Determination of displacement threshold energies in pure Ti and in gamma-TiAl alloys by electron irradiation

Resistivity damage rates, determined during low-temperature electron irradi ations in the energy range 0.3-2.5 MeV, were used for evaluating displaceme nt threshold energies of titanium in high purity hcp titanium, and of titan ium and aluminium in gamma-TiAl intermetallic compounds. These parameters w ere deduced from a comparison of experimental displacement cross-section va riations as a function of electron energy, with theoretical curves based on a displacement model for diatomic materials. The displacement energy of ti tanium in hcp titanium appears to depend on the electron energy. A threshol d value of 21 +/- 1 eV was obtained in the range 0.3-0.5 MeV, and a larger value of 30 +/- 2 eV is determined in the range 0.5-2.5 MeV. In gamma-TiAl, aluminium atoms are displaced first, with a threshold displacement energy (34 +/- 2 eV) larger than the one of titanium atoms, and much higher than t he value in pure aluminium. The displacement energy of Ti atoms is 28 +/- 2 eV, close to the one obtained in pure titanium under similar conditions. T hese results were used for re-evaluating the Frenkel-pair resistivity of th e stoichiometric TiAl compound. (C) 1999 Published by Elsevier Science B.V. All rights reserved.