Thermodynamic and crystallographic properties of gamma radiated shape memory Cu-Al-Be alloy

Abstract

The effect of the different doses of gamma irradiation on Cu-23.36Al-2.78Be (at.%) shape memory alloy (SMA) has been investigated in this study. The effect of irradiated dose on characteristic transition temperatures was determined by differential scanning calorimetry (DSC). The diffraction planes which depend on irradiation dose were analyzed by X-ray diffraction (XRD), and crystallite size was calculated for alloy samples. In order to observe changes in the structure with increasing irradiation dose, optical microscope investigations were performed. The transformation temperatures and activation energies decreased after irradiation, and some changes occurred in the forming latent gas. The sample of the heat treated but unirradiated alloy includes the beta (DO3) structure as matrix phase at room temperature. With increasing irradiation dose, 18 R martensite structure is observed. Microhardness values and crystallite size values of the alloy samples changed significantly with increasing irradiation dose. The average crystallite size was found as 42.99 x 10(3) +/- 18.71 nm for Cu-23.36Al-2.78Be (at.%) SMA. The thermal measurements showed a non-monotonous change on transition temperatures by the increase in applied dose value. Radiation hardening is about the beginning of spot defects in the metal structure. The basis of the mechanism is the interaction of the defects with movement of dislocations. Under the effect of radiation, very fast moving atomic particles strike the atoms that make up the crystal structure and force them out of their balanced position. As a result, atomic cavities and some defect atoms are formed in the lattice because of the gamma radiation.