Dissolution and precipitation behaviors of hydrides in N18, Zry-4 and M5 alloys

摘要

The terminal solid solubilities of hydrides dissolution (TSSD) during heatup and precipitation (TSSP) during cooldown for N18, Zry-4 and M5 alloys with hydrogen concentrations of 20-240 ppm were measured by differential scanning calorimetry (DSC) in the range of 50-500 ℃. There is little difference in either TSSD or TSSP solvi among these alloys, and best-fit equations were derived from the two solvi. A significant hysteresis between the solvi of TSSD and TSSP occurred, resulting from the hydride-matrix volumetric misfit strain. Based on the widths of the DSC peaks obtained during cooldown, the average precipitation rates of zirconium hydrides from the super-saturated state were evaluated by best-fit equations. The hydride precipitation is rate-controlled by hydrogen diffusion, and the average rates increased with increasing temperature.