Selective Laser Melting of an Al-Fe-V-Si Alloy: Microstructural Evolution and Thermal Stability

Selective laser melting was used to produce an aluminum alloy Al-8.5Fe-1.3V-1.7Si (wt%). The effects of heat treatment on microstructure evolution and phase stability during long-term thermal exposure of the deposits were investigated. Results show that the microquasi-crystalline phase, Al-12(Fe, V)(3)Si and AlmFe metastable phases coexisted with alpha-Al in the as-produced alloy. Annealing at 400 degrees C resulted in decomposition of microquasi-crystalline phase and supersaturated a-Al into Al-12(Fe, V)(3)Si phase in the fusion zone, accompanied by the decrease in alloy hardness. The activation energy of this decomposition process was 115 kJ/mol. A more homogenous microstructure was obtained after annealing at 400 degrees C for 60 min, which was resistant to coarsening exposed at 425 degrees C up to 500h. The Al-12(Fe, V) 3Si and AlmFe phases were coarsened at 475 and 525 degrees C with increasing the exposure time. Coarsening of Al-12(Fe, V) 3Si phase was attributed to a combination of volume diffusion and grain boundary diffusion mechanism of Fe. Heat treatment at 600 degrees C resulted in accelerated microstructure coarsening and formation of large-sized equilibrium phases, which significantly degraded the room temperature microhardness. Copyright (C) 2017, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited.