The Study of Large Shape Memory Type Products-the plastic deformation in Cu-12%A1 alloy-

1994 Fiscal Year Final Research Report Summary

• Project/Area Number: 05650105
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: Materials/Mechanics of materials
• Research Institution: KOCHI NATION COLLEGE OF TECHNOLOGY
• Principal Investigator: FUJIWARA Shoji KOCHI NATIONAL KOLLEGE OF TECHNOLOGY,DEPT.OF MECHANICAL ENGINEERING,PROFESSOR, 機械工学科, 教授 (90026328)
• Co-Investigator(Kenkyū-buntansha): MIWA Shintaro KOCHI NATIONAL KOLLEGE OF TECHNOLOGY,DEPT.OF MECHANICAL ENGINEERING,PROFESSOR, 機械工学科, 教授 (60044202)
• Project Period (FY): 1993 – 1994
• Keywords: Shape Memory / Copper Alloy / Deformation / Hot-Rolling / Martensite

Research Abstract

A Cu-12%A1 alloy was prepared by vacuum induction melting. The obtained alloy was found to be very brittle at room temperature and not to be cold-rolled without propagation of cracks. It was considered that the very large grain size (larger than 500mum) of this alloy caused the grain boundary embrittlement. So, small amount of other elements was added in this alloy to get fine grains. For exsample, the grain size in a Cu-12%A1-0.01%B alloy was observed to be very small (smaller than 50mum). And by the internal friction measurement, this alloy was found to show same results as the Cu-12%A1 alloy. And there was little difference in the martensite morphology between them. It was considered that there was no effective influence on shape memory effect. But its mechanical property at room temperature was not so good. To study of the fracture mechanism in the 0.01%B alloy, the scanning electron microscopy was used. In spite of the fine grain alloy, grain boundary fracture was observed. The re ason was considered that there were the ordered matrix and the brittle grain boundaries in the alloy.
In the Cu-12%A1 alloy, the behavior of phase transformation was investigated by the electric resistivity measurement during continuous heating with the rate of 10ﾟC/min. And clearly phase transformation was observed. Though this alloy was so brittle at room temperature, at high temperature it showed good ductility without hardly work-hardening. And the heavily hot-rolled specimen was found to have good mechanical properties. And more than 10 cycles of shape memory effect in the heavily hot-rolled specimen was recognized.
To study of large products of a Cu-12%A1 alloy, some rings with a slit were prepared by cutting the bulk material. After heating at high temperature, they were deformed at low temperature and then again heated. So, clearly shape mempry effect was observed in this experiment. Namely, by using a Cu-12%A1 alloy it was considered that the large shape memory type products became useful in future by means of settling the problems of the high phase transformation temperature and the lack of perfect reversibility in SME.