Effect Of Sm Element On The Microstructure And Properties Of Al-Mn-Si-Fe-Cu Fin Alloy

Al-Mn-Si-Fe-Cu alloy is a kind of heat-transfer material widely used in automotive radiators.It has the characteristics of small specific gravity,large specific strength and corrosion resistance.Rare earth elements is an effective additive,for grain refinement and enhancement of alloy strength.In this thesis,effect of Sm content on the microstructure,mechanical properties and electrochemical corrosion of simulated brazing or annealed Al-Mn-Si-Fe-Cu alloys was systematically studied.The main conclusions are as follows:?1?For the simulated brazing alloy,the addition of Sm element can refine the grain size.When the Sm content is 0.5%,the refining effect is the most remarkable.With further increase of Sm content,the refining effect will be weakened.The precipitated phase in the alloy is mainly Al₆?Mn,Fe?Si phase and the Sm-containing precipitates are Al₂Sm and Al₁₀Cu₇Sm₂.For a Sm content 0.5%,the precipitates are fine and spherical.The addition of Sm has a certain improvement on the mechanical properties.Compared to 0.3%and 0.8%Sm,the alloy with 0.5%Sm has a higher mechanical property.The fracture mechanism of the alloy is ductile fracture,with many dimples found in the fracture surface.The corrosion of the alloy in 0.5%NaCl and 3.5%NaCl solution is dominated by pitting corrosion.The corrosion potential of the precipitated phases is more negative than that of the Al matrix.The Al matrix around the precipitated phase is preferentially corroded to form pits.The addition of Sm element can make the precipitated phase of the alloy finely spherial and thus improve the corrosion resistance to a certain extent.When the Sm content increases from 0.3%to 0.5%,the corrosion potential of the alloy shifted positively and the corrosion resistance of the alloy is improved.When Sm content increases to 0.8%,corrosion potential greatly decreases.?2?After annealing,the second phase of the alloy is still mainly Al₆?Mn,Fe?Si phase,with a small amount of Sm-containing phase.In the alloy containing 0.5%Sm,the grain size and the second phase are relatively small,indicating that the addition of Sm can promote grain refinement.After annealing,the alloy was softened and overall mechanical properties decline.For three alloys,the grain size of 0.5%Sm alloy is the smallest,which leads to a better mechanical properties.Corrosion of three kinds of alloy is mainly pitting.Some of the larger second phases are found in alloys with 0.3%or 0.8%Sm.The Al matrix around the second phase could be corroded first,leaving larger and deeper corrosion pits.The corrosion potentials of these two alloys are relatively negative and the corrosion current density is also higher.?3?Among the three alloys,the alloy with 0.5%Sm has a better overall performance.And the grain structure is finer than the alloy with 0.3%and 0.8%of Sm addition.Among the three alloys,the alloy with 0.5%Sm addition amount of 0.5%has the best mechanical and electrochemical properties.