Influence Of Alloy Elements In Alternating Magnetic-Field On Microstructures And Property Of Al-Mg₂Si Composite

This topic studied the impact on microstructure and mechanical properties ofMg₂Si/Al composite by changing magnetic induction intensity and mixing time of theelectromagnetic stirring and adding content compounds rare-earth elements of La,intermediate alloy of P-Cu, metal of Bi and heat treatment.It is found from the experimental results that electromagnetic stirring can improvemicrostructures and mechanical properties of Mg₂Si/Al composite to a certain extent. Oncondition that density of alternating magnetic-field is140G and stirring duration is60s,composite microstructures acquired is finer relatively, and mechanical properties hasimproved to some extent.Rare-earth elements of La, intermediate alloy of P-Cu, metal of Bi can improving themicrostructure and mechanical properties of Mg₂Si/Al composite in alternatingmagnetic-field or without alternating magnetic-field, an appropriate amount of alloyelements can significantly refine the grain of Mg₂Si, improve their shape and distribution,circle primary Mg₂Si to a certain extent, meanwhile, it could also inhibit the anisotropicgrowth of Mg₂Si phase in eutectic phase.The fining effect is best when input of rare-earthelement La is0.6%, alloy Bi is controlled at3%and P-Cu alloy is controlled at0.6%indifferent time, on this condition, primary Mg₂Si is finest, most regular and uniformlydistributed, the mechanical properties of composite are relative best.The effect of alloy elements on the mechanical properties of Mg₂Si/Al compositeswere discussed, the performance index-Tensile strength、elongation and hardness of thecomposite showed a trendency which increase first and then decrease with the increaseamount of alloy elements. As a whole, the refining effect of La is the best.The Mg₂Si/Al composite in electromagnetic stirring after heat-treatment, solidsolution plus aging heat treatment can reduce cast defects such as segregation and internalstress of Mg₂Si/Al composites, and improve the hardness and tensile strength of the composites by ensuring certain ductility. The optimized heat treatment process is found tobe545℃,5h solid solution plus175℃,3h aging. Under this process, the optimummicrostructure could be achieved with fine primary Mg₂Si phase and uniform, dispersedround-like eutectic Mg₂Si without lamellar Mg₂Si phase. The corresponding hardness andtensile strength increased by18.5%and18.4%respectively, with slight decrease ofelongation.