OXIDATION AND HYDROGEN BEHAVIUR IN Zr-2Mn ALLOY

The purpose of the present research was to determine the oxidation and hydrogenation behavior in the new Zr2Mn alloy. The oxidation of alloy was performed at temperatures between 350 degrees C and 900 degrees C for 30 minutes. The hydrogen charging was made for 72 h at a current density 80 mA/cm(2). The charged samples were heat treated at 400 degrees C for 4 h to obtain a uniform hydrogen profile content across the sample. The oxidation resulted in an appearance of non-uniform oxide layers of thickness increasing with temperature. The surface damage was observed at higher temperatures 700 and 900 degrees C. After charging with hydrogen followed by annealing no hydrides were found. The observed effect is evidence that the oxide layers may form effective barriers against hydrogen diffusion even if they are partially degraded. The absence of hydrides or hydride cracking may be caused by an absence in Zr-Mn alloys of such phase precipitates, which may trap diffusive hydrogen and initiate the hydrides. The positive influence of manganese on the formation of the thick oxide layer and relative resistance to delayed hydride cracking may be attributed to its affinity of oxygen, the ability to form thick and compact oxide layers during oxidation, the formation of solid solution in zirconium and no precipitates enhancing nucleation of hydrides.