热处理对Al-Si-Mg-3%Cr合金微观组织与力学性能及耐腐蚀性能的影响

Effects of Heat Treatment on Microstructure,Mechanical Properties and Corros Resistance of Al-Si-Mg-3%Cr Alloy

采用真空电磁感应熔炼炉制备了Al-Si-Mg-3%Cr合金。利用Thermo-Calc软件进行热力学模拟,使用SEM、EDS等测试方法,表征了不同热处理状态下合金的微观组织,并测试其力学性能。采用失重法和电化学法测试其腐蚀性能。结果表明:合金主要物相包括α-Al、共晶Si、(Al+Si)共晶、富Cr相(Al13Cr4Si4、β-Al(Cr,Fe)Si)、富Fe相(β-Al5FeSi和π-AlSiMgFe)和Mg2Si。热处理后的合金组织中,共晶Si尺寸变小且球化,共晶组织区域变窄,细小的Al13Cr4Si4、β-Al(Cr,Fe)Si相弥散分布于共晶Si周围,这对改善热处理后合金的力学性能具有积极作用。腐蚀测试结果显示:相比于铸态合金而言,热处理后合金的平均腐蚀速率降低、极化曲线存在明显的钝化区、阻抗中容抗弧变大,表明热处理能够提高合金的耐腐蚀性能。其中T6态(535℃/6 h+160℃/26 h)合金的力学性能及耐腐蚀性最佳。

Al-Si-Mg-3%Cr alloy was prepared with vacum electromagnetic induction melting furnace.Thermo-Calc software was used to perform thermodynamic simulation.The microstructure of the alloy under different heat treatment conditions were characterized by SEM,EDS,and other test methods and its mechanical properties were tested.The corrosion resistance of the alloy was tested by mass loss method and electrochemical method.The results show that the main phases of the Al-Si-Mg-3%Cr alloy includeα-Al,eutectic Si,(Al+Si)eutectic,Cr rich phase(Ali3Cr4Si4,β-Al(Cr,Fe)Si),Fe rich phase(βB-AlsFeSi andπ-AISiMgFe)and Mg2Si.In the structure of heat-treated alloy,the eutectic Si becomes smaller in size and spheroidized in form,the zone of eutectic structure becomes narrow,and the fine Ali3Cr4Si4 andβ-Al(Cr,Fe)Si phase are dispersed around eutectic Si.All play positive roles in improving the mechanical properties of the alloy after heat treatment.The corrosion test results show that compared with the case of the as-cast alloy,the average corrosion rate of the heat-treated alloy decreases,an obvious passivation zone exists in the polarization curve,and the capacitive arc in impedance becomes larger.It is indicated that heat treatment can improve the corrosion resistance of the alloy,especially T6 process(535°C/6 h+160°C/26 h)can lead to the optimum mechanical properties and corrosion resistance.