CHARACTERIZATION OF WELDABIL.ITY - OF SCANDIUM INOCULATED Al'Zn-Mg ALLOY

Abstract

The high strength aluminum alloys hold significant share in the worldwide usage of light alloys. The Al-Zn-Mg alloys in particular which come under the 7xxx series of aluminum alloys have special high strength characteristics. Their usage in construction of light armored vehicles, light weight bridges, and other components like fuselage in fighter crafts which demand for high strength to weight ratio, have earned these alloys a special recognition among the light alloys. Although, they have the highest mechanical properties among all the aluminum alloys and provide superior ballistic protection, they suffer few drawbacks especially in terms of welding. The material has stress corrosion cracking issues in both parent metal and weld joint. ,Most of the industries prefer cost effective conventional welding processes like GTAW and GMAW for the purpose of welding these alloys. The variant of the GMAW process in which pulse current is used, also called Pulse GMAW process, have been reported to successfully weld these alloys. In the present work, the characterization of the weldability of Al-Zn-Mg alloys by making alloy modification i.e. Scandium inoculation and controlling the pulse parameters of the pulse GMAW process was attempted in order to improve the properties in terms of metallurgical and mechanical context, especially in the weld zone and the adjacent HAZ. Different parameters like voltage, peak current, pulse on time, frequency, heat input etc were suitably chosen and then executed on the forged cum heat treated material. The metallurgical as well as mechanical properties were studied by analyzing the weld specimens through standard testing and measurement solutions viz. microstructure analysis, weld geometry analysis, weld dilution analysis, porosity analysis, hardness measurement, etc. Critical reasoning and analysis of the results was done in order to achieve the objective of characterization of weldability of Sc inoculated Al-Zn-Mg alloy.