Evaluation of Microstructure and Hardness of Novel Al-Fe-Ni Alloys with High Thermal Stability for Laser Additive Manufacturing

Abstract : The microstructure and phase composition of cast and laser-melted Al-Fe-Ni alloys were investigated. Two main phases—Al3(Ni,Fe) and Al9FeNi—were formed in the as-cast state. A fine microstructure without porosity or solidification cracks was observed in the Al-Fe-Ni alloys after laser treatment. The hardness of the laser-melted alloys was 2.5–3 times higher than the hardness of the as-cast alloys owing to the formation of an aluminum-based solid solution and fine eutectic particles. The formation of the primary Al9FeNi phase was suppressed as a result of the high cooling rate. Annealing these alloys at temperatures less than 300°C demonstrated the high thermal stability of the microstructure while maintaining the hardness. The Al-Fe-Ni alloys investigated in this study are promising heat-resistant materials for additive manufacturing because of their fine, stable structure, and the low interdiffusion coefficients of Fe and Ni.