Al-7.5Ni-xFe合金的组织演变与热物性能  

Microstructure evolution and thermal properties of Al-7.5Ni-xFe alloy

作　　者：江民浩 莫丽玲 杜军[1] JIANG Min-hao;MO Li-ling;DU Jun(School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,China)

机构地区：[1]华南理工大学材料科学与工程学院,广州510640

出　　处：《中国有色金属学报》2023年第9期2801-2812,共12页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金资助项目(52174363)。

摘　　要：利用普通铸造法制备了Al-7.5Ni-xFe(x=0,1,2,5,7)合金,采用光学显微镜、SEM-EDS和XRD等手段观测其组织特征,并测试导热率和热膨胀系数,揭示组织演变机制,讨论组织与热物性能之间的关系。结果表明:Fe加入后,合金的组织特征改变,由(α(Al)+Al_(3)Ni)共晶组织转变为Al_(9)Fe_(2-y)Ni_(y)相和α(Al)组成的混合组织。随Fe含量增大,Al_(9)Fe_(2-y)Ni_(y)相中Fe/Ni比(摩尔比)逐渐增加并趋于等比,Al_(9)Fe_(2-y)Ni_(y)相逐渐粗化且体积分数增加,其形态由针状向板状转变,并呈现定向排列特征。Fe含量增至7%后有星状Al_(13)Fe_(4)相析出,并在其表面由Al_(9)Fe_(2-y)Ni_(y)包覆。Fe加入后,合金的凝固进程发生变化,存在初生相析出、共晶进程缩短甚至产生分段共晶。Al_(9)Fe_(2-y)Ni_(y)由反应L+Al_(13)Fe_(4)→Al_(9)Fe_(2-y)Ni_(y)生成,分段共晶反应包括L+Al_(13)Fe_(4)→α(Al)+Al_(9)FeNi和L→Al_(3)Ni+α(Al)+Al_(9)FeNi。随Fe含量增加,热膨胀系数逐渐降低同时导热也逐渐恶化。利用有效介质模型(GEMT)可有效预测其导热系数,模型特征参数k_(0)最优值为38。通过Turner模型预测的合金热膨胀系数与实验值具有较大偏差,且共晶组织体积分数越大,偏差越显著;将共晶组织视为整体相对Turner模型进行修正,修正模型预测值与实验值吻合较好。The Al-7.5Ni-xFe(x=0,1,2,5,7)alloys were prepared by ordinary casting method,their characteristics of microstructures were observed by means of light microscopy,SEM-EDS,and XRD,etc,the thermal conductivity and thermal expansion coefficient were tested.The mechanism of microstructure evolution was revealed,and the relationship between microstructure and thermal properties was discussed.The results show that the microstructures of the Al-7.5Ni-xFe alloys are changed from(α(Al)+Al_(3)Ni)eutectic to a mixed microstructure composed of Al_(9)Fe_(2−y)Ni_(y)andα(Al)phase after Fe addition.With the increase of Fe content,the Fe/Ni ratio(mole ratio)in the Al_(9)Fe_(2−y)Ni_(y)phase gradually increases and tends to be isometric,along with the size coarsening and the volume fraction increasing.The morphology of Al_(9)Fe_(2−y)Ni_(y)changes from needle-like to plate-like,and shows the characteristics of directional arrangement.Al_(9)Fe_(2−y)Ni_(y)is generated by the reaction L+Al_(13)Fe_(4)→Al_(9)Fe_(2−y)Ni_(y)and the subsequent segmental eutectic reactions include L+Al_(13)Fe_(4)→α(Al)+Al_(9)FeNi and L→Al_(3)Ni+α(Al)+Al_(9)FeNi occurred when the Fe content is high.The thermal conductivity can be effectively predicted by the general effective medium model(GEMT),and the optimal value of the model characteristic parameter k_(0) is 38.The coefficient of thermal expansion predicted by the Turner model has a large deviation from the experimental value,and the larger the volume fraction of eutectic microstructure is,the more significant the deviation is.The eutectic microstructure is considered as a whole relative to the Turner model for modification,and the predicted value of the revised model fits well with the experimental value.

关 键 词：Al-Fe-Ni合金 导热系数 热膨胀系数 量化分析 

分 类 号：TG146.2[一般工业技术—材料科学与工程]