Almeida, M Anjos, R Vilar, R Li, M G S Ferreira, K G Watkins,
microstructure and corrosion resistance of laser-alloyed
aluminium and ANSI 7175 aluminium alloy with chromium
were investigated. Surface layers alloyed with chromium
contain relatively large amounts of intermetallic compounds
dispersed in a matrix of a-Al. The intermetallic compound
particles present needle-like morphologies, organized
in a dense network or distributed radially. Al7Cr, Al11Cr2
and a-Al phases have been identified by X-ray diffraction.
The alloyed layers may contain cracks, pores, inclusions
and undissolved chromium particles, depending on the chromium
concentration and particle size. However, homogeneous
layers were produced by a two-step process, consisting
of laser alloying followed by remelting. The second treatment
eliminates porosity and refines the structure. The hardness
attains a Vickers hardness of 155 HV in chromium-alloyed
aluminium and exceeds 300 HV in chromium-alloyed 7175.
The corrosion behaviour of the above alloys was assessed
using anodic polarization techniques. Laser alloying of
aluminium and 7175 with chromium improves the pitting
corrosion resistance of the alloys. The effect depends
on the chromium content of the alloyed layers and is more
significant in 7175 alloy.