Mechanism of improved wetting and spreading properties of Al-Si alloy/steel system by porous high entropy alloy

FeCoNiCrMn high entropy alloy powder was prepared by electrode induction melting gas atomizing method, and porous high-entropy alloy coatings with different porosities and pore diameters were prepared on the steel surface by vacuum sintering technique. The effects of different sintering processes on the porosity, pore size and transition layer thickness of the porous coatings were studied. In situ wetting and spreading tests of Al-12Si alloy on the surface of porous high-entropy coated steel were carried out to explore the influence of the porous high-entropy alloy coating on the apparent contact angle and spreading behavior, and the microstructure and phase composition of the reaction products within the porous high-entropy structure were analyzed in depth. The results show that with the increase of sintering temperature and the extension of holding time, the transition layer thickness of the porous high-entropy alloy coating gradually increases, and the porosity and average pore size gradually decrease. Liquid Al-12Si alloy droplets rapidly infiltrated into the porous structure and achieved complete wetting of the material surface under the action of capillary forces enhanced by microchannels in the porous coating. The formation of intermetallic compounds in the interfacial reaction layer is significantly hindered by the combined effect of hysteresis diffusion and high entropy of the high-entropy alloy, and the interfacial phase structure consists of Cr-rich FCC, AlFe-rich BCC, and AlNi-rich B2+Al-rich BCC eutectic structures.