Study On The Structure And Properties Of 6016 Aluminum Alloy With Composition Gradient Change

Al-Mg-Si Aluminum Alloy with medium strength has good formability and corrosion resistance,and is one of the best materials for lightweight automobile.In this paper,6016 aluminum alloy is taken as the research object,and a new high-throughput preparation method is designed Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM),electron back scattering diffraction(EBSD)were used.The effects of Mg/Si mass ratio,Mg and Si alloy content on the microstructure and properties of as cast and as rolled alloys were studied by means of microhardness and tensile properties tests.The evolution of microstructure and properties of the alloy during rolling was discussed,and the influence of heat treatment system on the properties of the alloy was analyzed.The results are as follows:(1)With the increase of Mg/Si mass ratio,the grains of 6016 aluminum alloy are refined as cast and rolled.The hardness of as cast alloy increases,the conductivity decreases,and the yield strength and tensile strength of rolled sheet increase,but the elongation changes little.(2)There are mainly black irregular Mg2Si phase,gray AlMnFeSi phase,slender AlFeSi phase and a small amount of Q phase(AlCuMgSi)in the as cast structure of 6016 aluminum alloy.After homogenization at 550?/8h,most of the non-equilibrium phases in the alloy melt into the matrix,leaving only a small amount of residual phase.(3)During the hot rolling of 6016 alloy,there are mainly small angle grain boundaries,such as Brass R {111}<110>and {111}<112>,Y {110}<111>,{114}<481>and recrystallization texture Cube {001}<100>.After the first cold rolling,the small angle grain boundary began to shift to the large angle grain boundary,the strength of Brass R {111}<110>and {111}<112>decreased,the {114}<481>gradually changed to Y {110}<111>.After intermediate annealing at 360?/2h,the large angle grain boundary increased rapidly,the strength of Cube {001}<100>increased greatly,and the Brass R texture decreased gradually.After the final cold rolling,the main grain boundary is large angle grain boundary,the Brass R texture are enhanced,and a certain Cube {001}<100>is still retained,and a strong rotational Goss texture appears.With the increase of Mg and Si alloy elements,the recrystallization grains of the alloy sheet become smaller,the cube texture strength is weakened,and the mechanical properties of the sheet are improved obviously.(4)6016 alloy has the properties of artificial aging and bake hardening.With the prolongation of aging time and bake time,the hardness of the alloy increases,but the hardness regression phenomenon appears in the early stage of aging.The mechanical properties of three kinds of alloy plates with different Mg and Si contents have good mechanical properties,and with the increase of Mg and Si contents,the mechanical properties of alloy plates will be improved accordingly.The elongation of the three alloy plates is above 24%,the yield strength before baking is 154MPa,151MPa,131MPa respectively,and the yield strength after baking is 235MPa,228MPa,226MPa.The yield strength and tensile strength of the three kinds of pre-aged alloys increase continuously during the storage at room temperature.With the increase of storage time,the yield strength and tensile strength of the baked alloy decreased.