EFFECT OF HEAT INPUT ON THE STRUCTURE AND PROPERTIES OF ALUMINIUM WELDMENT

The probable reasons for evolution of weld porosity and solidification cracking and the structure- property relationship in aluminium welds were investigated. Aluminium plates (۱xxx series) were welded by Tungsten Inert Gas (TIG) welding process, ۵۳۵۶ filler metal was used and heat input was controlled by varying welding current (۱۴۵A, ۱۷۵A and ۱۹۵A). The welded samples were examined under optical and scanning electron microscopes and mechanical tests were performed to determine tensile and impact strengths. Secondary phase, identified as globules of Mg۲Al۳ precipitates, was found to be formed. Solidification cracking appeared in the heat affected zone (HAZ) and porosities were found at the weld portion. The tendency for the formation of solidification cracking and weld porosities decreased with increased welding current.

Keywords:

Aluminium , TIG welding , welding current , secondary phase , porosity , solidification cracking