规则多孔Cu-Cr合金的制备及其压缩特性

Fabrication and Compressive Properties of Ordered Porous Cu-Cr Alloys

采用金属-气体共晶定向凝固技术,在氢气压力为0.6 MPa,保温温度为1250℃的条件下制备出了直径为Ф100 mm,高度为170 mm的规则多孔Cu-xCr(x=0,0.3,0.8,1.3(%,质量分数))合金试样。结果表明,凝固高度对气孔率没有影响,但是随着凝固高度的增加,试样的平均气孔直径不断变大,这是因为随着固/液界面逐渐远离水冷结晶器,导致凝固界面的移动速率变慢。随着Cr含量的增加,试样的气孔率增大,而平均气孔直径先增大后减小,其原因是Cr的加入改变了凝固界面处固液二相区的宽度,导致基体与气孔的协同生长行为发生了相应的变化。规则多孔纯Cu及Cu-Cr合金的应力-应变曲线均由弹性变形阶段、屈服平台阶段以及密实化阶段3部分组成,由于Cr的加入能够显著提高金属基体强度,使得规则多孔Cu-Cr合金的压缩性能明显优于多孔纯Cu。与规则多孔纯Cu相比,多孔Cu-Cr合金的应力-应变曲线向上发生了偏移,且偏移量随着Cr含量的增加而增大,但是Cr的加入会使应力-应变曲线的密实化开始应变值变小,应力平台阶段的长度变短,从而导致多孔材料的吸收能降低。

Ordered porous Cu-xCr （x = 0, 0. 3, 0.8, 1.3 （ %, mass fraction） ） alloy castings （ diameter of 100 mm, height of 170 mm） were fabricated by metal-gas eutectic unidirectional solidification technique in a hydrogen atmosphere of 0. 6 MPa and holding temperature of 1250 ℃. The results showed that the solidification height had no influence on the porosity, but the average pore diameter became larger with solidification height increasing, which was because the solidification velocity decreased when the solidification interface moved away from the water cooling mold gradually. With the increase of Cr content, the porosity increased while the average pore diameter firstly increased and then decreased because of the change of the mushy zone width and the corresponding change of collaborative growth behavior of the solid matrix and gas pores. The compressive stress-train curves of the porous pure Cu and Cu-Cr alloy consisted of linear elastic stage, plateau stage and densification stage, owing to that the addition of Cr could effectively increase the matrix strength, and resulted in that the compressive properties of the ordered porous Cu-Cr alloys were obviously better than that of porous pure Cu. Compared with the ordered porous Cu, the stress-strain curve of the ordered porous Cu-Cr alloys moved upward with Cr contents increasing, and the offset increased with the increase of the contents of Cr; but the addition of the Cr had the effect of decreasing the densification strain and shortening the length of plateau stage, which led to the degradation of energy absorption ability.