Impact of process parameters on transitions in the micro structural characteristics and mechanical attributes of titanium alloy joints during FSW

Abstract

Alloys of titanium (Ti) have been employed widely for fabricating newlineseveral aerospace components and structures, owing to their admirable newlinestructural adaptability, extreme temperature resistance, superior specific newlinestrength, exceptional resistance towards corrosion, low density etc. When newlineemployed as structural metals, alloys of titanium were usually observed to be newlineweldable by various fusion joining processes including gas metal arc and newlinetungsten arc welding, plasma arc, electron beam welding. newlineAt the same time, distortion of the welded Ti alloys by employment newlineof fusion welding methodologies normally occur owing to the low thermal newlinebased conductivity of the Ti. In addition to this, Ti and its alloys are newlineextremely reactive in their molten condition and the generation of Ti based newlineoxides, porosities, inclusions etc., in the nugget of the weld zone will certainly newlineresult in the fabrication of inferior quality Ti joints possessing degraded newlinemechanical properties. newlineMoreover, several deformities (including distortion, porosity) have newlinebeen reported w.r.t. the fusion welded joints of Ti alloys, which have been newlinefound to have occurred, owing to the inadequate thermal conductivity of newlinetitanium alloys. In addition to this, employment of fusion joining processes newlinefor welding together superior strength alloys of Ti, results in the generation of newlinecast architectures possessing coarse sized grains thereby diminishing the newlinestrength of the welded joints. Apart from this, structural components joined newlineusing fusion welding processes are not usually preferred for aerospace newlineapplications owing to the generation of brittle coarse type micro-structure and newlineexistence of severe residual category stresses in welded joints. newline newline