- Fırat Üniversitesi Fen Bilimleri Dergisi
- Cilt: 36 Sayı: 1
- Thermokinetic and Structural Shape Memory Effect Characteristics of Novel Quaternary CuAlNiCr HTSMA
Thermokinetic and Structural Shape Memory Effect Characteristics of Novel Quaternary CuAlNiCr HTSMA
Authors : Oktay Karaduman, Iskender Özkul, Gökhan Istek, Canan Aksu Canbay
Pages : 25-34
View : 58 | Download : 74
Publication Date : 2024-03-28
Article Type : Research
Abstract :CuAlNi shape memory alloys (SMAs) are one of the most prominent Cu-based SMAs mainly due to their shape memory properties at high temperatures. Therefore, they are interested in high temperature SMA applications. Their good thermal stability but brittleness originated from their coarse grain size are their other pros and cons. In this study, the low-cost quaternary CuAlNiCr high-temperature SMA (HTSMA) with a new unprecedented chemical composition including trace amount of chromium element was fabricated by arc melting technique. After arc melting process, traditional homogenization of small alloy samples in the high β-phase temperature region and quenching them in iced-brine water were proceeded. To characterize the shape memory effect property of the alloy, differential calorimetry and microstructural X-ray diffraction (XRD) tests were carried out. The cyclic DSC (differential scanning calorimetry) tests carried out at various heating/cooling rates showed the splendid endothermic and exothermic peaks of reversible martensitic phase transformations in the temperature range between around 150-220 °C, thence the produced alloy is qualified as a high-temperature SMA. Using DSC peak analysis data, the finish and start temperatures of every martensitic phase transition, hysteresis gap, plus some other important thermodynamic parameters\' values were also determined. Among them, the high enthalpy change amounts occurred during the transformations implied the good shape memory effect feature of the alloy. A DTA (differential thermal calorimetry) test taken at only one heating/cooling rate revealed both the reversible martensitic transformation peaks and the other phase transition peaks at higher temperatures. The consecutive phase transition step peaks of β\'1→ B1(L21)→B2→A2 on the heating-part of the DTA thermogram curve of the alloy were observed as similar to those seen in the other Cu-based shape memory alloys. Furthermore, at room temperature, the presence and types of the martensite phases formed in the alloy were revealed by the XRD pattern of the alloy obtained by using CuKα radiation. The results showed that the novel CuAlNiCr high-temperature SMA can be useful in the high-temperature SMA applications.Keywords : Yüksek sıcaklık şekil hafızalı alaşım, CuAlNiCr, martensitik dönüşüm, DSC, DTA