Mn、Fe含量对3003铝合金铸锭均匀化行为的影响

Effect of Fe and Mn Content on the Homogenization Behavior of DC-cast 3003 Alloy

通过电导率测试、扫描电子显微镜等观察分析,研究了不同Mn、Fe含量对3003合金铸锭和均匀化组织的影响。3003合金铸锭中有明显的波纹状Mn偏析,晶界处有粗大的α-Al(Fe,Mn)Si或Al_6(Fe,Mn)初生相。Fe含量由0.12%(质量分数)升高至0.30%,铸锭平均晶粒尺寸由257μm减小为108μm,初生相面积分数由1.28%升高至3.75%;Mn含量越高,合金电导率值越低。均匀化升温阶段,析出相主要受形核和长大过程控制,并伴随较高温度下析出相的部分回溶;600℃保温阶段,析出相以Ostwald熟化和原子长程扩散两种机制发生粗化,尺寸不断增大,数量减少;合金均匀化晶界附近有无析出带形成。合金Mn含量由1.15%升高至1.60%,析出相回溶温度由500℃升高至550℃,600℃保温12h完成后,析出相尺寸也由149.0nm升高至342.5nm;高Fe低Mn(0.30%Fe,1.15%Mn)合金晶内析出相分布均匀,而低Fe高Mn(0.12%Fe,1.60%Mn)合金晶内析出相呈不均匀分布,晶粒心部及枝晶干处贫Mn区析出相数量较少。

The ingot and homogenization microstructure of 3003 with various Mn, Fe content were investigated by electrical conductivity measurement and scanning electron microscopy. There were obvious Mn concentration in 3003 ingot and coarse primary particles, like α-Al（Fe,Mn）Si or Al 6（Fe,Mn）, around grain boundaries. When the Fe content of alloy increased from 0.12% （mass fraction） to 0.3%, the average grain size decreased from 257 μm to 108 μm, and the area fraction of primary particles rose from 1.28% to 3.75%. The alloy with higher Mn content exhibited lower electrical conductivity. During homogeneous heating stage, precipitation phase is mainly controlled by nucleation and growth process, which could be partially dissolved at higher temperature. During homogenization at 600 ℃, the precipitates were coarsened by Ostwald ripening process and long distance diffusion of manganese with enlargement in sized and reduction in quantity. There was precipitation free zone formed near the grain boundary during homogenization. With the increase of Mn content from 1.15% to 1.6%, the dissolution temperature of precipitates rose from 500 ℃ to 550 ℃. After 600 ℃ heat preservation for 12 h, a size increase from 149.0 nm to 342.5 nm of precipitates could be observed. The alloy with high Fe content and low Mn content （0.3% Fe, 1.15% Mn） showed uniform precipitation distribution in grains, while the alloy with low Fe content and high Mn content （0.12% Fe, 1.6% Mn） featured nonuniform precipitation distribution in grains. And there was small amount of precipitation in Mn-depleted areas like grain core and dendrite trunk.