Evolution of texture, microstructure and mechanical property anisotropy inan Al-Li-Cu alloy

The evolution of hot deformation texture, microstructure and yield strength anisotropy in an Al-Li-Cu alloy AF/C489 was studied in the as-extruded, so lution heat treated and peak-aged condition. Cast AF/C489 alloy with a rand om texture was extruded at six temperatures ranging from 260 to 538 degrees C and immediately quenched to capture texture and microstructure at the ex trusion temperature. In the as-extruded condition, significant amounts of t he major rolling texture components, namely, Br {112}[110], S {123}[634] an d Cu {112}[111] were observed at all extrusion temperatures. However, at ex trusion temperatures above 480 degrees C there was a sharp rise in the inte nsity of Br component. When the extruded alloy was solution treated the Br intensity remained stable for the two highest extrusion temperatures. Howev er, solution heat treatment (SHT) following extrusion at lower temperatures resulted in the loss of all the rolling texture components including Br. F urthermore, the solution heat treatment following extrusion at temperatures below 330 degrees C showed presence of significant amount of ND rotated cu be ({100}[130]). It is suggested that formation of Br texture may be due to the development of shear bands. Increase in dynamic recovery at high extru sion temperature enhances the shear banding tendency and consequently incre ased presence of Br. This is consistent with negligible recrystallization d uring solution treatment following elevated temperature extrusion as observ ed by optical microscopy. Significant recrystallization during SHT followin g low temperature extrusion results in the presence of rotated cube compone nts. This is consistent with the presence of more particles at low temperat ure as observed by transmission electron microscopy. The yield stress aniso tropy in the SHT material is attributed to crystallographic texture in the SHT material whereas in the extruded case the anisotropy is due to the comb ined effect of particles and texture. (C) 1998 Elsevier Science S.A. All ri ghts reserved.