Materials Transactions Online

Materials Transactions, Vol.44 No.12 (2003) pp.2732-2735
© 2003 The Japan Institute of Metals

Shape Memory Effect Associated with FCC--HCP Martensitic Transformation in Co-Al Alloys

Toshihiro Omori1, Yuji Sutou1, Katsunari Oikawa2, Ryosuke Kainuma1 and Kiyohito Ishida1

1Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
2National Institute of Advanced Industrial Science and Technology, Tohoku Center, Sendai 983-8551, Japan

The martensitic transformation and shape memory (SM) effect in Co-Al alloys containing 0--16 at%Al were investigated by differential scanning calorimetry (DSC) and bending tests. It was found that the martensitic transformation temperatures decrease and the thermal hystereses increase with increasing Al content. It was also found that an incomplete SM effect occurring in pure Co can be enhanced by the addition of Al over 4 at% and that Co-Al alloys containing Al over 10 at% show an excellent SM effect. Co-Al SM alloys possessing high reverse transformation temperatures over 200°C and martensitic transformation in the ferromagnetic state show promise as a new type of SM alloys.

(Received 2003/9/17; Accepted 2003/10/15)

Keywords: shape memory effect, ε martensite, martensitic transformation temperature, cobalt-aluminum, high-temperature shape memory alloy

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