Size effect on the deformation mechanisms of nanocrystalline platinum thin films

Abstract

This paper reports a study of time-resolved deformation process at the atomic scale of a nanocrystalline Pt thin film captured in situ under a transmission electron microscope. The main mechanism of plastic deformation was found to evolve from full dislocation activity-enabled plasticity in large grains (with grain size d > 10 nm), to partial dislocation plasticity in smaller grains (with grain size 10 nm < d < 6 nm), and grain boundary-mediated plasticity in the matrix with grain sizes d < 6 nm. The critical grain size for the transition from full dislocation activity to partial dislocation activity was estimated based on consideration of stacking fault energy. For grain boundary-mediated plasticity, the possible contributions to strain rate of grain creep, grain sliding and grain rotation to plastic deformation were estimated using established models. The contribution of grain creep is found to be negligible, the contribution of grain rotation is effective but limited in magnitude, and grain sliding is suggested to be the dominant deformation mechanism in nanocrystalline Pt thin films. This study provided the direct evidence of these deformation processes at the atomic scale.

Tailoring magnetic and mechanical properties of mesoporous single-phase Ni–Pt films by electrodeposition

“…5 The inversion of the Hall-Petch relationship due to a change in the mechanism of plastic deformation was determined for nanocrsytalline Pt for grain sizes lower than 10 nm. 44 The Ni-Pt films possess hardness values lying between 4 GPa and 6 GPa. The generally high values are a result of the nanocrystallinity, however, internal stresses may also contribute to an increased hardness.…”

Comparative Study on Microstructural Stability of Pre-annealed Electrodeposited Nanocrystalline Nickel During Pack Rolling

“…Instead, the proportion of large grains (above 50 nm) increases. Based on previous studies on dislocation activities in deformed grains, full dislocations would gradually start to dominate the deformation of large grains [ 30 – 33 ]. Thus, it is not difficult to understand the SFP of the interface M/M is much higher than that of the interface M/R.…”

Micrometer-sized electrically programmable shape-memory actuators for low-power microrobotics

“…Despite being ultrathin, these actuators generate a substantial force. On the basis of beam theory (19), a square SEA with a change in curvature of 0.5 m −1 , which is close to the platinum yield strain (32)(33)(34)(35), generates a force of 30 nN at its end (see text SII), allowing the micropositioning stages to carry payloads of 20 to 50 nN. This force is over an order of magnitude higher than those produced by optical traps and about 10,000 times the weight of these devices.…”