Effect of lithium on the structural-phase state of rapidly solidified Al–Mg–Li alloy during heat treatment

Abstract

The effect of lithium on the structural-phase state of aerospace aluminum alloy 1421 of the Al–Mg–Li system prepared by rapid solidification is studied. Analysis of the composition of the surface layers of alloy samples carried out by means of nuclear reaction analysis establishes that lithium diffuses to the surface at elevated treatment temperatures and its concentration in a thin surface layer (0.1 μm) reaches 38 at %, which is 4.8 times higher than the calculated Li content in the alloy. By measuring the microhardness, strengthening of the samples is determined upon isothermal annealing at a temperature of 400°C, which is caused by the precipitation of metastable lithium-containing phases. The results of X-ray diffraction analysis indicate an increase in the fraction of Li2O2 peroxide on the foil surface upon annealing.