight shows distinct impact on reducing energy and air pollution. The study of excellent aluminiun alloys for automobile have been taken more and more attention ,and the subject of formability and baking hardening of Aluminium alloys for automobile body sheet have important value on engineering.The present work has investigated the effect of different content of Cr and Ce, heat treatment on the microstructure and mechanical properties at room temperatures, by experimental methods such as optical microscopy (OM), scanning electron microcopy (SEM) with energy dispersive X-ray analyses (EDAX), microhardness tester and electronic tensile tester.The results shows that:As casted state,Cr mainly dissolves intoα-Al and forms unstable supersaturation solid solution, and then causes dispersion strengthening in the form of Al₇Cr phase,α-Al (Cr,Fe) Si phase, etc during the following homogenization treatment. When Cr element is added, alloys show upper the ultimate tensile strength ,however, the intensity increase little when the quantities exceed 0.1%.when 0.3%Cr is added and the numerical value can arrive at 16.5% as casted alloy. The casting structure is meliorated and refined, and dispersion phase is spured on the crystal boundary while the homogenization treatment by lanthanon element Ce.The tensile strength of alloys have marked increase when element Ce is added, but the elongation ration is little impressed. As casted alloy can get greatest mechanical properties when containing 0.2% Ce. however, when the quantities of element Ce over 0.3%, strengtheness of alloy is no more distinct. As casted state, AlMgSi alloys have good synthetical mechanical properties when 0.2%Ce and 0.3% Cr are added, and the tensile strength,yielding strength and elongation ration is 253 MPa,102MPa and 16.8%.Alloys with solution treatment at 550℃for 30min have preferable synthetical mechanical properties after aging treatment ,and the tensile strength,yielding strength and elongation ration is 322MPa,188MPa and 22.5%. The longer alloys keep at room temperature after solution treatment ,the lower the strengthen is after the following artifical aging . however, propeeties of alloy that have pre-aging treatment is stable. Natural aging is not good for alloy aging hardening, and alloys could get better aging hardening while artifical aging in time. Pre-aging treatment inhibite deleterious effect of antural aging and enhance aging hardening.. Alloys have preferable hardness after pre-aging+natural aging+artifical aging and pre-aging +natural aging +baking treatment. Simulating baking is even up to that of sheet after artifical aging.