Pseudoelastic Response of Ion Implanted Nickel-Titanium Shape Memory Alloy: Combining Experimentation and Forward Modeling

This work reports on a novel experimental-simulation approach to determine the effect of Ni-ion irradiation on the pseudoelastic-plastic response of Ni50.5at%Ti49.5at% and Ni50.8at%Ti49.2at% shape memory alloys. Though experimental-simulation efforts in literature have predicted the load-displacement nanoindentation response of Nickel Titanium [1], there is, to our knowledge, no existing effort to produce pseudoelastic stress-strain curves for nickel-titanium based on experimental indentation data. In a first-of-its-kind approach, our goal is to forward model both the pseudoelastic transformation and plastic response of nickel-titanium alloys by coupling nanoindentation measurements with a Microstructural Finite Element (MFE) model developed by this research group [2]. The nanoindentation approach is attractive since the volume of irradiated matter produced in the experiments does not lend itself to differential scanning calorimetry or traditional mechanical testing. The fluences used in the ion irradiation investigation are predicted to generate a range of irradiation damage distributions spanning from point defects to full amorphization, based on Stopping Range of Ions in Matter simulations and prior literature [3]. A high throughput approach is employed to map the variation in room temperature nanoindentation response within the depth-dependent damage profile. Different sequences of thermal cycling, irradiation, and mechanical deformation are used to study the path-dependent effects of processing. The forward modeling approach is used to furnish material parameters as a function of irradiation and processing history. These include critical temperatures for transformation, enthalpy of phase transformation, and critical resolved shear stress for slip activation in austenite.

This work is supported by the Department of Energy, Basic Energy Sciences (DE-SC0001258) and the Center for Integrated Nanotechnologies (2019BC0126).

CINT Acknowledgements: https://cint.lanl.gov/publications/index.php

[1] https://doi.org/10.1016/j.actamat.2006.08.013

[2] https://doi.org/10.1016/j.ijplas.2015.12.007

[3] https://doi.org/10.1080/00337578508222535