title: Exceptional Resilience of Small-Scale Au30Cu25Zn45under Cyclic Stress-Induced Phase Transformation.
abstract: Shape memory alloys that produce and recover from large deformation driven by martensitic transformation are widely exploited in biomedical devices and microactuators. Generally their actuation work degrades significantly within first a few cycles and is reduced at smaller dimensions. Further, alloys exhibiting unprecedented reversibility have relatively small superelastic strain, 0.7%. These raise the questions of whether high reversibility is necessarily accompanied by small work and strain and whether high work and strain is necessarily diminished at small scale. Here we conclusively demonstrate that these are not true by showing that Au30Cu25Zn45pillars exhibit 12 MJ m-3work and 3.5% superelastic strain even after 100 000 phase transformation cycles. Our findings confirm that the lattice compatibility dominates the mechanical behavior of phase-changing materials at nano to micron scales and points a way for smart microactuators design having the mutual benefits of high actuation work and long lifetime.
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Xiaoyue
authors.initials: X
authors.lastname: Ni
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Julia R
authors.initials: JR
authors.lastname: Greer
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Kaushik
authors.initials: K
authors.lastname: Bhattacharya
authors.affiliation: Department of Aerospace Engineering and Mechanics, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Richard D
authors.initials: RD
authors.lastname: James
authors.affiliation: Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Xian
authors.initials: X
authors.lastname: Chen
keywords: Nanomechanics; in situ nanocompression; nano- and microactuation