Breakdown of Shape Memory Effect in Bent Cu-Al-Ni Nanopillars: When Twin Boundaries Become Stacking Faults.
2016
Liu, Lifeng | Ding, Xiangdong | Sun, Jun | Li, Suzhi | Salje, Ekhard KH
Bent Cu-Al-Ni nanopillars (diameters 90-750 nm) show a shape memory effect, SME, for diameters D > 300 nm. The SME and the associated twinning are located in a small deformed section of the nanopillar. Thick nanopillars (D > 300 nm) transform to austenite under heating, including the deformed region. Thin nanopillars (D < 130 nm) do not twin but generate highly disordered sequences of stacking faults in the deformed region. No SME occurs and heating converts only the undeformed regions into austenite. The defect-rich, deformed region remains in the martensite phase even after prolonged heating in the stability field of austenite. A complex mixture of twins and stacking faults was found for diameters 130 nm < D < 300 nm. The size effect of the SME in Cu-Al-Ni nanopillars consists of an approximately linear reduction of the SME between 300 and 130 nm when the SME completely vanishes for smaller diameters.
Show more [+] Less [-]This work was supported by the National Natural Science Foundation of China (Grant Nos. 51171140, 51231008, 51321003and 51320105014), the 973 Program of China (2012CB619402), the 111 Project of China (B06025), and EPSRC (EP/K009702/1). The authors thank Xiaolei Wu for helpful discussion on this paper.
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