Surface Figure Stability of AlSi10Mg Mirrors Produced by Additive Manufacturing

Additive manufacturing of AlSi10Mg mirrors has attracted increasing attention owing to its advantages in weight reduction and strength improvement. However, the inherent characteristics of additive manufacturing lead to relatively high residual stress within the mirror, potentially deteriorating its surface-figure accuracy in service. Heat treatment is an effective method for eliminating residual stress, but most of the existing literature focuses on changes in the mechanical properties of AlSi10Mg after heat treatment, such as hardness and strength. In this study, two methods, artificial aging and T6, were utilized for stress-relieving heat treatment on additively manufactured AlSi10Mg mirrors, and the surface figures were characterized before and after heat treatment. When the change in the surface root mean square value is less than 0.05 λ (λ = 632.8 nm), the residual stress of the mirror is considered to have been eliminated, and the surface figures are stable. The results show that artificial aging alone cannot effectively eliminate residual stress, whereas AlSi10Mg mirrors treated by T6 can achieve a stable surface figure. Further, due to the high temperature of T6, the grains become coarse, and a high-quality surface cannot be obtained.