Developing high-performance NiTi shape memory alloy for sustainable elastocaloric cooling

Objective

Cooling is vital for human well-being, yet current cooling systems predominantly rely on vapor-compression technology, which consumes nearly 20% of global electricity and accounts for approximately 7.8% of worldwide carbon emissions. Elastocaloric cooling, based on the stress-induced latent heat associated with reversible martensitic transformations in NiTi shape memory alloys (SMAs), offers a promising energy-efficient and eco-friendly alternative. However, conventional NiTi SMAs often fail to simultaneously achieve high cooling capacity and low energy dissipation due to suboptimal microstructures, which significantly reduces their overall cooling efficiency. This project aims to overcome this trade-off by engineering gradient microstructures in NiTi SMAs, consisting of coarse grains at the surface and fine grains in the core. A novel processing route, integrating cold rolling with advanced laser surface annealing, will be developed to realize this hierarchical architecture. In parallel, a dedicated testing platform will be established to evaluate elastocaloric performance under application-relevant conditions. With fellowship support, the project will establish quantitative microstructure–property relationships and construct a database to enable machine-learning-assisted optimization of processing parameters and microstructural design. Particular emphasis will be placed on understanding how structural gradients influence the martensitic transformation and cooling performance of heterogeneous NiTi SMAs. The resulting insights will advance the fundamental science of SMAs, drive the development of next-generation sustainable cooling technologies, and reinforce United Kingdom's leadership in climate solutions. This research proposal will be hosted by Prof. Minh-Son Pham from the Imperial College London.