Temperature Dependence of Amorphization above 10K in the CuTi Intermetallic Compound Under Electron Irradiation
- PDF / 431,567 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 33 Downloads / 205 Views
TEMPERATURE DEPENDENCE OF AMORPHIZATION ABOVE 10K IN THE CuTi INTERMETALLIC COMPOUND UNDER ELECTRON IRRADIATION J. KOIKE*,
D. E. LUZZI*, M. MESHII* and P. R. OKAMOTO**
Department of Materials Science and Engineering, Northwestern University, Evanston, IL. 60201 ** Materials Science and Technology Division, Argonne National Laboratory, Argonne, IL. 60439 *
ABSTRACT The critical dose required to amorphize the crystalline compound CuTi during irradiation with 1 MeV electrons has been investigated from 10 to 288 K. The results show that above a critical temperature (Tc) of about 185 K, CuTi remains crystalline and only defect clusters are formed. The Below Tc, amorphization occurs with no observable cluster formation. critical dose for amorphization was found to be temperature dependent as the irradiation temperature increases, a higher dose is below Tc: This observation supports the concept required to induce amorphization. Below Tc, that Tc corresponds to the vacancy migration temperature. interstitial migration may contribute to the observed reduction in the amorphization rate with increasing temperature. INTRODUCTION The amorphization of intermetallic compounds under electron irradiation has been studied in many compounds since Thomas et al. (1) first reported Empirical correlations have been found between the phenomenon in NiTi. certain properties of intermetallic compounds and their tendency to Although the amorphization mechanism is amorphize during irradiation (2). not well understood, it is commonly observed (3-5) that those compounds which become amorphous during electron irradiation do so only below some This temperature has been widely regarded as critical temperature (Tc). the temperature above which a point defect becomes mobile and some kinetic A models (6,7) assume that this point defect is an interstitial type. prediction of these models is that below Tc the critical dose for In the present paper, amorphization should be independent of temperature. we report the results of an investigation which shows that the critical dose for CuTi increases with temperature, supporting the idea that the critical temperature (Tc) should be regarded as the temperature for the onset of vacancy migration. EXPERIMENTAL PROCEDURE An alloy button with a nominal composition of Cu4 6 Ti 5 4 was prepared by It arc-melting and was subsequently annealed at about 1170K for 3 days. The was then sliced and thinned with a double sided jet polisher. composition of the examined alloys was in the two phase region of CuTi and The intermetallic compound CuTi 2 in the equilibrium phase diagram (8). derivative of the bcc structure involving two unit CuTi is an ordered cells stacked in the direction in which two (001) layers of Cu, one displaced relative to the other by (a+b)/2, are followed by two similarly This ordered arrangement of the bcc structure in displaced Ti layers. which pairs of ordered layers of the two components alternate can be compared to the CsCl structure where single ordered layers of the two CuTi samples were irradi
Data Loading...
