4^th International Aluminium Lithium Conference

J. Phys. Colloques 48 (1987) C3-11-C3-24
DOI: 10.1051/jphyscol:1987302

PROGRESS TO ALUMINIUM-LITHIUM SEMI-FABRICATED PRODUCTS

R. GRIMES¹, T. DAVIS², H.J. SAXTY³ et J.E. FEARON<sup>4

1</sup>  British Alcan Aluminium plc, c/o Alcan International Limited, Southam Road, Banbury , GB-Oxon OX16 7SP, Great-Britain
²  Alcan Plate Limited, P.O. Box 383, Kitts Green, GB-Birmingham B33 9QR, Great-Britain
³  British Alcan Sheet Limited, David's Loan, GB-Falkirk FK2 7XT, Scotland, Great-Britain
⁴  Alcan High Duty Extrusions Limited, Lillyhall, GB-Workington CA14 4JY, Cumbria, Great-Britain

Abstract
British Alcan Aluminium plc installed a small scale melting and casting facility for aluminium-lithium based alloys at the Alcan Plate factory, Birmingham, England that was completed in early 1985. Since May 1985 the Lital alloys have been in regular production in the form of sheet, plate, extrusion, tube and forging stock. During the two years of production, attention has been paid to optimisation of all aspects of the manufacture of the semi-fabricated products and considerable improvements in properties have been achieved. This paper outlines the progress and compares current typical properties with guaranteed minima and the properties of the established aerospace alloys. Good damage tolerant properties have been achieved with Lital C (8090) in a lightly aged condition. In sheet form toughness is slightly better than that of 2024 T3 at the same strength level and the corrosion/stress corrosion behaviour of the Lital alloy is superior to that of 2024. In plate and extruded forms strength properties match those for 2024 while toughness in the rolling plane is superior. Though thickness toughness matches that of 2024 while fatigue crack growth rate is less than for 2024. In the medium strength Lital A (8090) condition considerably improved strengths and strength/toughness relationships have been achieved by optimisation of stretching and final ageing practices. Strengths attainable are close to the targets originally set for the high strength Lital B (8091). Plate up to 100 mm thick has been produced exhibiting good ductility and fracture toughness in the short transverse direction. In sheet form the medium strength alloy is unrecrystallised and, therefore, exhibits some anisotropy of properties but strength targets are being achieved. Demand for the 8090 alloy has reduced the development time available for the high strength Lital B (8091) alloy. So far only limited production of Lital B has occurred at Kitts Green but very good strength properties have been achieved. Using optimised stretching and ageing practices, it appears that very high strength levels can be achieved in thin 8091 plate, although this is by sacrifice of the through thickness properties.