Intermetallic Co-Al powder for nuclear applications

Intermetallic compounds based on the Al-Co system were synthesized by solid state method - mechanical alloying and their properties were investigated using XRD, SEM, and DSC. The powder was used to make new targets of irradiation for gamma sources in order to enhance the specific activity and to reduce the consumption of material. The intermetallic compound AlCo was formed in the first 4 hours of milling. After 8 hours of milling the medium size of crystallites were of 5.58 nm. This value decreases with the increase of milling time up to 3 nm, corresponding to the 28 hours of grinding. There was calculated and plotted the Gibbs function, Δf0, for the reaction of formation AlCo and Al3Co from the Al-Co system. It had negative values over the entire range of temperatures for both investigated compounds. After 28 hours milling a phase composition was obtained as follows: 0.2% Al; 21%Co ; 55.5%AlCo; 23.3% Al13Co4. AlCo 98% has been obtained after a treatment of the powder at 1200 deg. C. The final phase composition of the powder was as follows: 0.2% Al ; 1%Co; 97.5%AlCo;1.3 % Al13Co4 . Determined were the variation of grain size, microtensions II and dislocation density during the milling process. (authors)