Mechanics and multi-physics of phase transformations in shape memory alloys under extreme dynamic environments

Efficient power generation/absorption will remain a crucial aspect of disruptive technology in a society with rising energy demands for sustenance (e.g., power generation) to scientific curiosity (e.g., space exploration). Multi-functional shape memory alloys (SMAs) form the core of many such technological breakthroughs. The multi-functionality of SMAs originates from solid-solid phase transformations, i.e., changes in the atomic lattice structure, driven by local mechanical, thermal or magnetic fields. Project MultiPhaseXtrM identifies a radically different and unexplored regime for the operation of SMAs — large, multiaxial dynamic impact and shock stresses (up to 10 GPa) within short time scales (down to nanoseconds), referred to as “extreme dynamic environments”. Exploiting multi-physical coupling in SMAs under these extreme conditions could scale up their power conversion capabilities by orders of magnitude. Two broad scientific questions form the core of Project MultiPhaseXtrM: (1) How do thermodynamic states evolve in SMAs under extreme dynamic environments and coupled thermal/magnetic fields? (2) How do these states drive the evolution of phase transformations at short time scales? Dynamic impact experiments and high-speed instrumentation, developed in house, will probe this multi-scale behavior in single-crystal SMAs under carefully-controlled strain rates and multi-axial stress states, while advancing experimental science towards resolving short length and time scales, simultaneously. Multi-scale data sets will be analysed within continuum theoretical frameworks to discover the kinetic laws for phase transformations across the range of multi-physical conditions explored. The impact of this program will extend beyond, from designing multi-ferroic SMAs with programmable multi-functionality under these extremes, to understanding the role of stress-induced phase transformations in dynamic material strength, material synthesis and extreme geological events.