Microstructure evolution and thermal properties of Al-5%Fe-xNi alloys

Abstract

Al-5%Fe-xNi alloys （x=0%，1.5%，5%，7.5%，10%， mass fraction，the same below） were prepared by the traditional casting method， and the morphology and size changes of the primary phase in the alloys after Ni addition were observed. The transformation of the solidification process of the alloys and the effect of Ni addition on the primary phase and eutectic structure were analyzed， and the influence of Ni content on the microstructure and thermal properties of the alloys was discussed. The results show that with the increase of Ni content， the primary phase changes from irregular bulk to needle-like. As the Ni content exceeds 5%， the eutectic structure decreases， and the primary phase changes to a regularly arranged Al9FeNi phase. The addition of Ni significantly changes the solidification process of the alloys， resulting in the precipitation reaction of the primary phase from L→Al13Fe4 to L→Al9FeNi or L+Al13Fe4→Al9FeNi， and the eutectic precipitation reaction from L→α-Al+Al13Fe4 to L+Al13Fe4→α-Al+Al9FeNi and L→Al3Ni+α-Al+Al9FeNi. With the increase of Ni content， the volume fraction of the precipitated phase increases， and the thermal conductivity and thermal expansion coefficient of the alloys decrease. The thermal expansion coefficient of the alloys decreases from 19.9×10-6 K-1 （@25-200 ℃） of Al-5%Fe to 17.6×10-6 K-1 （@25-200 ℃） of Al-5%Fe-10%Ni. The thermal conductivity and thermal expansion coefficient of the alloys are predicted by using the general effective medium theory （GEMT） model and the modified Turner model， respectively. It is found that the simulated values are in good agreement with the experimental values.

Keywords

• al-fe-ni alloy
• microstructure evolution
• thermal conductivity
• thermal expansion
• quantitative analysis