| With the increasing emphasis on energy conservation, many auto partsmanufacturers start to think about the material selection requirements of automotivelightweight engineering. As the lightest metal material, there are many concerns andattentions on magnesium alloy. In this paper, automotive steering column bracket iscarried out the following research.According to casting weight and combining with manual and empirical data casting,the sprue, runner, the area of runner cross-sectional and the number of runners aredetermined, and the use of three-dimensional mapping software is built as athree-dimensional solid model to design two kinds of casting system, then the Flow-3Dsoftware is used to determine a better casting system by using the simulation of oxidefilm and the volume of gas defects in the bottom gating system and middle gating system,and the better casting system is bottom gating system. And the oxide film, volume of gasdefects and temperature field are simulated in filling process of bottom gating system topredict the possible location, and the location of the riser is verified.The two-factor experiment is used in different casting temperature and sandtemperature to simulate the oxide film and the volume of gas defects in filling process,and the best condition is that casting temperature in700℃and sand temperature in200℃.β phase is getting thinner and smaller and distributed more uniform, and α phase isgetting smaller than before, and the solid solution of Al, Mn, Zn, Ca and Y is appeared,and the UTS of the alloy is also improved when adding x%Ca,1%Y. The UTS reaches179.3MPa when the content of Ca is0.5%, which is higher than the content of Ca is1%.Meanwhile, β phase is getting bigger when the content of Ca is enhanced to1%. Afterheat treatment by T4, β phase is decomposed at first and then dissolved in the matrix andseparated out subsequently, and it is getting thinner and smaller than before anddistributes more uniform, and α phase is getting smaller,the UTS ofAZ91D+0.5%Ca+1%Y reaches187.6MPa which is also the higher one. After heattreatment by T6, β phase is decomposed at first and then dissolved in the matrix andseparates out subsequently, it is getting thinner and smaller than before and distributedmore uniform. With the increasing of aging time, β phase is getting thinner and smaller, but when the aging time reaches to12h, the size of β phase has an increasing trend, and αphase is getting smaller. Meanwhile, the UTS of the alloy reaches191.2MPa which is thehighest one, when the content of Ca is0.5%, and the aging time is10h.In this paper, the automotive steering column bracket is developed and the impact ofalloying elements on the microstructure and mechanical properties of the alloy isanalyzed, this can give a reference to the peer. |
