Study On Microstructure And Properties Of Aluminum-silicon Alloys By Continuous Extrusion Of Atomized Powder

While emphasizing sustainable development,energy saving and emission reduction is an important measure.One of the effective ways is to use lightweight materials such as aluminum alloys and magnesium alloys to replace steel,and aluminum is the first metal element in the earth's crust At the same time,among the industrial metals,the metal with the highest recovery and recycling rate is aluminum.Therefore,aluminum alloys have broad application prospects.Combined with powder metallurgy and continuous extrusion technology,Al-x Si(x =11.65,28.5wt.%)and Al-28.5Si with different particle sizes(powder particle size greater than 75?m,75 ? 45?m,45 ? 25?m,Less than 25?m)of several aluminum-silicon alloys were prepared.Optical microscopy(OM),scanning electron microscopy(SEM),AG-X 100 k N electronic universal tensile testing machine,electronic backscatter diffraction system(EBSD)and other testing equipment and systems are used to study on microstructure and mechanical Properties of the powder continuous extrusion Al-x Si Alloy.Studies have shown that the phase composition of powder blanks includes ?-Al matrix,primary crystal Si,and acicular eutectic Si.After continuous extrusion,the needle eutectic Si disappear.The Si particles in the alloy structure are significantly refined,the shape is more regular and round,and it is evenly distributed in the aluminum matrix.The properties of Al-x Si alloy fabricated by continuous extrusion of atomised powders gradually increases the tensile strength with increasing Si content,but the plasticity decreases.When the Si content increased from 0% to 11.65% and 28.5%,the tensile strength increased from 98 MPa to 223 MPa and 248 MPa.The Si content increased from 11.65% to 28%,and the tensile strength increased by 25 MPa.The reason for the insignificant increase is considered to be that the size difference of the Al-28.5Si alloy powder is large,and that the Al-11.65 Si alloy powder has no uniform roundness.The morphology of the rapidly solidified Al-28.5 Si alloy powder is related to the cooling rate.The particle cooling rate is large,and the solidification shrinkage of the droplet is small.The rapid solidification of the droplet is easy to form small particles with smooth spherical surfaces.On the contrary,the surface of the cured droplets rougher.With the decrease of the powder particle size,the alloy powder changes from rod-like irregular shapes to near-spherical shapes,the powder surface is smooth,and burrs,pits and satellite particles attached to the particle surface are significantly reduced.The tensile strength and elongation at break of the Al-28.5Si alloy prepared by continuous extrusion of powders increase with the decrease of the particle size of the powder billet.When the powder particle size is reduced from more than 75 ?m to less than 25 ?m,the tensile strength of Al-28.5Si alloy increases from 211 MPa to 266 MPa,and the elongation at break increases from 0.99% to 2.21%.The Al-28.5Si alloy fabricated by continuous extrusion of atomised powders can obtain fine-sized aluminum grains,the grain size of aluminum is mainly concentrated between 0.75 to 2.25 ?m,and the average grain size of Si is less than 5 ?m.As the particle size of the powder decreases,the grain size gradually decreases after continuous extrusion.The Schmid factor increases as the particle size of the powder decreases.The internal dislocation activity of the deformed aluminum grains is higher,which is conducive to the occurrence of crystal slip in the sliding system.The plasticity of the Al-28.5Si alloy increases with The reduction of powder particle size tends to increase.The degree of recrystallization is large during the continuous extrusion of the powder,most of the energy is released during the recrystallization process,and the dislocations inside the recrystal grains are dispersed and the activity is not high.