Processing and characterisation of Ag-Cu- Ti brazing alloys

Abstract

Silver based brazing alloys having compositions or Ag : Cu :: 72:28. 50:50 and 30:70 by Wt%. and with varying amount of active clement. Ti. (I-3 Wt%.) were prepared. The samples were characterized by SEM. EDX and XRD to study the phase formation and morphology in the system. The XRD pattern could not able to reveal the Ti, related phases due to low amount or Ti, In the present system under investigation. Scanning Electron Microscopic images have shown that two types of phases (copper rich -dark and silver rich - bright phase) are present in the samples. The EDX analysis also reveals that with the increase of titanium addition. Ti content increases within the copper rich (dark) phases. Image analysis was also carried out to find the volume fraction of silver and copper rich grains. The increase or melting temperature at which Ti was added and the copper content, has found to play a significant role in determining the final Ti content in the alloy. For low copper alloy, it is difficult to incorporate titanium in the alloy due to low solubility or titanium in silver rich phase. In the case or alloy 3% Ti can easily be incorporated and for 30:70 alloy the Ti incorporation is reduced. The high alloying temperature (1000-I025oC) of the 30:70 alloy increases the titanium-carbon reactivity resulting in the reduction or titanium content in the final alloy. Therefore 50:50 Ag-Cu base alloy has been found to be ideal for the incorporation or maximum amount or titanium. No Ti loss is observed in the alloy when 3 wt% Ti is added. In this alloy the dark phase contains ~6.8 wt% and in the bright phase only ~0.3 wt% Ti is observed.