Elastic properties of Cu–Al–Ni shape memory alloys studied by dynamic mechanicalanalysis

Abstract

The elastic properties of Cu–Al–Ni single crystals have been studied during forward andreverse martensitic transformation by dynamic mechanical analysis. Measurements wereperformed for two alloys, occurring in austenitic (Cu–14%Al–4%Ni) and martensitic(Cu–13.7%Al–3%Ni) phases at room temperature. Investigation of elastic and dampingproperties was performed for several frequencies of the oscillating force. Evolution ofdamping in cooling/heating measurements gave information about internal friction duringforward and reverse martensitic phase transformations. Characteristic temperatures ofmartensitic transformation were determined by dynamic mechanical analysis and comparedwith optical micrographs of samples’ surfaces and with previous results fromdifferential scanning calorimetry. In addition, comparison of elastic properties in pureaustenitic and martensitic phase during ageing was made. The paper presents astep-by-step analysis of experimental results showing the causes which lead toobserved changes of elastic properties at martensitic transformation or with time.