Forty Years since the Invention of SUPRAL Alloys and Look where we Are now

Abstract

Prior to 1969 the pioneering work carried out by Backofen and Fields in the USA and Johnson and Hundy in the UK demonstrated the 'promise' of Superplastic Forming. Using fine grained dual phase alloys, typically of eutectic or eutectoid compositions, they produced some of the very first superplastically formed prototype components. Although not always 'practical', these dual phase alloys were stable when heated and if appropriately processed often proved to be very superplastic. At that time 'dilute' alloys, including the majority of commercial aluminum alloys, having only a small volume fraction of alloying additions, were thought not to be capable of superplastic behavior due to their propensity to grain coarsen when heated. Breakthrough came in 1969 when at the research labs of Tube Investments, Hinxton Hall Nr Cambridge UK; the first 'SUPRAL' type dilute superplastic aluminum alloys were created. This paper describes the events and 'science' that led up to this development and the remarkable technology that has emerged since the authors began their superplasticity careers more than forty years ago. The future direction that this intriguing technology is likely to take is also explored.