Development of an aluminum alloy for elevated temperature applications

Non-ferrous light alloys including aluminum and magnesium have maximum effective operating temperatures of about 200°C which is equal to their aging temperatures. While this temperature capability is adequate for most traditional applications, demands from important industrial sectors as well as the military require lightweight alloys that can operate in temperature ranges of 250-300°C. For example, the need to reduce the exhaust emissions of medium and heavy-duty diesel engines has led to the use of two-stage series turbocharger designs for the air system. Single stage compressors run at an outlet air temperature of approximately 175°C at sea level. This is the approximate temperature limit for the currently used cast 354-T61 aluminum alloy impellers. Second stage outlet air temperatures are predicted to reach 260°C or higher at sea level conditions and this temperature will increase with operating altitude. Efforts were made to develop an Al-Cu alloy with scandium addition which is able to retain its strength at 250°C. Details of the alloy development along with results are presented and discussed in this publication.