Be-Cu joints based on amorphous alloy brazing for divertor and first wall application

The limitation on using silver-based alloys for brazing ITER in-vessel comp onents created a development problem for new brazing materials. An applicat ion of Be tiles joined to a Cu-based heat sink will be discussed in this pa per. For this purpose, rapidly solidified ribbon-type filler metal STEMET 1 108(1) (Cu-Sn-In-Ni system) with a melting temperature of 750 degrees C and a thickness up to 50 mu m was developed. A new temperature regime and heat ing method were applied during this brazing procedure. This improves the pr operties of joints significantly, in comparison with conventional brazing i n a resistance furnace. These treatments can increase the operational thres hold for Be/Cu joints under cyclic surface heat loading up to 12 MW/m(2). M etallographic examinations demonstrated the high quality of brazed joints. The brazed seam has a uniform structure along its entire length. Defects of seam filling, pores, intermetallic compounds and other inclusions are not seen. The prospects of these joints for fusion reactor applications are dis cussed. (C) 1999 Elsevier science B.V. All rights reserved.