Thermodynamic properties of Co-based high-entropy alloys CoCrAlSi & CoVGaGe.

Materials by design is the principle of designing technological materials (e.g. vibrational energy harvesting) through first-principle simulations, rather than attempting to fabricate and test every possible candidate material. In order to confirm a model’s accuracy, it is essential to compare such atomistic simulations against measurements. The materials studied in this work were the Co-based shape memory alloys CoCrAlSi & CoVGaGe. These alloys exhibit a reentrant martensitic transformation around 400 K, and the elastic constants of these materials show a minimum near 20 deg C for reasons not understood at this time. We present herein inelastic neutron scattering measurements of powder samples of Co-based high-entropy alloys CoCrAlSi & CoVGaGe. The neutron scattering data was collected at J-PARC on BL01-4Seasons over the temperature range 100 K to 450 K. We have corrected the data for multiphonon and multiple scattering effects. The resulting neutron-weighted density of states shows a decrease in the energy of the low-energy van Hove singularity in CoCrAlSi with increasing temperature, and in CoVGaGe a complete disappearance of a van Hove singularity at 430 K. Future work will involve first principle calculations of the phonon spectrum to determine the contribution of neutron cross-section weighting to the measured density of states.