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 Au30Cu25Zn45 pillars exhibit 12 MJ m-3 work 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.
Bibliographical noteFunding Information:
X.C. acknowledge the financial support of the HK Research Grants Council through Early Career Scheme under Grant 26200316 and UGC Fund B002-0172-R9358. X.N. and J.R.G. acknowledge the financial support of the U.S. Department of Energy through Early Career Research Program under Grant DE-SC0006599. K.B. and R.D.J. acknowledge the financial support of the Air Force Office of Scientific Research through MURI Grant FA9550-12-1-0458. The research of R.D.J. was also supported by NSF-PIRE (OISE-0967140), MURI (W911NF-07-1-0410 administered by AFOSR), ONR (N00014-14-1-0714), NSF-DMREF 1629160, the RDF Fund of the Institute on the Environment (UMN), and AFOSR (FA9550-15-1-0207).The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
- in situ nanocompression
- nano- and microactuation