Titanium Diffusion And Phase Formation In Tube-Type Rod-In-Tube And Internal-Tin Nb3sn Strands

The influence of Ti on phase formation in both rod-in-tube (RIT) and "tube-type" Nb3Sn strands has been explored. Two RIT subelement billets and three tube-type subelements were prepared. In one of the RIT subelements and one of the tube-type subelements the Sn source was alloyed with Ti, otherwise the core was of unalloyed Sn. After drawing to final size the strands were reacted according to a typical schedule consisting of. (i) ramp at 10 degrees C/h to 185 degrees C, hold 24 h, (ii) ramp at 25 degrees C/h to 340 degrees C, hold 48 h, (iii) ramp at 10 degrees C/h to 650 degrees C, hold to various times. After a sequenced of holding times, the samples were quenched to retain the high temperature phases, enabling the formation of the various Nb-, Cu-, Sn-, Ta-, and Ti-containing phases to be studied by SEM and EDS. The results were compared with predictions based on the Cu-Sn and Nb-Cu-Sn phase diagrams.