DC铸造5182铝合金大尺寸扁锭偏析及微观组织的试验研究

Experimental research on segregation and microstructure of 5182 large-sized slab cast by DC casting

为研究DC铸造Al-Mg合金大尺寸扁锭宏观偏析及微观组织分布特征,从而对后续探究偏析的形成以及改善偏析提供理论参考,本试验利用直读光谱仪(OES)、光学显微镜(OM)、扫描电镜(SEM)对5182铝合金宏观偏析、析出相及晶粒尺寸开展了试验研究。研究结果表明:沿5182铝合金铸锭横截面厚度方向,Mg元素呈中心负偏析、四分之一厚度区域正偏析趋势;Al6MnFe、Mg2Si为5182铝合金铸态组织主要析出相,另外包含少量Al2CuMg相,其中,Al6MnFe相含量沿铸锭中心至铸锭表面呈先增大后减小再增大的趋势,Mg2Si相在铸锭中心与四分之一厚度区域析出较多,其余位置的较少,Al2CuMg相仅少量存在于铸锭表面与中心区域。晶粒尺寸由铸锭表面至中心呈先增大后减小的趋势。

Optical emission spectrometer(OES), optical microscope(OM) and scanning electron microscope(SEM) were used to study macrosegregation, precipitation phase and grain size distribution of 5182 aluminum alloy in order to investigate segregation and microstructure characteristics in large-sized DC-cast Al-Mg alloy slab, so as to provide a theoretical basis for further research on the formation of segregation and reduction of segregation. The results show that in the thickness direction of the cross section, the Mg element shows a trend of negative segregation at centerline and positive segregation at 1/4 thickness;Al6MnFe and Mg2Si are the main precipitated phases in the as-cast structure of 5182 aluminum alloy,and there is a small amount of Al2CuMg, among them, the content of Al6MnFe phase from the center to the surface of slab increases first,decreases later and then increases.Mg2Si phase precipitates more in the center and the 1/4 thickness area,and fewer in other positions. Only a small amount of Al2CuMg phase exists on the surface and at center of the slab. The grain size increases from the surface to the center and then decreases.