Corrosion behaviour of a rapidly solidified Al87.4Co7.9Ce4.7 layer prepared by large area electron beam irradiation

Abstract

In this study, a bulk crystalline glass forming alloy with the composition of Al87.4Co7.9Ce4.7 (at.%) was rapidly solidified by large area electron beam (LAEB) surface melting of an as-cast starting material. Glancing angle XRD results show that, providing appropriate processing parameters are selected, a predominantly amorphous layer ∼5μm thick can be produced. However, under non-optimum processing conditions treated layers are compositionally inhomogeneous and comprise, in the main, crystalline regions. LAEB treated layers also exhibit a degree of surface cracking as well as micron-sized localised craters and ejected particles formed during electron beam irradiation. Potentiodynamic polarisation tests show that treated layers exhibit enhanced corrosion resistance compared to the as-cast bulk alloy; with the predominantly amorphous layer having the lowest current density. Examination of corroded samples following potentiodynamic tests reveals that cracks limit the effectiveness of the treated layer as a barrier to corrosion.