Martensite as a Key to Unlock the Ideal Strength in Solids

Solids in nanosize scale are known to exhibit exceptional mechanical properties, including strengths in the range of tens of gigapascals and elastic strains up to and beyond 10%. These extraordinary properties originate from the strength of the interatomic bonds within the solids. The same bonds also exist in bulk engineering materials, yet till today we have not been able to access this intrinsic ability of materials, despite our over a century of effort in modern materials science trying to strengthen them. In this presentation I explore with you a new concept of using the martensite as the key to unlock the intrinsic abilities of solids for creating bulk materials of neat ideal strengths, and other possible properties.

In this presentation I will also showcase some early works we have attempted, by creating NiTi-X nanostructured metallic bulk composites. In these composites we are able to achieve ultra-large elastic lattice strains up to 6% (implying strengths of several gigapascals) in the nanoinclusions embedded in or thin films deposited on NiTi. The strategy is based on a new concept of “collective atomic load transfer” using martensitic transformation as an atomic distributor and lattice strain equalizer. The achievement of such ultra-large elastic strains also has other implications, in particular in “elastic strain engineering”, in which we can engineer the many physical and chemical functional properties of solid materials by the application of ultra-large elastic strains.