EFFECT OF PEAK-AGED HEAT TREATMENT ON CORROSION BEHAVIOR OF THE AA6063 ALLOY CONTAINING Al_3Ti

摘要

The purpose of this study is to analyse the microstructure and corrosion properties of homogenised and aged A A 6063 aluminium alloys, containing up to 2% Ti, after the conventional casting technique. The microstructure of the homogenised and aged alloys was examined using an optic microscope, and scanning electron microscope. The micro-hardness test was used for the hardness measurements of the investigated alloys. Corrosion tests were performed by suspending samples of certain sizes into 30 gr/l NaCl + 10 ml/l HCl solutions, measuring the mass loss; potenliodynamic polarisation measurements were carried out in the same solution. The microstructure characterization of the investigated alloys shows the Al (matrix), non-shaped dark globular grey-coloured phase and rod-shaped phases formed at the grain boundaries. The non-shaped dark grey-coloured phase is Mg_2Si. The rod-shaped phase, formed in the microstructure of the Ti-added AA 6063 alloys, is Al_3Ti. The Ti content of the alloy increases, the Al_3Ti phase tends to elongate and become plated. The results of the corrosion tests proved that the corrosion rate decreased in alloys containing less than 1% Ti, and the rate of corrosion increased in alloys containing more than 1% Ti, regardless of whether the alloys were homogenised and aged. Another observation was that aging heat treatment improved corrosion resistance.