Controlling of Transformation Temperatures of Cu-Al-Mn Shape Memory Alloys by Chemical Composition

The Cu-Al-Mn shape memory alloys having various chemical compositions were prepared by arc melting method to control the phase transformation parameters. The phase transformation parameters and structural properties of the alloys were investigated by differential scanning calorimetry and optic microscopy, respectively. The effects of the chemical composition on characteristic transformation temperatures, enthalpy and entropy values of Cu-Al-Mn ternary system were investigated. The characteristic transformation temperatures of austenite and martensite phase ($A_{s}$, $A_{f}$, $M_{s}$, and $M_{f}$) are increased with change in the chemical composition of the alloys. The average crystallite size for the alloys was calculated to determine the effect of aluminum and manganese compositions on the transformation temperatures. The change in transformation temperatures indicates the same trend with change in crystallite size. The obtained results suggest that the phase transformation parameters of the Cu-Al-Mn alloys can be controlled by Al and Mn contents

The effect of the aging period on the martensitic transformation and kinetic characteristic of at % Cu(68.09)Al(26.1)Ni(1.54)Den(4.27) shape memory alloy

WOS: 000400779400006In this work, the effect of aging period on the characteristic transformation temperatures, thermodynamic parameters and structural variations of CuAlNiMn shape memory alloys were investigated. Aging was performed at above the austenite finish temperature of the un-aged specimen (120A degrees C) for six different retention times, namely 1h, 2h, 3h, 4h, 5h and 6h. The changes in the transformation temperatures were examined by differential scanning calorimetry at different heating/cooling rates. The aging period was found to have an effect on the characteristic austenite and martensite transformation temperatures and thermodynamic parameters such as the enthalpy and entropy of alloys. High-temperature order-disorder phase transitions were determined using a differential thermal analysis, which showed that all the un-aged and aged specimens had an A2 -> B2, B2 -> L2(1) and an L2(1) -> 9R, 18R transition. The structural analysis of the un-aged and aged specimens was performed through X-ray diffraction measurements at room temperature. The intensities of the diffraction peaks varied according to the aging time

Effects of Gd addition on the thermal and microstructural behaviors of the as-cast Cu-9 % Al and Cu-9 % Al-10 % Mn alloys

The effects of Gd addition on the thermal and microstructural behaviors of as-cast samples of the Cu-9 % Al and Cu-9 % Al-10 % Mn alloys were investigated using different experimental techniques. The results showed that the addition of Gd does not significantly interfere in the melting and solidification temperatures of the Cu-9 % Al alloy, but it decreases the stability of beta' martensitic phase during re-heating of sample, while the presence of Mn slows the beta(A2) phase decomposition during cooling and widens its stability field. The Cu-9 % Al-10 % Mn-3 % Gd alloy has characteristics close to those observed for the Cu-9 % Al-10 % Mn alloy, but the presence of Mn increases the solubility of Gd and induces the formation of Gd-rich precipitates with average size of 200 nm.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNIFESP, Dept Ciencias Exatas & Terra, Diadema, SP, BrazilFirat Univ, Dept Phys, Fac Sci, Elazig, TurkeyDepartamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo (UNIFESP), Diadema, BrazilFAPESP: 2015/18996-0Web of Scienc