Development of Al [sbnd]Ge base rheocast brazing alloys

Abstract

This study concerns the development of an aluminium—germanium rheocast brazing alloy able to join replaceable sacrificial protections onto permanently cooled substrates in the ITER divertor. The rheocast alloy must be solid at the in-service temperature (up to 350°C) and semi-solid, with a viscosity close to that of grease, in a wide range of temperature above: this last property will allow the in-situ replacement of the sacrificial components even on vertical surfaces. This paper describes the fabrication route of the rheocast and reports the mechanical characterisation both up to 400°C and in the semi-solid region. Moreover, the brazing process has been optimized to obtain sound joints. The surface, mechanical resistance and thermal stability of the Al Ge/Cu joint are presented. Successive brazing tests have been performed to show the feasibility to sacrificial parts removal and replacement.