Thermal stability and brazing characteristics of Zr-Be binary amorphous filler metals for zirconium alloy

Abstract

The thermal stability and brazing characteristics of Zi-Br binary amorphous alloys as a new filler metal for joining zirconium alloy were investigated in order to supersede physically vapor-deposited (PVD) beryllium used conventionally with many disadvantages. The Zr1-xBex (0.3 less than or equal to x less than or equal to 0.5) binary amorphous alloys were produced by melt-spinning method. In the selected composition range the Zr-Be amorphous alloys have two crystallization modes which are dependent on beryllium content in alloys. The temperatures and activation energies for crystallization depend on crystallization-mode as well as beryllium content. These amorphous alloys were put into practical use in joining bearing pads on zircaloy cladding sheath. Using Zr-Be amorphous alloys as filler metals, the reduction in thickness of cladding sheath wall are prevented. Especially, in the case of using Zr0.65Be0.35 and Zr0.7Be0.3 amorphous alloys, smooth interface and spherical primary alpha-Zr particles appear in the brazed layer, which is desirable microstructure in the view of the corrosion-resistance. (C) 199S Elsevier Science B.V.