Interfacial microstructure and strengthening mechanism of dissimilar laser al/steel joint via a porous high entropy alloy coating

A porous high entropy alloy (HEA) coating was prepared on a steel surface by vacuum sintering. The then used as transition layer during dissimilar laser joining of Al to steel. Compared with the uncoated joints, liquid spread and infiltrated into structure, contact angle weld reduced from 65.8° 56.7°, brazed width increased 5.1 mm 5.9 mm, which improved wettability spreadability molten filler wire substrate. In case steel, fusion zone/steel interfacial microstructure consisted laminated Al7·2Fe1·8Si Fe(Al,Si)3, while it changed composite-like structure containing soft HEA skeleton hard IMCs included Al7·2Fe1·8Si, Al3Ni, (Al,Si)2Cr. addition, due sluggish diffusion effect HEAs, gradient nanocrystalline composed generated, significantly strengthened joints improvements in both fracture load (∼26.5%) displacement (∼101.8%). mode brittle ductile failure when applied, propagating through skeleton. This work provides novel solution for strengthening hard-to-join combinations.