STUDIES ON WELD METAL CHARACTERISTICS AND THEIR INFLUENCE ON TENSILE AND FATIGUE PROPERTIES OF PULSED-CURRENT GMA WELDED AL-ZN-MG ALLOY

Pulsed-current GMA welding of an extruded section of Ai-Zn-Mg alloy (7 005) was carried out by using A-lMg (5183) welding wire. During weldin g, the pulse parameters, such as pulse frequency and duration, were va ried and their effects on the zinc pickup due to dilution of base mate rial, porosity content and microstructure, as well as the hardness, te nsile and fatigue properties of the weld metal were studied. The zinc pickup of the weld was correlated to its hardness and both the zinc pi ckup and porosity content of the weld were correlated to the tensile s trength and fatigue life of the weld. The characteristics and mechanic al properties of the pulsed-current GMA weld were compared with those of a continuous-current weld. it was observed that the variation in th e pulse parameters affects the zinc pickup, Porosity content and micro structure of the weld. The increase in zinc pickup enhanced the hardne ss, tensile strength and fatigue life, whereas, the porosity content w as found to reduce the tensile strength and fatigue life of the weld. The pulsed-current GMA welding was found to improve the weld propertie s over those of continuous-current GMA welds.