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Here we report on compressive stress-strain behavior, ordinary and burst-like shape
memory (SM) strain recovery, and associated caloric effects in Cu - 14.02% wt. Al - 4.0%
wt. Ni single crystals which have multiphase martensitic structure at room temperature. The
effect of repetitive thermo-mechanical cycling on the recovery of the shape memory
deformation is investigated. The stress-strain curves of the specimens are smooth in all tests.
Immediately after quenching, crystals exhibited burst-like strain recovery accompanied by the
jumping of the whole specimen in each deformation-recovery. After several days from
quenching, crystals showed weaker jumping which was also reducing with each thermomechanical cycle. The average values of the integral thermal effect remained the same from
cycle to cycle. Although the starting temperature of burst-like reverse martensitic
transformation stochastically varied from cycle to cycle, it showed a general tendency to
decrease with an increasing number of cycles until the burst-like effect disappears completely.
The heating rate does not significantly affect the position of the DSC peak. Low temperature
aging of the specimens resulted in the gradual weakening and disappearance of the burst-like
strain recovery. Thus, thermal treatment and loading regimes should be optimized for highcycle applications of Cu-Al-Ni alloys.
Keywords: : shape memory alloys (SMA); strain recovery; martensitic phase transformation; differential scanning calorimetry (DSC) |
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