FATIGUE BEHAVIOR OF HIGH STRENGTH AL-CU-MG AND AL-CU-LI ALLOYS JOINTS OBTAINED BY FUSION AND SOLID STATE WELDING TECHNOLOGIES

This paper presents analyses of strength characteristics and fatigue behavior of butt welded joints of 2mm thickness high strength D16T1 (Al-Cu-Mg) and 1460T1 (Al-Cu-Li) aluminum alloys, produced by tungsten inert gas (TIG) welding and friction stir welding (FSW). It is shown that friction stir welded joints has minimal stress concentrations in places of transition from the weld to the base material and also have no defects in the joint such as oxide film macroinclusions and hot cracks caused by melting and crystallization of the metal in fusion welding. At that, severe plastic deformations of metal under tool shoulder and in weld core results in formation of fine grain (3-4 mu m), homogeneous disoriented structure and elongation and deviation of grains in a direction of plasticized metal movement take place in adjacent areas. Consequently, hardness and tensile strength of the joint weld metal are increased. Fatigue behavior under constant amplitude loading of FSW joints exceeds the characteristics of the joints obtained by TIG welding.