Joining behaviour of crystalline and amorphous Zr-based alloy using Cu-based braze

Chiu, Yen-Lin (2014). Joining behaviour of crystalline and amorphous Zr-based alloy using Cu-based braze. University of Birmingham. M.Phil.

Preview

Chiu14M.Phil.pdf
PDF - Accepted Version
Download (11MB)

Abstract

The objective of this research was to understand the melting and wetting behaviour of braze alloys and mechanical properties of brazed joints for pure zirconium plates and the Zr-based bulk metallic glass (BMG), Vitreloy 105 (Zr $_5$ $_2$ $_.$ $_5$ Cu $_1$ $_7$ . $_9$ Ni $_1$ $_4$ $_.$ $_6$ Al $_1$ $_0$ Ti $_5$ ). Active brazing alloy, Cusil ABA (Ag $_6$ $_3$ Cu $_3$ $_5$ $_.$ $_2$ $_3$ Ti $_1$ $_.$ $_7$ $_5$ ), has been used to braze Zr plates in the Gleeble 3500 thermo- mechanical simulator under vacuum at 3 temperatures (840, 940 and 1000 $^o$ C) and with Vitreloy105 at 780 $^o$ C. The shear strength of the brazed Zr-plate increased at lower brazing temperatures; brazing of Vitreloy 105 plates was not successful as the brazing temperature, (Cusil ABA liquidus temperature) exceeded its crystallisation temperature Tx=440 $^o$ C leading to crystallization and embrittlement during to brazing. As a result, three BMG compositions (Mg $_6$ $_5$ Cu $_1$ $_5$ Ag $_1$ $_0$ Tb $_1$ $_0$ $_,$ Zn $_4$ $_0$ Mg $_1$ $_1$ Ca $_3$ $_1$ Yb $_1$ $_8$ and Ca $_6$ $_5$ Mg $_1$ $_5$ Zn $_2$ $_0$ ) as potential brazes for Vitreloy 105 with liquidus temperatures below the crystallisation temperature and high values of fracture strength have been selected to predict (using Thermo- Calc) the equilibrium reaction between substrate and braze prior to manufacture in order to estimate likely wettability and joint strength.