Microstructural changes due to ion irradiation in β-CuZnAl alloys

Abstract

The {beta}-phase CuZnAl alloys undergo martensitic transformations to several close-packed structures, depending on the alloy composition. In order to study the effects of higher doses of irradiation on the phase stability in these alloys, ion irradiation experiments are now being carried out. In this work, results on microstructural changes after light and heavy ion irradiation in the {beta} phase of CuZnAl alloys followed by Transmission Electron Microscopy are reported. Single crystals of composition Cu-22.7at.%Zn-12.7at.%Al were used. At this composition, the B2 ordering temperature is about 810K, the L2{sub 1} ordering temperature is about 530K and the martensitic transformation temperature is below liquid nitrogen temperature. At room temperature, the alloy has then an L2{sub 1} long-range-ordered structure. Disks of 3mm diameter were prepared by spark erosion. In most experiments the orientation of the foil was close to (110). The samples were irradiated on one side and then back-polished from the other side to perforation, for observation in TEM. Irradiations were carried out with 300 keV Cu{sup +} ions with a flux of 5 {times} 10{sup 12} ions/cm{sup 2}s and 300 keV He{sup +} ions with a flux of 5 {times} 10{sup 13} ions/cm{sup 2}s. The dose rates, calculated using cross sectionsmore » obtained from TRIM simulations, with an average threshold energy of 25 eV, were 10{sup {minus} 2} dpa/s. for the Cu{sup +} and He{sup +} irradiations respectively. The irradiation temperature for the former was about 316K. For the later, a cooling holder was used to keep the temperature between 283K and 289K during irradiation. Before irradiation, the samples were annealed at 1,120K for 20 minutes and cooled in air to room temperature.« less