硅、镍含量与制备工艺对Al-Si-Ni合金组织和热学性能的影响

Effects of Si and Ni Content and Preparation Process on Microstructure and Thermal Properties of Al-Si-Ni Alloy

利用普通凝固、水冷铜模亚快速凝固和水冷铜模亚快速凝固复合热处理(520℃×6 h)3种工艺,分别制备了Al-11Si-5Ni合金、Al-22Si-10Ni合金和Al-33Si-15Ni合金,研究了不同合金的显微组织和热学性能。结果表明:Al-11Si-5Ni共晶合金在凝固过程中仅发生Al-Si-Al_(3)Ni三元共晶反应,形成由α-Al相、共晶硅相和共晶Al_(3)N相组成的三元共晶组织;Al-22Si-10Ni合金与Al-33Si-15Ni合金为过共晶合金,组织由初生硅相、初生Al_(3)N相和三元共晶组织组成,其凝固过程分为初生硅相析出、初生硅相与Al_(3)Ni相的共同析出以及Al-Si-Al_(3)Ni三元共晶反应3个阶段;随着镍、硅含量的同步增加,初生硅相与Al_(3)Ni相粗化;与普通凝固工艺相比,水冷铜模亚快速凝固工艺可以细化合金组织,而热处理使共晶硅相与共晶Al_(3)Ni相发生球化。随着硅、镍含量的同步增加,合金的热导率与热膨胀系数均下降,而水冷铜模亚快速凝固复合热处理可以有效提升合金的热导率。水冷铜模亚快速凝固复合热处理工艺制备的Al-22Si-10Ni合金具有优异的综合性能,其室温热导率为129.9 W·m^(-1)·K^(-1),100℃热膨胀系数为13.8×10^(-6) K^(-1),25~100℃平均热膨胀系数为12.9×10^(-6) K^(-1)。

Three kinds of alloys,Al-11Si-5Ni,Al-22Si-10Ni and Al-33Si-15Ni,were prepared by ordinary solidification,water-cooled copper mold sub-rapid solidification and water-cooled copper mold sub-rapid solidification combined with heat treatment(520℃×6 h).The microstructures and thermal properties of the alloys were studied.The results show that only Al-Si-Al_(3)Ni ternary eutectic reaction occurred in the solidification process of Al-11Si-5Ni eutectic alloy,and the microstructure was ternary eutectic structure composed ofα-Al,eutectic silicon and eutectic Al_(3)N phases.The Al-22Si-10Ni and Al-33Si-15Ni alloys were hypereutectic alloys,the microstructure consisted of primary silicor phase,primary Al_(3)Ni phase and ternary eutectic structure,and the solidification process was divided into three stages:the primary silicon phase precipitation,the primary silicon and Al_(3)Ni phase co-precipitation,and Al-Si-Al_(3)Ni ternary eutectic reaction.With the simultaneous increase of Ni and Si content,primary silicon and Al_(3)Ni phases were coarsened.Compared with the ordinary solidification process,the water-cooled copper mold sub-rapid solidification process could refine the alloy structure,and the heat treatment made the eutectic silicon phase and the eutectic Al_(3)Ni phase spheroidize.With the simultaneous increase of the content of Ni and Si,the alloy's thermal conductivity and the thermal expansion coefficient decreased.The water-cooled copper mold sub-rapid solidification combined with heat treatment could effectively improve the thermal conductivity of the alloy.Al-22Si-10Ni alloy prepared by the water-cooled copper mold subrapid solidification combined with heat treatment had the best comprehensive performance with the room temperature thermal conductivity of 129.9 W·m^(-1)·K^(-1),the thermal expansion coefficient at 100℃of 13.8×10^(-6) K^(-1),and the average thermal expansion coefficient in the temperature range of 25‒100℃of 12.9×10^(-6) K^(-1).