Friction Behaviors And Characterization Of High Strength Aluminium Alloys

The technique of friction stir welding did prove itself ideal for creating good qualitybutt joints and lap joints of some metal which difficult to weld by conventional fusionwelding processes. It is important to understand the friction mechanism during the frictionstir welding process. In this research, we present and discuss an experimental method todetermine the coefficient of friction during FSW, at different contact pressures androtation speeds. The appearance of friction regions were observed and analyzed by usingof SEM. Simulating friction stir welding process friction behavior, investigate theevolution of the friction under different conditions and compared to the actual friction stirweld.The conclusions are as followed: In the initial friction, the coefficient of friction ofthe2024aluminum was a volatile state and over time gradually leveling off of growth. Atthe initial of the friction, the frictional mechanism of the frictional surface is mainly thedry friction and the stable stage is mainly the adhesion wear. The coefficient of frictionwas found to increase with contact pressure initially and then decreases, and fluctuatingwith the increased rotation speeds. The coefficient of friction of the7050aluminum wassmaller than2024aluminum, and in the initial stage is also mainly the dry friction then thestable stage is mainly the adhesion wear. At the low contact pressure the coefficient offriction was a volatile state and at the medium contact pressure and the high pressurefluctuated smaller. At the low rotation speeds the coefficient of friction was fluctuatedsmaller, and cyclical fluctuations in the high speed state. Under all conditions the averagecoefficient of friction of the two materials were0.3to0.6.The steep increase in the coefiicient of friction is depend on the environmental factorand the viscous flow contact state of the friction pair. From the comparative analysis of thesurface morphology of friction mark and the morphology of actual key hole after frictionstir welding, both are there the viscous flow layer, furrows honing, wear debris ofaluminum, etc. Thus it can be seen simulating the friction mechanism evolution behaviorof the friction stir welding by the experimental method is feasible.