Mechanism of the effect of plastic deformation at different temperatures on the surface roughness of machined aluminum mirrors

Abstract

The existence of a coarse and non-uniform grain structure poses a substantial obstacle to achieving a decrease in surface roughness on the reflective mirror subsequent to single-point diamond turning. The grain refinement mechanism of 6061 aluminum alloy during multi-directional forging was analyzed across a temperature range from −196 °C, 25℃, to 510 °C in this study. The interrelationship between the microstructure of the aluminum alloy mirror after single-point diamond turning and its surface roughness was revealed. Dynamic recrystallization occurred at a deformation temperature of 510℃ with an average grain size of about 30um. At a deformation temperature of −196℃, more dense dislocation cells were formed along with smaller regions exhibiting different orientation differences. Additionally, as the temperature decreased, the adjacent area with poor orientation also decreased. When the range of adjacent orientation difference is less than the feed per blade, material anisotropy counteracts some mechanical response during processing resulting in an overall increase in average effect. This leads to reduced feedback response from the material to the tool and improved stability on cutting plane. Consequently, surface deviation from equilibrium surface reduced from ranging between5 and 8 nm to2-4 nm while roughness Ra decreases significantly from 13.7 nm to 1.3 nm.

Keywords

• Aluminum mirror
• Surface roughness
• Cryognic forging
• Orientation
• SPDT