Martensitic transformation was investigated for Ti-rich Ti-Ni gas-atomized powders as a function of powder size. The large powders clearly exhibit multiple martensitic transformations on both cooling from austenite to martensite and vice versa. With increasing powder size, the minor martensitic transformation temperatures increase and the amount of heat accompanying the minor transformation also increases. However, the main martensitic transformation temperature is almost the same, irrespective of the powder size. Microstructures of the as-atomized powders were examined to clarify why the powders exhibit the multiple martensitic transformations.
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