4^th International Aluminium Lithium Conference

J. Phys. Colloques 48 (1987) C3-341-C3-346
DOI: 10.1051/jphyscol:1987339

EFFECT OF DISPERSOID-FORMING ADDITIONS ON THE RESPONSE TO HEAT TREATMENT OF SPLAT-QUENCHED Al-Li-X ALLOYS

R.C.A. PRATT¹, P. TSAKIROPOULOS², H. JONES³, R.W. GARDINER⁴ et J.E. RESTALL<sup>5

1</sup>  Osprey Metals Ltd, GE-Neath, SA11 1NJ, West Glamorgan (GB).
²  Department of Materials Science and Engineering, University of Surrey, GB-Guildford, GU2 5XH, Surrey (GB).
³  University of Sheffield, Department of Metallurgy, GB-Sheffield, S1 3Jd, Great-Britain
⁴  Materials and Structures Division, Royal Aircraft Establishment, GB-Farnborough-Hants, GU14 6TD, Great-Britain
⁵  Propulsion Department, Royal Aircraft Establishment, Pyestock, GB-Farnborough-Hants, GU14 OLS, Great-Britain

Abstract
The paper reports some results of a research programme which is directed towards identifying dispersoid-forming additions, made possible via rapid solidification , that are more effective than the 0.05 to 0.25wt%Zr addition currently made to first-generation wrought-ingot aluminium alloys containing lithium. In the study ~ 2' vol % of transition metal aluminides were dispersed in an Al-Li alloy matrix using the two-piston splat-quenching technique. The approach adopted for initial selectivity was to ascertain the stability and related effects of the aluminide dispersoids at the (Al-Li) solution temperature of 540°C for treatments between 1 and 1000 h. Hardness as-splatted increased notably as a result of the dispersoid forming addition and increased further in 1h at 540°C, decreases after more prolonged treatment at 540°C being attributable partly to loss of lithium and partly to microstructural coarsening. Selected candidate alloy systems-were subjected to ageing heat treatments at 160°C with or without prior solution treatment at 540° for 1 h. Increases in microhardness, typically by 40 kg/mm² higher than for the corresponding binary Al-Li alloy, were obtained at each stage of ageing. Al-4.1wt% - 0.5wt%Mo demonstrated outstanding behaviour, both in stability at 540°C and in response to ageing treatment at 160°.