Functional alloys and phase transformations
Shape memory alloys are mysterious alloy that returns to their original shape after being deformed and warmed up. This "shape memory effect" is closely related to a phase transformation called thermoelastic martensitic transformation. Our laboratory aims to elucidate the phase transformation mechanism through direct observation by electron microscopy.
In-situ observation, in which the materials are heated, cooled, or stressed in the electron microscope, is effective for directly observing phase transformations. In our laboratory, we are trying to elucidate the phase transformation process using state-of-the-art in-situ observation equipment. The lower right photo shows the martensitic transformation in a Ti-Ni shape memory alloy, successfully observed directly. The martensitic phase is observed to expand as the temperature is lowered.
>> Electron Microscopes
Due to their high biocompatibility, titanium alloys are widely used not only for structural materials such as jet turbines but also for medical devices such as dental implants and artificial bones. On the other hand, β-type titanium alloys are known to undergo a characteristic phase transformation called omega phase transformation, which has a significant effect on mechanical properties, so the phase transformation mechanism needs to be clarified.