Effect of FSW Procedure on the Time-Evolution of the Properties in AA 7075-T651 Joints

• Published in: Soldagem & Inspeção Vol. 19; no. 4; pp. 333 - 342
• Main Authors: Tufaro, Leonardo N, Svoboda, Hernan G
• Format: Journal Article
• Language: Portuguese
• Published: 01.12.2014
• Subjects: Aluminum base alloys; Evolution; Friction stir welding; Heat affected zone; Inspection; Tensile strength; Welded joints; Welding
• ISSN: 0104-9224; 1980-6973
• DOI: 10.1590/0104-9224/SI1904.06

It was studied the effect of the welding procedure on the temporal evolution of the mechanical properties in AA 7075-T651 friction stir welded joints. To vary the heat input samples with different parameters (rotation and welding speed) were welded. Thermal cycles were acquired by means of thermocouples instrumented on the samples, obtaining the heat input for each case. The welded joints were macrostructural characterized using optical microscopy. Vickers microhardness profiles and tensile tests were measured for different times after welding (between land 900 days). The minimum hardness (HV sub(min)) value was located in the heat affected zone (HAZ). That HV sub(min) decreased with heat input and was increased with the time elapsed after welding showing a logarithmic relationship, for the different welding conditions analyzed. This HV sub(min) increasing was higher for the sample welded with the lower heat input. Tensile strength of welded joints increased with the time after welding, according to a logarithmic relation too, reaching an joint efficiency of 80%.Original Abstract: Se estudio el efecto del procedimiento de soldadura sobre la evolucion temporal de las propiedades mecanicas de uniones soldadas por friccion-agitacion (FSW) en chapa de AA7075-T651. A este fin se realizaron soldaduras por FSW bajo distintas condiciones de soldadura (velocidad de rotacion y velocidad de avance) de modo de variar el aporte termico. Se registraron los ciclos termicos mediante la instrumentacion de termocuplas y se determino el aporte termico neto en cada caso. Las uniones soldadas fueron caracterizadas macroestructuralmente, se determinaron perfiles de microdureza Vickers y la resistencia a la traccion a distintos tiempos luego de realizada la soldadura, los cuales variaron entre 1 y 900 dias. Se observo que la dureza minima (HV sub(min)) se ubico en la zona afectada termicamente (HAZ) y que la misma aumento al disminuir el aporte termico introducido durante la soldadura. Asimismo, dicho valor HV sub(min) aumento con el tiempo, siguiendo una evolucion logaritmica para todas las condiciones de soldadura. Este aumento fue mayor para la probeta soldada con menor aporte termico. A su vez, la resistencia a la traccion de las uniones soldadas aumento con el tiempo, evolucionando tambien en forma logaritmica, alcanzando una eficiencia de junta del 80%.