Introduction of rare-earth element Sc in alloy design to modify wear features of dual-phase high-entropy alloy

Tailoring the alloy composition, which induces the hard secondary phase to increase hardness and strength to improve the wear features, is a feasible approach for developing wear-resistant metal materials. Here, a group of (AlCoCrFeNi)_100–xSc_x (x = 0–2.0, at%) high-entropy alloys (HEAs) are designed and the phase compositions and wear behaviors are explored. Sc-doped HEA series contain the primary body-centered cubic (BCC) and eutectic phases, in which the eutectic phase is composed of the alternately grown BCC and Laves phases. Sc addition promotes the diffusion of Ni atoms from BCC phase to form the Sc-rich Laves phase at the grain boundaries. Vickers hardness increases due to solid solution strengthening and second phase strengthening. And the second phase strengthening plays a more significant role relative to solid solution strengthening. Laves phase and the oxides caused by wear heating prevent the direct contact between friction pair and HEAs, thus inducing a decreased wear rate from 6.82 × 10⁻⁵ to 3.47 × 10⁻⁵ m³·N⁻¹·m⁻¹. Moreover, the wear mechanism changes from adhesive wear, abrasive wear and oxidative wear to abrasive wear and oxidative wear.