GRAIN-BOUNDARY DIFFUSION OF CHROMIUM IN NI3AL INTERMETALLIC MODIFIED BY FE, CR AND ZR

Tracer grain-boundary diffusion (GBD) of chromium Cr-51 in slightly hy postoichiometric (x(Al)< 25 at%) Nl(3)Al alloys containing several at. pct of Fe, Cr and Zr was studied using both serial sectioning and res idual activity methods. Measurements of the product of the diffusion c oefficient in grain boundary and the width of grain boundary, P, were carried out in the temperature interval from 773 to 1273 K. It was fou nd that the addition of Fe and Cr up to about 6 at% does not alter the diffusion characteristics of Cr grain-boundary diffusion. The additio n of a small amount of Zr, on the other hand, tends to increase the ac tivation enthalpy and pre-exponential factor of Cr grain-boundary diff usion. (C) 1998 Published by Elsevier Science Limited. All rights rese rved.