Effect Of Mg And Rare Earth Elements On Microstructure And Mechanical Properties Of Al-20%Si Alloy

Al-Si alloy was widely used because the rapid development of automobile industry, while energy conservation become to the word’s theme with the depletion of energy, this ask material be more light. As we all known Mg element addition to Al-20%Si can effectively improve the performance,and simultaneously reduce the quality of the alloy, but generated coarse Mg2Si will reduces the performance of the alloy with the increase of Mg contents. Therefore, refined and heat-treated usually were used to modify Al-Si alloy, the paper studied the effects of rare earth elements Er and Ce on microstructure and mechanical properties of Al-18%Si-10%Mg alloy. OM and SEM were used to observe the microstructure, XRD and EPMA were employed to composition analysis. After have tested the alloy samples’hardness, friction and other mechanical performance, we concluded that:(1) Add Mg element can improve the microstructure of alloy, which can refine the primary silicon particles when the content is low, and hard Mg2Si phase beneficial to the performance of the alloy will produced with high Mg contents, the tensile strength and hardness was enhanced to46.7%and76.5%.(2) Rare earth elements Er added to the Al-18%Si-10%Mg alloy can effectively improve the microstructure and performance of the alloy, morphology of primary Mg2Si becomes small equiaxial and granular or lump particles with1.0%Er addition. The long plate phase changed into tiny dot-like or fibrous. Eutectic silicon also has been refined. These lead the alloy tensile strength and hardness increased by32.1%and19.6%, coefficient of friction and wear volume was reduced by7.8%and70%, respectively.(3) Rare earth elements Ce added to the Al-18%Si-10%Mg alloy can effectively improve the microstructure and performance of the alloy, morphology of primary Mg2Si becomes fine equiaxial and granular or block when0.8%Ce addition. Eutectic silicon also has been refined, but the phenomenon of deteriorate-modify appeared when the dosage of Ce is1.0%. The tensile strength and hardness of this kind alloy increased by29.8%and17.1%, friction coefficient and wear volume decreased by8.1%and74.3%.(4) Morphology of primary Mg2Si particles are converted into equiaxed, round pellets, spheres after solution at520℃8hours. The hardness of the alloy increased by20.5%, the friction coefficient and wear volume respective decrease by7.4%and 68.6%.