Investigation of Thermoelastical Martensitic Transformations and Structure in New Composition of CuAlMnTi Shape Memory Alloy.

Abstract

Shape memory alloys (SMAs) are a class of smart materials. These intelligent alloys have unique thermomechanical properties such as shape memory effect (SME) and superelasticity (SE) which enable them to utilize in numerous modern technological and industrial applications. Their macroscopic shape changing ability (SME) is based on their thermoelastical, isothermal and atomically non-diffusional martensitic phase transformations between low temperature phase (martensite) and high temperature phase (austenite). When these unusual alloys are mechanically deformed at low temperature (in martensite phase), they can return back to their first pre-deformed shape by heating and increasing their temperature up. In such processes the martensite phase changes into parent austenite phase. Conversely, when they are cooled down from high temperatures, the austenite phase converts into martensite phase, but at this time shape change does not occur and this one way shape changing ability is called one way shape memory effect (OWSME). SMAs are also acquired two way shape memory effect (TWSME) property by some trainings, and after once they are gained TWSME feature in them, then they can go and return between two different unauthentic shapes by heating and cooling them. In this work, the thermoelastical martensitic  transformation phenomena of CuAlMnTi shape memory alloy with a new chemical composition was investigated by thermal and structural measurements and analyses including DSC, EDX, XRD and optical microscopy. The characteristic transformation phase start and finish temperatures, hysteresis, enthalpy and entropy change parameters were identified by DSC data analyses and calculations. The existing martensite phase forms on the alloy surface and in the alloy  texture at room temperature were detected by XRD and optical measurements, respectively.