Effect of Heat Dissipation Rate on Microstructure and Mechanical Properties of Al0.5FeCoCrNi High-Entropy Alloy Wall Fabricated by Laser Melting Deposition

High-entropy alloys (HEAs) are a new type of multi-component alloy. The design of the compositions breaks the design ideas of traditional alloys and shows many excellent properties. Therefore, an Al0.5FeCoCrNi HEA with face-centered cubic (FCC) and body-centered cubic (BCC) dual-phase structure was used in this paper. During the additive manufacturing process, the heat dissipation rate gradually changes with the increase in wall height. As a result, the composition of the phases changes, resulting in differences in mechanical properties. Here, we designed laser melting deposition (LMD) on T-beams of different heights to change the heat dissipation rate of the wall, and the effects of the heat dissipation rate on the microstructure and mechanical properties of Al0.5FeCoCrNi HEAs were studied. The experimental results showed that increasing the height of the T-beam would gradually slow down the heat dissipation rate of the wall. The above phenomena not only led to a gradual reduction of the BCC phase under the influence of heat accumulation but also increased the length of columnar crystals in the wall with the slowing of heat dissipation. Heat accumulation hindered the nucleation during solidification and eventually led to the growth of grains across the deposition layer. Furthermore, the slow heat dissipation rate changed the grain number and BCC phase content, which gradually decreased the strength and hardness, while the ductility of the samples improved.