Characteristics of Alsi9mg/2017A Aluminum Alloys Friction Stir Welded with Offset Welding Line and Root-Side Heating/ Charakterystyka Stopów Aluminium Alsi9mg/2017A Zgrzewanych Metodą Friction Stir Welding Z Przesunięcem Linii Zgrzewania I Dodatkowym Źródłem Ciepła Od Strony Grani

Abstract

Abstract Welding of materials differing significantly in terms of chemical composition and microstructure is one of the main advantages of the Friction Stir Welding method. This paper presents the results of welding of a cast AlSi9Mg (hypoeutectic silumin) and 2017A aluminum alloys. The welding was performed with a high linear velocity (over 1 m/min). The modification of the process consisted in offsetting the welding line toward the advancing side, and in on application of an additional heat source from the root side. The study of the macrostructure (with high resolution of the image) revealed the presence of defects in the weld, despite greater plasticity of the material results from raising the temperature. The analysis (by SEM, SEM-EDS) of constituent stable phases within the cast alloy, showed their considerable fragmentation, however to a various degree. The material above the weld nugget was not mixed and contained micro-defects that did not result from the welding. The hardness distribution within the weld nugget, reveals slight strengthening of the both cast and wrought alloys. A metastable state of the 2017A alloy was also documented, however, the alloy hardness increased within the weld nugget due to the natural aging. On the other hand, the hardness of the heat-affected zone in this alloy does not increase also due to the natural aging.