Influence of defects in the aluminium alloy Al6061 on the diffraction effect of diamond turned optics

Abstract

Aluminium alloy Al6061 is one of the most popular materials for the fabrication of reflective optics. To reveal the influence of material defects in Al6061 on the diffraction effect of diamond turned optics, simulations are performed on a well-established surface topography model. The results indicate that for the defects with similar size parameters in the x- and y-axis direction, e.g. grain boundary, hard inclusion protrusion and void, they are responsible for the diffracted light spots on the whole receiving screen. The scratch on the machined surface mainly affects the diffracted light spots in the horizontal direction; and its influencing pattern is similar to the turning mark. The influence of oxide film on the diffracted light distribution is rather limited due to its uniform property and small thickness on the ambient environment. The simulation and experiment results indicate that the diffraction efficiency of the specular light obviously decreases with the increase of the defect size in the work material matrix.