Precipitation Strengthening and Corrosion Behaviour of a 6061 Al-Mg-Si-Cu Alloy (Pages 29-38)
Department of Metallurgical and Materials Engineering, National Institute of Technology, Durgapur – 713 209, India
Abstract: Precipitation strengthening, behaviour of a 6061 Al-Mg-Si alloy tempers has been assessed by hardness measurement, X-ray diffraction (XRD), and optical microscopy. Variation of hardness with precipitation time of the alloy solutionised and water quenched state indicated characteristic age strengthening, behaviour. Electrochemical behaviour of the alloy of different tempers was assessed by potentiodynamic polarization studies in 3.5 wt. % NaCl solution (~ pH 7) and in 3.5 wt. % NaCl at pH 12. Polarization diagrams showed shifting of corrosion potential (Ecorr) towards more negative potential with increasing precipitation time. Cyclic polarization diagrams at 3.5 wt. % NaCl at pH 12 exhibited distinct passivity phenomenon. Optical micrographs of the corroded surfaces showed general corrosion and extensive pitting corrosion as well.
Keywords: 6061 Al-Mg-Si-Cu alloy, Precipitation strengthening, Electrochemical polarization, Passivity, Hysteresis loop.