定向凝固多孔Mg-Zn合金的制备及气孔结构

采用Bridgman型定向凝固法制备出藕状多孔Mg-Zn合金。研究了不同锌含量和氢气压力对气孔形貌的影响。通过理论计算对Mg-1Zn(质量分数,%,下同)合金的孔隙率进行了预测。结果表明,锌元素的加入会对孔结构产生重大影响。随着Zn含量从0%增加到2%,平均孔径增加。随着氢气压力从0.1 MPa增加到0.6 MPa,Mg-1Zn合金的孔隙率明显降低。基于氢气在多组分熔融金属中溶解度的计算模型,Mg-1Zn合金铸锭凝固高度为20 mm的不同氢压孔隙率的计算结果与实验的结果比较吻合。通过组织观察表明,随着Zn含量的增加,凝固组织由柱状晶转变为等轴晶。此外,研究了在不同凝固阶段孔的形成过程,可为在生物医用材料中应用的定向凝固多孔Mg-Zn合金的制备提供理论依据。

Fabrication and pore structure of directionally solidified porous Mg-Zn alloy

Lotus-type porous Mg-Zn alloys were fabricated successfully by Bridgman-type directional solidification method. The pore structure and porosity of Mg alloys at different Zn content and hydrogen pressure were studied. The porosity of Mg-1wt.% Zn was predicted through the theoretical calculation. The results show that pore structure can be influenced by the addition of Zn element. As the content of Zn increases from 0 to 2 wt.%, average pore diameter increases. The porosity of Mg-1wt.%Zn alloy clearly decreases with the increasing of the hydrogen pressure from 0.1MPa to 0.6MPa. Based on a model for estimating the solubility of hydrogen in multi-component molten metals, the calculated results of porosity at the solidification stage (20mm height) with a changed hydrogen pressure in Mg-1wt.%Zn alloy, are in good agreement with the experimental results. Through observations on the microstructures, the column grains of Mg-Zn alloy are changed into equiaxed grains as the content of Zn increases. Also, the formation of pore at different solidification stages was studied, which can supply theoretical basis for the fabrication of Gasar Mg-Zn alloy in the biological applications.