• Doping Co into AlNbTiVCr LHEAs transforms the microstructure from a single B2 phase to a dendritic mixture of B2, C14, and C15 Laves phases, with coupled growth of C14 and C15.
• Increasing Co content from 0 to 1.5 at.% raises the Laves phase volume fraction, boosting compressive strength from 1,520.8 MPa to 1,844.4 MPa and achieving a maximum Vickers hardness of 699.4 HV.
• The mechanical property enhancement is primarily attributed to solid solution strengthening and second phase strengthening from the Laves phases.
• The formation of B2 and Laves phases in these LHEAs can be predicted using parameters such as mixing enthalpy, valence electron concentration, atomic radius size, mixing entropy, and electronegativity difference.