U. Ramamurty et al., EFFECT OF HEAT-TREATMENT ENVIRONMENT ON LI DEPLETION AND ON MECHANICAL-PROPERTIES IN AL-LI ALLOY SHEETS, Journal of Materials Science, 28(23), 1993, pp. 6340-6346
The loss of lithium during solution heat treatment of various commerci
al Al-Li alloy sheets as a function of the heat treatment environment
is investigated. The thickness of the soft layer formed due to solutio
nizing at 530-degrees-C for 30 min in laboratory air, argon and salt b
ath environments is determined by microhardness measurements. Li loss
from the surfaces is interpreted with the help of normalized microhard
ness profiles. Results showed that prior Li-depleted layer does not hi
nder further loss of Li from the surfaces and the heat treatment envir
onment has relatively little effect on the loss of Li. The loss of ten
sile strength due to the Li depletion in the peak-aged condition is fo
und to be more pronounced in 1 mm thick sheet than in 1.5 mm or 2 mm t
hick sheets. Possible reasons for loss of strength in 8090 series allo
ys after the heat treatment are discussed. Explanations for the observ
ed ductile fracture features in Li-depleted layers is offered,