| In order to refine the grain size and to improve their mechanical properties in Cu base shape memory alloys, the methods such as the addition of alloying element, powder metallurgy and rapid solidification technology are being studied. This work was carried out to establish the basic concept for attaining the above purpose by studying on the changes in the grain size and studying on the forming behavior of γ₂ precipitates by aging of the melt spun ribbons manufactured by single roll melt spinning. Melt spun ribbons, as it is, exhibited shape memory behavior. Grain size in the melt spun ribbons was on the whole below about 3㎛, it was finer than that of castings. When they were aged, the phenomena of the increase in hardness and of the disappearance in the shape memory ability were started generally after about 10³ seconds at 400℃, 10^5 seconds at 300℃ and l0^6 seconds at 200℃ in ribbons. But in case of the alloy being added compoundly Ti, Zr and B, the phenomenon of the increase in hardness appeared after about 10⁴ seconds and the shape memory ability was maintained for the longest time at 400℃. The cause of the phenomena of the increase in hardness and of the disappearance in the shape memory ability is due to the formation of the γ₂ precipitates. In this work it is considered that the alloy being aged compoundly Ti, Zr and B is more superior than any other alloys from the viewpoint of the grain size, aging characteristics and shape memory ability. |
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