Variations in mechanical, electrical, thermal properties, and residual stress of laser powder bed fused Al–Fe binary alloy by annealing

Al–2.5 mass% Fe binary alloys were prepared by laser powder bed fusion (L-PBF), and the effects of annealing below 573 K on the electrical, mechanical, thermal properties, microstructure, and residual stress were investigated. The electrical resistivity of the L-PBF alloy remained almost unchanged after annealing at 473 K, while that of the specimen annealed at 573 K decreased from 20 to 8 nΩ m and from 47 to 37 nΩ m at 77 K and 293 K, respectively. Vickers hardness (measured on the surface normal to the building direction) increased to about 102 HV from 97 HV, then decreased to 94 HV during annealing at 573 K, showing a similar trend on the parallel surface. These hardness changes agreed with the formation of nanoscale Al 6 Fe precipitates, corresponding to a decrease in solute Fe concentration of about 0.47–0.52 mass% estimated from electrical resistivity and X-ray diffraction. Compression tests revealed no anisotropy in the 0.2 % proof stress between as-built and annealed specimens. Residual stress was effectively removed by annealing at 573 K for >120 s. Annealing also increased the specific heat from 800 to 920 J/(kg·K), attributed to reduced solute Fe and an increased Al 6 Fe fraction. The measured thermal conductivities agreed well with reported values.