The effect of ageing on the damping properties of Cu–Al–Ni shape memory alloys

Abstract

Dynamic mechanical analysis (DMA) ofβ-phase aged single-crystal Cu–Al–Ni alloys was conducted to investigate the changes in theinternal friction (IF) through the thermoelastic martensitic transformation temperature regime.Two alloys of different compositions, one in the martensitic and the other in the austenitic stateat room temperature, were examined. Ageing of the alloys at three different temperatures,Ta (473, 523 and 573 K), shows an increase in the transformation temperatures due to thesuccessive martensitic transition () and γ2 precipitate formation. Correspondingly, a progressive reduction in the IF peak in thetransition regime with increase in the ageing temperature was observed in both the alloys.Formation of precipitates, which hinder the mobility of the martensite variant andparent/martensite interfaces, and an increase in their volume fraction with ageing arecauses for the observed IF reduction.