Effect of Titanium on the Martensitic Transformation Temperature of Cu-14Al-4Ni Shape Memory Alloy Rapidly Solidified

The present research aimed to analyze the influence that different contents of titanium (x = 0.5, 0.6 and 0.7 wt.%) have on the martensitic transformation temperature of a Cu-14Al-4Ni (wt.%) SMA (shape memory alloy). The Cu-14Al-4Ni-xTi samples were casted in an arc-melting furnace and rapidly solidified. All samples underwent heat treatment in a tubular furnace at a temperature of 1,100 °C for 30 min and water quenched at 25 °C. Subsequently, samples were analyzed by SEM (scanning electron microscopy) with EDS (energy dispersive spectroscopy), XRD (X-ray diffraction) and DSC (differential scanning calorimeter). SEM images and XRD patterns showed that the presence of titanium modified the alloy’s microstructure, induced the formation of three titanium rich phases called “X” phase (CuNi2Ti, Cu3Ti and AlCu2Ti) and reduced the presence of the brittle phase γ2 (Cu9Al4) for samples with 0.6 and 0.7 wt.% Ti. The titanium added to the copper based SMA also functioned as a refiner, reducing GS (grain size) up to approximately 80% with the increase of Ti content. DSC results exhibited low enthalpy levels, hysteresis, as well as low start martensitic transformation temperatures.