<p>A lap butt welding process using AlCoCrFeNi_2.1 eutectic high entropy alloy as an intermediate layer was used to heterogeneously join 2&#xa0;mm thick Al/Steel. The mechanical characteristics of the joints and the intermetallic compounds (IMCs) layer were examined in relation to varying laser powers. The highest joint tensile load at 2100 W laser power is 1279 N, which is 82.3% greater than the joints maximum value at 1900 W laser power. To determine the causes of the impact of HEAs and laser power on the functionality of the welded joints, further thorough research was conducted. By EDS and XRD analysis of the welded joints. The results shows that slow diffusion effect of the high entropy alloy can successfully suppresses the formation of the IMCs in the weld within a certain range of parameter processes. When the laser power and the depth of fusion increases to a certain value, intermetallic compounds are observed in the weld, which leads to the internal cracking. Mechanical properties and dislocation strengthening mechanism of the joints were studied. It reveals that the increases in laser power increased the number of the low-angle grain boundaries and dislocations. In addition, the increase of the intermetallic compounds thickness at the interface and the increase of laser power was also effective in improving the homogeneity of the intermetallic compounds layer and strengthening the welded joint.</p> Graphical abstract <p></p>