Influence of Mn on microstructure of as-cast and homogenized 6082 aluminum alloy
Microstructure and precipitation behavior of as-cast and homogenized 6082 aluminum alloy with Mn content of 0.7 mass％ and 0.5 mass％(named 07Mn alloy and 05Mn alloy,respectively)were studied by means of optical microscope(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM),differential scanning calorimetry(DSC)and conductivity tester.The results show that coarser fishbone-like crystalline phases are formed in the microstructure of the as-cast 07Mn alloy.After homogenization annealing,the insoluble crystalline phases at the grain boundaries are transformed into micrometer sized α-Al(Mn,Fe)Si phase,and nanoscale α-Al(Mn,Fe)Si phase is precipitated in the grain.The precipitation activation energy of α-Al(Mn,Fe)Si phase in the 07Mn alloy is lower,resulting in the precipitation of more and smaller α-Al(Mn,Fe)Si phase.Through conductivity calculation,it is confirmed that Mn element promotes the nucleation of α-Al(Mn,Fe)Si phase in the alloy.
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