Effect of High-Intensity Pulsed Ion Beam Irradiation on the Mechanical Properties and Microstructure of the AlCoCrFeNi High-Entropy Alloy

Abstract The effect of high-intensity pulsed ion beam (HIPIB) irradiation on the microstructure and surface properties of equimolar AlCoCrFeNi high-entropy alloy has been investigated at two energy densities, 0.7 and 1.5 J/cm 2 . Finite element simulation of the thermal field shows that both regimes produce surface melting with peak temperatures of 2596 K and 3206 K, maximum melt depths of 0.45 and 0.93 µm, and cooling rates of the order of 10 10 K/s. XRD analysis reveals that the dual-phase BCC + FCC microstructure of the as-cast alloy transforms into a predominantly BCC structure after irradiation, with the complete disappearance of the FCC (111) reflection. Energy-dispersive spectroscopy confirms compositional homogenisation of the near-surface layer. The structural changes result in a non-monotonic dependence of mechanical properties on energy density. Irradiation at 0.7 J/cm 2 increases Vickers hardness by 30%, from 648 ± 52 HV 0.05 to 839 ± 68 HV 0.05 , and reduces the specific wear rate from 2.94×10 − 4 to 8.42×10 − 5 mm 3 ·N − 1 ·m − 1 , while at 1.5 J/cm 2 both hardness and wear resistance approach the as-cast values. The results demonstrate that HIPIB irradiation is an effective tool for surface modification of high-entropy alloys, enabling phase transformation and significant tribological improvement.