A team led by Academician Sun Jun from the National Key Laboratory for Strength of Materials at Xi'an Jiaotong University (XJTU) has developed a TiNiCu superelastic alloy that exhibits both large functional response and excellent cyclic stability by combining precise composition design with nanostructure control.

The study revealed that precisely regulating the Ni/Ti ratio allows the alloy to undergo a B2-B19 phase transformation with excellent lattice compatibility at a relatively low Cu content. This reduces phase transformation hysteresis and maintains good workability.

The designed TiNiCu alloy ingot exhibited almost unchanged phase transformation temperature and latent heat after 5,000 thermal cycles. Multi-scale in-situ characterization further revealed that the alloy possesses a unique microdomain memory effect during phase transformation cycling.

Following further cold working and low-temperature annealing, the alloy ingot yielded nanocrystalline sheets and kilogram-level nanocrystalline wires, which demonstrated an adiabatic temperature change exceeding 20 K at room temperature.

The wire maintained approximately 6 percent superelastic strain over 6,000 tensile cycles. Alloy micropillars could withstand over 1 million compression cycles while retaining a recoverable strain of 4.3 percent.

The developed TiNiCu alloy has achieved a leading level in both functional response and cyclic stability within current TiNi-based alloy systems, offering new alloy design ideas and realization pathways for overcoming the aforementioned bottlenecks.

These research findings, titled Design of a Superelastic Alloy Uniting Large Functional Response and Exceptional Cyclic Stability, were published in the internationally renowned academic journal Advanced Functional Materials.