Metals become softer when they are heated up, as their stiffness decreases due to thermally induced expansion. More than a decade ago, Swiss physicist Charles Edourad Guillaume, who received the Nobel Prize in Physics in 1920, discovered a nickel based alloy with temperature insensitive elastic modules, which he named Elinvar. Such Elinvar alloys are very rare and the underlying mechnisms are still under debate. Recently, a research team led by Prof. Yang Yong at CityU together with international collaborators has discoveried a super-elastic high-entropy alloy, which exhibits an extraordinary Elinvar effect, retaining near-constant elastic modulus from room temperature to more than 600 degree Celsius. Furthermore, normal metals unusally have the elastic strain limit less than one percent, except those having pseuado-elasticity associated with phase transformation and large energy dissipation. This newly discovered alloy can attain a high elastic strain limit of two percent. We performed in situ high energy x-ray diffraction studies which demonstrated that the high elastic strain limit is not related to stress-induced phase transformation, but rather arises from the high lattice friction. Such a novel alloy with unprecendented mechanical properties has a great potential for aerospace engineering.
Read more at Nature:
https://www.nature.com/articles/s41586-021-04309-1
The paper was featured in CityU Research Stories:
https://www.cityu.edu.hk/research/stories/2022/02/10/super-elastic-high-entropy-elinvar-alloy-discovered-potential-aerospace-engineering
09 Feb 2022