Ultraprecision diamond turning of mechanically modified Al-Mg alloy for diffraction optical elements

Single-point diamond turning (SPDT) is a critical technique in the ultraprecision manufacturing of optical components, offering nanometric surface finishes and submicron form accuracy. However, the influence of material strengthening, particularly through cold working on surface integrity and machining efficiency remains insufficiently understood. This study investigates the effects of feed rate and mechanical conditioning on surface finish and cutting forces during SPDT of an Al–Mg alloy subjected to varying degrees of cold rolling (50% and 90% thickness reduction), compared to the annealed condition. Mechanical properties were characterized through microhardness and elastic recovery measurements, while surface integrity was evaluated using roughness parameters (Rt and Sdq). Cutting forces were recorded in situ to assess energy consumption. The results reveal that increased work hardening leads to higher cutting forces, especially at high feed rates and increased specific cutting energy at low feed conditions. Despite enhanced strength and reduced anisotropy, cold rolling was found to adversely affect surface finish due to intensified tool–material interactions and elastic recovery. These findings highlight the complex interplay between material microstructure and machining parameters in achieving optimal performance in ultraprecision manufacturing diffraction optical elements.