Copyright Max-Planck-Institut für Eisenfoschung GmbH

Design of high and medium entropy alloys with invar effect

In this project, we probe the invar effect in the high and medium entropy alloys over the huge unexplored compositional space. Combining experimental investigation (PPMS, EBSD, ECCI, APT and TEM) and theoretical calculation (DFT and Calphad), novel high and medium entropy invar alloys are being designed and the related fundamental mechanisms will be revealed.

After more than one hundred years of development, invar alloys are still not fully optimized in terms of other additional properties such as density, strengths and corrosion resistance. Recently, the discovery of high and medium entropy alloys provides a great chance for the optimization of invar alloys. The close-knit connection of magnetic properties and thermal expansion behavior suggests that promising invar alloys can be designed by tuning magnetic properties. Multifunctional high and medium entropy invar alloys are being achieved via theory-assisted alloy design over the huge compositional space.

Thermal expansion of an equiatomic FeNiCo medium entropy alloy. (a) Change in length as a function of temperature. (b) Thermal expansion coefficient α as a function of temperature. The thermal expansion coefficient α can be calculated as α= dL/(dT×L0), L is the sample length, T is the temperature, L0 is the sample length at room temperature.

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