The influence of work roll roughness on the surface/near-surface microstructure evolution of hot rolled aluminum–magnesium alloys

The effect of work roll roughness on the surface/near-surface evolution of aluminum alloys during hot rolling was examined with the use of a rolling tribo-simulator. Work rolls made of steel alloy AISI 52100 with two different surface roughness (Ra) values, 0.1 μm and 1.1 μm, were used to hot roll Al-Mg alloy samples under similar laboratory conditions for one and ten passes. Surface features on both rolled samples included cracks, grooves, and rolling ridges, but shingles were only observed on the samples rolled with the rougher work roll. Near-surface damage was observed to increase with work roll roughness. Cross-sectional examinations revealed that transverse micro-cracks on the sample rolled with the smoother work roll extended to depths of 2.8 μm, while cracks were 3.2 μm in depth for the rougher work roll. In addition, the oxide-rich near-surface layers formed on the samples were thicker and more discontinuous for the rougher work roll. The oxide distribution in the transverse direction could be correlated to the size of the rolling ridges, which were larger for the samples rolled with the rougher work roll. A critical work roll surface roughness was proposed to influence the initiation of shingles on the aluminum alloy surfaces. The extent of the near-surface damage and the surface features formed on the rolled aluminum alloys were shown to be dependent on, but not limited to, the work roll surface topography.