Statistical mechanics, entropy and temperature analog of dislocations moving on fluctuating resistance landscapes

Abstract

High/medium-entropy alloys, also known as complex concentrated alloys (CCAs), are so called because the mixing entropy reaches a maximum when the constituent multi-elements adopt equiatomic ratios. However, the mixing entropy relates little to mechanical strength for which these alloys are most studied. By analyzing dislocations in VCoNi via electron microscopy and molecular-dynamics from a machine interatomic potential, their energies are found to obey a maximum-entropy distribution in the random alloy state, but not in the annealed state where local chemical order (LCO) exists. The maximum-entropy distribution is characterized by an athermal, mechanical analog of temperature which relates directly to the alloy strength and dominates over the real temperature over a wide range. The entropy of dislocations is a fingerprint of LCO, and statistical mechanics is an impeccable theoretical framework for understanding dislocations and strength in CCAs.