Novel Experiments and Simulations to Study Transformation, Plasticity, and Precipitate Effects in Shape Memory Alloys

Combining novel experimental approaches with simulations of the underlying phenomena can be used to study a range of physical processes in shape memory alloys. Here, we study the connection between transformation and plasticity in near equiatomic NiTi shape memory alloys, the role of precipitates in promoting and/or suppressing transformation in NiTiHf high temperature shape memory alloys, and the effects of texture and grain neighborhood on shape memory performance at the grain-to-grain scale. Each of these examples highlights the close coupling between experiments and simulations needed to both calibrate the simulations and guide interpretation of the experimental results. Particular experimental techniques include: high resolution and conventional transmission electron microscopy, micron-scale pillar compression testing, differential scanning calorimetry, and load-bias thermal cycling. Particular simulation techniques include Fourier transform, finite element, and phase field methods that incorporate anisotropic elasticity, thermal expansion, crystal-based transformation, and crystal-based plasticity. Together, they provide insight to the processes that drive shape memory performance across microstructural scales. This work is supported by the DOE, Office of Basic Sciences, DE-SC0001258 (John Vetrano, Program manager) and the NSF, Division of Materials Research, DMR-1207494.