René 41 is a nickel-based high temperature alloy developed by General Electric which retains high strength in the 1200/1800°F (649/982°C) temperature range. It is used in jet engine and missile components, and other applications requiring high strength at extremes of temperature.
René 41 was used to create the outer shell of the Mercury capsule due to its ability to retain high strength at very high temperatures.[1]
The composition is: chromium 18-20%, cobalt 12%, molybdenum 9-10.5%, titanium 3.0-3.3%, aluminium 1.4-1.6% with the balance nickel.