INTERDIFFUSION IN THE INTERMETALLIC COMPOUND BETA-AGMG

Interdiffusion coefficients, (D) over tilde, in the beta-AgMg phase fr om 42 to 52 at% Mg have been determined by Matano's method in the temp erature range between 723 and 973 K with semi-infinite couples consist ing of beta-AgMg alloys. (D) over tilde decreases with increase of the liquidus temperature and shows a minimum at 47 at% Mg which deviates slightly from the stoichiometric composition. (D) over tilde is about one order of magnitude larger than the self-diffusion coefficient of s ilver in the whole concentration range of the beta-AgMg phase. This di fference can be attributed to the large thermodynamic factor for inter diffusion in the beta-AgMg phase. The activation energy for the interd iffusion is nearly equal to that for the self-diffusion of silver, whi le the pre-exponential factor for the interdiffusion is about one orde r of magnitude larger than that for the self-diffusion of silver in th e beta-AgMg phase.