Zr含量对Al-Zr合金时效析出和性能的影响

对比研究了Zr添加(0.05,0.15和0.25wt%)对Al-Zr合金固溶态和固溶轧制态时效析出行为、硬度和导电率的影响。结果表明,固溶态Al-Zr合金的晶粒尺寸随Zr含量的增加而减小,但是固溶轧制态Al-Zr合金的晶粒尺寸对Zr添加量不敏感。固溶态Al-Zr合金在350 ℃时效过程中,由于Al₃Zr沉淀相的析出,合金硬度随Zr含量增大而增大,但是更强的点阵畸变场则导致导电率降低。而在固溶轧制态合金的时效中,大量变形位错的存在促进了Al₃Zr相的析出,Al-Zr合金在250 ℃下时效具有比350 ℃时效更优的硬度和导电率的综合性能。特别是0.25wt%Zr添加的Al-Zr合金,其析出强化可以有效补偿时效过程中位错湮灭引起的硬度降低,保持较高的硬度。综合考虑,固溶轧制态Al-0.25wt%Zr合金经250 ℃时效25 h后具有最优的硬度(47.5 HV0.5)和导电率(55.6%IACS)组合。

Effect of Zr content on aging precipitation and properties of Al-Zr alloy

Effects of Zr addition (0.05, 0.15 and 0.25wt%) on precipitation, hardness, electrical conductivity of solution-treated and solution-rolled Al-Zr alloys were compared and studied. The results show that the grain size of solution-treated Al-Zr alloys deceases with the increase of Zr content, but the grain size of solution-rolled alloys is insensitive to the Zr addition. Due to the precipitation of Al₃Zr particles in the aging process at 350 ℃, the hardness of solution-treated Al-Zr alloys increases with the increase of Zr content. However, stronger lattice distortion field leads to the decrease of electrical conductivity. During the aging of solution-rolled Al-Zr alloys, a large number of deformation dislocations promote precipitation of the Al₃Zr phase, which makes the Al-Zr alloys aged at 250 ℃ to have better combined properties of hardness and conductivity than that aged at 300 ℃. Especially, with the addition of 0.25wt%Zr in the Al-Zr alloys, the precipitation strengthening during aging can effectively compensate the hardness lowering caused by dislocation annihilation, so that the high hardness of the alloys is maintained. Overall, the optimal combined properties of hardness and conductivity of 47.5 HV0.05 and 55.6%IACS can be obtained by the solution-rolled Al-0.25wt%Zr alloys aged at 250 ℃ for 25 h.