| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 90 === In this experiment, eight kinds of Cu-Al-Be alloys with different chemical compositions were melted at 1100℃ in evacuated quartz capsules. After homogenized and hot rolled, the specimen were quenched into ice-water from 850℃ and aged at 200℃ or 400℃. Then they were investigated by electrical resistance measurement, hardness test, tension test and shape memory recovery test to get their characteristics. Futher studies were also conducted by SEM, TEM and XRD in order to identify the different phase structure of the alloys. Besides, thermal cycling experiments were used to study the effect of thermal cycling on the shape memory alloys.
The results show that, the martensite and parent phase of these alloys are M18R and DO3 respectively. The precipitates of hypoeutectoid alloys(Al＜11.8 wt％) aged at 200℃ and 400℃ are α1-plate(M18R) and α(FCC) respectively. On the other hand, the precipitates of hypereutectoid alloys(Al＞11.8 wt％) aged at 200 and 400℃ are all γ2(Al4Cu9, D83). These precipitates affect the transformation temperatures(Ms, Mf, As, Af), increase the hysteresis temperatures(Af-Ms) and deteriorate the shape memory recoveries of these specimens.
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