Influence of process factors on shape memory effect of CuZnAl alloys
(School of Materials Science and Engineering, Jiangsu University,
Zhenjiang 212013, China)
Zhenjiang 212013, China)
Abstract: Thermal cycle training of CuZnAl shape memory alloys with different transformation temperatures was carried out. The influence of different pre-strains, heat treatments and media on the shape memory effect(SME) of CuZnAl alloys with different transformation temperatures was studied by means of scanning electron microscopy(SEM) and X-ray diffractometry(XRD). Experimental results show that despite respective variation in heat treatment, medium and cycling number, the recovery rate always decreases as pre-strain increases. The decline is obvious when pre-strain is less than 2.6% but not so sharp when pre-strain exceeds 2.6%. Larger pre-strain results in more than one slip system and causes intercutting of the martensite strips among martensitic variants, then leads to the decline of SME. The SME of alloys with transformation temperatures below 347 K is larger than that of alloys beyond 361 K by 20%−40%. The recovery rate of two-step aged alloy is higher than that of step-quenched alloy by 20%−25%. During thermal cycling, the recovery rate in oil is better than that in water.
Key words: CuZnAl shape memory alloys; pre-strain; transformation temperature; shape memory effect; thermal cycling; heat treatment