Aluminum alloy AA-6061 and RSA-6061 heat treatment for large mirror applications

Abstract

Aluminum mirrors and telescopes can be built to perform well if the material is processed correctly and can be relatively low cost and short schedule. However, the difficulty of making high quality aluminum telescopes increases as the size increases, starting with uniform heat treatment through the thickness of large mirror substrates. A risk reduction effort was started to build and test a ½ meter diameter super polished aluminum mirror. Material selection, the heat treatment process and stabilization are the first critical steps to building a successful mirror. In this study, large aluminum blanks of both conventional AA-6061 per AMS-A-22771 and RSA AA-6061 were built, heat treated and stress relieved. Both blanks were destructively tested with a cut through the thickness. Hardness measurements and tensile tests were completed. We present our results in this paper and make suggestions for modification of procedures and future work.

Impact of thermal treatment modes upon hardening stresses and properties of D16 alloy

“…Остаточные максимальные и минимальные напряжения σ мах и σ мин рассчитывали, используя следующее уравнение [4]: На рис. 5 и в табл.…”

“…Восходящая закалка может быть применена для ряда высокоточных фасонных крупногабаритных изделий, например полых профилей, в частности труб [16], вафельных конструкций, рамок инерционных систем позиционирования, крупногабаритных зеркал телескопов [4] и т.д.…”

Advanced techniques for robotic polishing of aluminum mirrors

“…In recent years, post-polishing has been applied in many applications to improve surface roughness and form of diamond turned surfaces -mainly plano optics and some aspheric surfaces. In practice, results have been limited by the material and slurry properties [8]. Due to the softness of aluminum, typical issues that arise in mechanical lapping and polishing, are smearing of the metal surface, and embedding of the abrasive material [1,12].…”

“…In optical application, these can produce diffractive side-lobes to images, and random scattered light, reducing detected signal-tonoise ratio. Wavelengths shorter than the infrared, and stray-light sensitive applications, often require surfaces superior to what SPDT alone can usually deliver [8]. As a general point, MSFs can also impact performance in non-optical applications.…”

Finishing of metal optics by ion beam technologies

“…Technical aluminum alloy materials, such as AL6061, show an excellent shape stability, which is necessary for robust and durable optical devices. 1,2 Optical aluminum surfaces for use in the infrared spectral range are usually fabricated by single-point diamond turning (SPDT). [3][4][5] However, for short-wavelength applications in the visible (VIS) or even the ultraviolet (UV) range, the requirements on the optical surface quality increase.…”