THE PROMONOTECTOID REGION OF THE NB-ZR SYSTEM

The promonotectoid region of the Zr-Nb binary system has been re-evalu ated for a series of high purity alloys. The analytical electron micro scopy and measurements of the volume fractions were applied to determi ne the composition of the retained beta Zr phase. The experimental res ults were compared with the calculated phase diagram published in the literature and an excellent agreement has been found. The role of Fe p resent in these alloys as an impurity at ppm level has also been inves tigated. Iron has been found to have a systematic effect on the phase equilibria in the promonotectoid region of the diagram, consistent wit h its role as a beta-stabilizing element in Zr alloys.