Application and testing of SupremEX 640XA and AyontEX 13 for mirrors and precision structures

SupremEX® 640XA Al-SiC MMC and AyontEX™ 13 Al-Si alloy are advanced aluminum-based materials developed by Materion Corporation that are under consideration for mirrors and related precision structures for high performing land, sea, air, and space applications. SupremE X® 640XA is a Metal Matrix Composite (MMC) with a 6061B aluminum alloy matrix reinforced with 40vol.% ultrafine Silicon Carbide particles and is harder, lighter, and stiffer than Titanium 6Al4V with excellent fracture toughness and fatigue resistance. AyontEX™ 13 is a hypereutectic Aluminium-Silicon alloy and is both lighter and stiffer than aluminum alloy 6061-T6. Both materials also have CTEs that are well matched to that of electroless nickel plating (13ppm/°C) commonly used for mirror applications. Our investigations demonstrate that these materials can sustain requisite properties of finished mirrors operating at visible wavelengths and over broad ranges of operational temperature. A 150mm aperture finished light-weighted concave spherical test mirror was designed and manufactured according to developed manufacturing guidelines for both materials and is representative of design forms for airborne and space applications. Optical finishing operations inclded diamond point turning (DPT) and loose abrasive polishing. By use of laser interferometry, mirror figure stability was verified after multiple thermal cycles. Similar interferometric measurements were then repeated when subjecting the test mirrors to hot and cold temperature excursions under vacuum. These experiments were also performed both before and after the application of electroless nickel plating. Also considered were concepts for precision structures that are best fitted to the unique manufacturing-related characteristics of these materials.