The effect of ageing and quenching media on thermodynamic parameters and structure in Cu-based SMAs

In this study, four samples of different ternary and quaternary composition SMA as SI-1,SI-2, SI-3 and SI-4 of Cu-22.22Al-3Fe(at%), Cu-22.79Al-2.59Fe-2.44Mn(at%), Cu-22.79Al-5.42Fe-0.98Mn(at%) and Cu-21.52Al-3.49Fe-1.95Mn(at%) was produced respectively by arc melting. The SI-2 and SI-4 samples responded. Quenching the samples were made in four different media (Iced water, boiling water, liquid nitrogen, and room temperature). The characteristic martensitic transformation temperatures and thermodynamic parameters of all the samples investigated by differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are taken at different heating/cooling rates. The characteristic direct martensitic phase transitions of most of the samples occurred at high temperature in heating/cooling DSC curves. Austenite starts the temperature of the samples are above 100°C and that's why these SMAs samples are called high-temperature shape memory alloys (HTSMAs). The X-ray analyses were made at room temperature to determine the structural features, the diffraction planes and their corresponding phases of all the samples. The martensite planes were observed for all the samples resulted from β1′(18R) planes and the average crystallite size was determined for the alloy samples using Debey-Scherrer equation. The results of the new quaternary HTSMAs of different composition (SI-1, SI-2, SI-3, and SI-4) were investigated along with SI-2 and SI-4 treated samples. Quenched samples in different media results were amazing, as the effect of these different media on the thermodynamic and structural properties of the samples were not as it was expected and it is very obvious that the effect of boiling water and liquid nitrogen quenching medium were very close to each other and mostly better than the result of usual iced water quenching medium on the treated samples.