Electrical Resistivity and Positron Lifetime Studies of Precipitation Effects in Al-Cu Alloy |
| P. Αda, M. Cieslar, P. Vostrý, F. Bečvář, I. Νovotný and I. Procházka Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic |
| Full Text PDF |
| Decomposition of the supersaturated solid solution of 2 at.% Cu in Al was investigated by means of electrical resistivity and high-resolution positron lifetime measurements. The phase composition of this alloy was determined by transmission electron microscopy. Electrical resistivity measurements were performed by a classical four-point method. Positron lifetime spectra were measured by means of a spectrometer consisting of two BaF2 detectors and a standard fast-slow coincidence system. The specimens were first exposed to the solution heat treatment at 783 K for 19 hours with a subsequent quenching. Then the specimens were isochronally annealed in the temperature range 293 ÷ 573 K. Annealing responses of electrical resistivity and positron annihilation were studied. Resistivity measurements as well as transmission electron microscopy observations confirmed the well-known decomposition sequence of the Al-Cu alloy. The decomposition of the alloy was manifested by the decrease in the intensity of positron lifetime component τ2 = (207 ±2 ) ps correlated with simultaneous appearance and increase in the intensity of τ3 = (180 ± 5) ps component. Component τ2 originates from positron annihilation in vacancies trapped at the Guinier-Preston zones while τ3 comes from annihilation of the positrons localized in the misfit dislocations at coherent precipitates of the Al2Cu phase. The shortest observed component τ1 apparently belongs to annihilation of untrapped positrons. |
| DOI: 10.12693/APhysPolA.88.111 PACS numbers: 61.72.-y, 78.70.-g, 81.40.-z |