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在含1.0%Fe(质量分数)的A356铝合金中加入1.2%Mn(质量分数),经850℃熔化后降至615~680℃保温1 h。采用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)等现代研究手段研究保温温度对富铁相形态特征的影响规律,并探讨富铁相的形成机制。研究结果表明:随着保温温度的降低,合金组织细化效果逐步提升,富铁相分布均匀性增加;富铁相形态随温度降低的演变顺序为:星型+细网状→多边形(4~6)+汉字状→多边形(3~4)+汉字状+细网状→多边形(细小)+汉字状→汉字状;富铁相中的(Mn,Fe)/Si原子分数比值主要取决于富铁相的形态,而富铁相中Mn/Fe原子分数比主要取决于保温温度;统计数据发现,较低温度保温能有效降低富铁相的含量和细化富铁相尺寸,降低幅度分别达到62.6%和42.1%,而其余富铁相则以粗大的、圆整度高的多边形富铁相沉降在炉底。
1.2% Mn (mass fraction) was added into A356 aluminum alloy containing 1.0% Fe (mass fraction), melted at 850 ℃ and then cooled to 615-680 ℃ for 1 h. The effects of soaking temperature on the morphologies of the iron-rich phase were investigated by OM, SEM and EDS, and the formation mechanism of the iron-rich phase was also discussed. The results show that the refinement effect of the alloy gradually increases and the distribution of iron-rich phase increases with the decreasing of the holding temperature. The evolution order of the iron-rich phase with temperature decreases from star to fine mesh to polygon (4 ~ 6) + Chinese characters → polygons (3 ~ 4) + Chinese characters + fine mesh → polygon (small) + Chinese characters → Chinese characters; (Mn, Fe) / Si atomic ratio of iron rich phase mainly depends on the rich Iron phase morphology, while the rich iron phase Mn / Fe atomic fraction mainly depends on the holding temperature; statistics show that lower temperature insulation can effectively reduce the iron-rich phase content and refine the iron-rich phase size, the reduction rate reached 62.6% and 42.1% respectively, whereas the remaining iron-rich phases settle to the hearth with coarse, round, polygonal iron-rich phases.