COOLING CONDITION EFFECTS ON TRANSFORMATION TEMPERATURE AND MICROSTRUCTURE OF Cu81Al13Ni4Ti2 SMA.

The present communication reports the production of Cu81-Al13-Ni4-Ti2 shape memory alloy (SMA) by an arcmelting method. A piece of this alloy is subjected to heat treatment at 930°C for 30 min and then shock-cooled in liquid nitrogen (-196°C), alcohol (0°C) and saline ice water (+6°C). Differential Scanning Calorimetry (DSC) is performed on samples with no heat treatment and on those subjected to three different heat treatments. It is found that the chosen heat treatments increase significantly the phase transformation temperatures of the shape memory alloy. Some changes in the microstructure of the alloy are also observed after the heat treatment. The grain boundaries become more pronounced, while the martensite plates increase in the samples which are shock-cooled in alcohol and saline ice water. The crystalline structures of the samples are investigated at room temperature. The XRD diffractograms reveal that bı phase (martensite phases) increases in the alloys subjected to heat treatment. [ABSTRACT FROM AUTHOR]