Microstructure and pitting behaviour of Al-Ti-Ni laser alloyed layers in 2014 aluminium alloy substrates

Amorphous aluminium alloys have received considerable interest with regard to their potential for providing enhanced corrosion properties as a result of the elimination of grain boundaries. The main conventional technique for preparation of amorphous alloys include melt spinning and sputter deposition. This paper presents work on the realisation of an amorphous layer by the laser surface alloying of a novel Al-Ti-Ni alloy into a 2014 aluminium alloy substrate. A detailed review of the scientific basis for the selection of Al-Ti-Ni as a system of interest from the point of view of the potential for the formation of amorphous layers at rates of cooling commensurate with laser surface melting with a CO2 laser is presented.The conditions required for amorphisation were investigated under different laser operating conditions. Microstructure and chemical composition of the laser alloyed layers were characterised by optical microscopy, SEM, EDAX and EPMA. The microstructures were found mainly to consist of extra-fine crystalline structures, but on the uppermost surface of the laser alloyed layer, thin glass-like layers with thickness up to 2-4 μm were formed. The various phases were identified by XRD. The electrochemical behaviour of these alloyed layers in deaerated 1M NaCl solution was determined by the use of the potentiodynamic anodic polarisation technique. The pitting corrosion behaviour was correlated with the microstructure of the laser alloyed surfaces produced. After laser treatment, a significant improvement of pitting corrosion resistance was achieved and the pitting potentials of laser alloyed layers were increased by up to 440 mV in comparison with untreated 2014 aluminium alloy substrates.Amorphous aluminium alloys have received considerable interest with regard to their potential for providing enhanced corrosion properties as a result of the elimination of grain boundaries. The main conventional technique for preparation of amorphous alloys include melt spinning and sputter deposition. This paper presents work on the realisation of an amorphous layer by the laser surface alloying of a novel Al-Ti-Ni alloy into a 2014 aluminium alloy substrate. A detailed review of the scientific basis for the selection of Al-Ti-Ni as a system of interest from the point of view of the potential for the formation of amorphous layers at rates of cooling commensurate with laser surface melting with a CO2 laser is presented.The conditions required for amorphisation were investigated under different laser operating conditions. Microstructure and chemical composition of the laser alloyed layers were characterised by optical microscopy, SEM, EDAX and EPMA. The microstructures were found mainly to consist of extra...