Thermal stability and brazing characteristics of Zr 0.7−xM xBe 0.3 (M=Ti or Nb) ternary amorphous filler metals

Abstract

The effects of Ti or Nb substitution on the thermal stability and brazing characteristics of Zr 0.7− x M x Be 0.3 (M=Ti or Nb) ternary amorphous alloys were investigated in order to improve properties of Zr–Be binary amorphous alloy as a new filler metal for joining zirconium alloy. The Zr 0.7− x M x Be 0.3 (M=Ti or Nb; 0⩽ x⩽0.1) ternary amorphous alloys were produced by melt-spinning method. In the selected compositional range, the thermal stability of Zr 0.7− x Ti x Be 0.3 and Zr 0.7− x Nb x Be 0.3 amorphous alloys are improved by the substitution of titanium or niobium for zirconium. As the Ti and Nb content increases, the crystallization temperatures increase from 610°C to 717°C and 610°C to 678°C, respectively. These amorphous alloys were put into practical use in joining bearing pads on zircaloy cladding sheath. Using Zr–Ti–Be amorphous alloys as filler metals, smooth interface and spherical primary particles (proeutectic phase) appear in the brazed layer, which is the similar microstructure of using Zr 0.7Be 0.3 binary amorphous alloys. In the case of Zr–Nb–Be amorphous alloys, Ni-precipitated Zr phase that may cause some degradation in ductility and corrosion-resistance is formed at both sides of the brazed layer.