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

The elastic properties of Cu–Al–Ni single crystals have been studied during forward and reverse martensitic transformation by dynamic mechanical analysis. Measurements were performed 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 damping properties was performed for several frequencies of the oscillating force. Evolution of damping in cooling/heating measurements gave information about internal friction during forward and reverse martensitic phase transformations. Characteristic temperatures of martensitic transformation were determined by dynamic mechanical analysis and compared with optical micrographs of samples' surfaces and with previous results from differential scanning calorimetry. In addition, comparison of elastic properties in pure austenitic and martensitic phase during ageing was made. The paper presents a step-by-step analysis of experimental results showing the causes which lead to observed changes of elastic properties at martensitic transformation or with time.