The effect of aging treatment on the microstructure and thermodynamic parameters of CuA1Ni-Mn shape memory alloys (SMAs)

Abstract

This thesis presents the effect of heat treatment on the microstructure and thermodynamic parameters of CuAlNi -Mn SMA. The effects of different aging temperatures of 300oC, 400oC and 500oC at various aging times were evaluated using the optical microscopy, FESEM and the XRD, to investigate their microstructure and phase transformation. The martensite and austenite transformation temperatures of CuAlNi -Mn SMA have been determined by the differential scanning calorimetry (DSC), while the hardness property using Vickers hardness. The variation of the structure and properties of alloy were influenced by the morphology and the type of the phases obtained. The observation revealed that the grain size and the grain boundary of CuAlNi -Mn SMA increase with increasing the aging temperatures and aging times. Due to this, the values of Vickers hardness were observed to decrease at elevated temperatures and prolonged aging times. On the other hand, the changes of thermodynamic parameters were observed with regard to the variation of aging temperatures and aging time. The enthalpy and entropy were observed increase with increasing the aging temperatures and aging times.