TIG WELDING OF ALUMINIUM BASE PARTICULATE . COMPOSITES

Abstract

Tungsten Inert Gas (GIG) welding of Al-A1203 particulate _ composites containing coarse and fine particles, has been investigated in repect of joint design, number of passes and the welding current. The.composites have been synthesized in the laboratory here by stircasting technique and the mechned plates from ingots have been used for joining in a butt joint or V-groove joint with or without filler wire by a single pass or double pass. In absence of fillers, the particles in composites containing coarse particles gets charged and eject out of the weld pool towards the nozzle often chocking it, presumably due to charging under electric field. Sometimes, the void left in the weld pool after ejection of particles, is not filled up by surrounding liquid and a cut propogates. But, the composites containing coarse particles can be welded with a filler wire of Al-Mg alloy when particle charging and ejection are relatively less, possibly due to relatively lower extant of particles in the weld pool. Presence of-particles in the weld bead contributes to a good hardness and strength and a welding current of 120A results in a satisfactory joint. On reducing or increasing the current level, the particle content in the weld bead reduces which has been attributed to lower extent of melting in base material at lower current and an enhanced particle ejection at higher current. Composites containing fine particles can •be welded. relatively easily in a butt joint without filler or in a V-groove joint with filler by a double pass, or in V-groove joint by single pass. But larger particles in the composite containing fine particles are not visible in the weld centre. These particles may have ejected out, floated out or settled down from the weld bead. The present investigation establishes that composites containing fine particles can be joined relatively easily in comparison to the composites containing coarse particles. Also, the importance of particle charging, particle settling/floatation and the extent of melting of the base material are important aspects for joining particulate composites as revealed by the current investigation.