Features of the microstructure and low-temperature yield stress of quenched Al-Li alloys

The features of the microstructure of quenched Al-Li alloys with lithium co ncentration below the solubility limit (3.8 at. %) and above the solubility limit (7.0 and 10.4 at. %) are studied by the x-ray diffractometry. In add ition to the standard structural reflections, the diffraction patterns of a ll the alloys show diffuse halos that fall off in intensity as the lithium concentration is increased. As a result of an analysis of the intensity of the diffuse scattering of x rays it is established that the observed halos are due to short-range order of the layered type in regions with a characte ristic radius of 1.5 nm. The decrease in the intensity of the diffuse halo on the diffraction pattern of the alloy Al-10.4 at. %Li and the appearance of new structural reflections are explained by the precipitation of dispers e particles of the delta' phase. It is shown that these particles have a su bstantial influence on the mechanism of plastic deformation in these alloys in the temperature region 40-170 K. (C) 2000 American Institute of Physics . [S1063-777X(00)01507-3].