New Al-Mg-Li-C dispersion strengthened alloy - Part 2 - Optimisation of material for forging applications

This paper describes work aimed at optimising the forging process and mecha nical properties of a new powder route Al - Mg - Li - C dispersion strength ened alloy, specifically for forging applications. The alloy, of the AA 509 1 type, has a nominal composition of Al - 1.2Li - 5Mg - 0.35C (wt-%), and i s non-heat treatable. Materials were supplied by AMC Ltd, and evaluated in laboratory based forging trials to determine the influence of forging param eters on mechanical properties, including an investigation of using extrude d bar as forging stock. The process was scaled up to produce an industrial forging, using an EH101 helicopter part, which was cut up for detailed mech anical property assessment. It was found that adequate hot working of the m aterial is needed for good toughness, and that the balance of strength to t oughness can be controlled by the forging temperature. The new alloy, in th e as forged condition, meets the minimum tensile and fracture toughness lev els set in the draft AECMA Specification for AA 5091 forgings. MST/4754.