Influence of Lathe Rotation and Secondary Dendritic Arm Spacing on Surface Roughness of an Al-3wt.%Si Alloy Submitted to the Necking Process

This experimental study aims to analyze the influence of lathe rotation and secondary dendritic arm spacing, λ2, on the surface roughness (arithmetic mean deviation of the surface height from the mean line through the profile, Ra) of an Al3wt.%Si alloy. The samples were obtained by horizontal directional solidification under unsteady heat flow conditions and subsequent necking of the ingot at defined positions from the metal / mold Interface. The roughness analysis was performed using optical microscopy. The results showed that, for all rotations, the roughness variation as a function of the secondary dendritic spacing can be expressed by experimental power function given by Ra= a (λ2 )b , where a and b are constants. It was also observed that, for the same secondary dendritic arm spacing, lower roughness values were obtained for higher rotations.