Microstructure Evolution and Thermophysical Properties of Hypereutectic Al-Fe-Ni Alloys.

Hypereutectic Al-x(1.75Fe-1.25Ni) (x=1,2,4,6) alloys were designed and prepared by gravity casting in the present study. Both the microstructure and the thermophysical properties were investigated. The microstructure was significantly transformed from the eutectic phases to the coarse primary phases with the increase in alloying elements. The result of thermal analysis indicated that the solidification behaviors were modified by the increase in alloying elements, which was ascribed to the generation of different phases. The thermal conductivity and thermal expansion properties were also related to the alloy composition. From the variation in the ratio of thermal conductivity/electrical conductivity, it could be inferred the effective medium of heat conduction was changing, which decreased thermal conductivity due to the introduced defects that hindered the transport of electrons and low efficiency heat conducting medium of intermetallic. Meantime, the formation of bulk intermetallic with low thermal expansion coefficient and large volume fractions reduced effectively the thermal expansion of the alloy. The mathematical model was presented to quantify the influence of alloy content on thermophysical properties. [ABSTRACT FROM AUTHOR]