Shape memory properties and microstructural evolution of rapidly solidified CuAlBe alloys

In this work, the effects of Be addition on the microstructure and phase transformation temperatures of Cu-12Al-xBe (x = 0.4, 0.5 and 0.6 wt.%) shape memory alloys fabricated by using the arc-melting and melt-spinning techniques have been investigated. X-ray diffraction analysis revealed that the arc-melted alloys consisted of austenitic beta(1), martensitic beta(1)' and gamma(2) precipitate phases, whereas melt-spun ribbons were composed of a fully martensitic phase. The average grain size of martensitic phases in melt-spun ribbons was determined by electron microscopy images, showing a decrease with increasing Beryllium (Be) amount. Moreover, it was found that the Be addition in the arc-melted alloys had a distinct effect on the morphology of the gamma(2) precipitate phase. Transmission electron microscopy analysis showed that the thickness of martensitic plates in the melt-spun ribbons reduced with increasing Be addition. In a differential scanning calorimeter analysis, no martensitic transformation (M-s) peak was observed in arc-melted alloys, but it was clearly detected in melt-spun ribbons, in which M-s decreased dramatically with increasing Be addition. The improvement in the shape memory ability of melt-spun ribbons was explained in terms of the refinement in grain size and martensitic plates. (C) 2013 Elsevier Inc. All rights reserved.