Texture / Yield Strength Correlations in Al-Li Near-Net-Shape Extrusions

Abstract

The objective of this investigation was to correlate textural characteristics with yield strength anisotropy in identical T-stiffened extruded panels manufactured from the Al-Li alloys 2195, RX818 and 2096. Two regions within the panels were examined; mid-way between the stiffeners (skin) and directly beneath the stiffeners (base). In all three extrusions, the texture in the skin region was comparable to rolled product and that in the base region similar to axisymmetric extruded product. The results indicate that the yield strength anisotropy tended to be greater in the base than in the skin, regardless of alloy. Two variants of the Taylor model for mechanical anisotropy in f.c.c. materials were employed to study the relationship between texture and yield strength anisotropy. The first variant assumed that all grains exhibit axisymmetric strain, whereas the second variant assumed that individual grains adopt the strain state which results in the minimum yield strength for each grain. Correlation of the results showed that the second variant consistently worked better than the first variant and also provided a better correlation for the skin regions than the base regions. Discrepancies between the model predictions and the measured yield strength anisotropy are discussed in terms of the microstructural and textural variations observed.