Effect of the surface roughness of friction stir welded joints on the fatigue characteristics of welded joints in V-1461 and V-1469 aluminium–lithium alloys

Abstract

Investigations were carried out into the effect of friction stir welding conditions of V-1461 and V-1469 aluminium–lithium alloys on surface roughness and mechanical properties of welded joints. The general parameter of the welding conditions was the heat input coefficient determined by the ratio of the speed of rotation of the tool to the welding speed. The optimum range of friction stir welding conditions of sheets of the investigated alloys was determined. In this stage, the surface finish of the welded joint after welding is much better (required for increasing the fatigue characteristics and high-quality deposition of protective coatings), there are no defects and the strength of the welded joint is equal to 0.75–0.85 of the strength of the parent material. The production of the welded joints with reduced surface roughness (Rz ≤ 40 μm) greatly increases the fatigue characteristics of the welded joints (low-cycle fatigue strength equals more than 300,000 cycles without fracture).