Texture gradient,average texture,and plastic anisotropy in various AI–Li sheet alloys

The variation of texture through the thickness and the average texture of sheet material of recrystallised AA 8090 and unrecrystallised AA 8090 (crossrolled) and AA 2090 AI–Li alloys have been investigated. Conventional (lithium free) AA 2024 alloy in the annealed condition was used as a reference material. The quantitative orientation distribution functions were determined via X -ray diffraction and neutron diffraction techniques. Using X -ray diffraction, textures of layers at various distances from the surface to the centre of the sheets were examined to achieve the texture gradients. The average textures were determined either via neutron diffraction using cylindrical stacked specimens or by summing the texture results obtained via the X-ray techniquefor the various layers. It is shown that the intensity of the common rolling textures, i.e. {112} <111>, {123} <634>, {110} <112>, and shear texture {100} <011> markedly varied through the thickness of unrecrystallised AA 8090 and AA 2090 AI–Li sheets. Also, in recrystallised AA 8090 AI–Li and AA 2024, a variation of the recrystallisation texture components {001} <100> and {011} <100> through the thickness was found. The quantitative texture data in conjunction with Taylor theory were used to predict the plastic anisotropy in terms of the plastic strain ratio as afunction of the angle a between the rolling and tensile directions. This prediction shows that the effects of texture can explain well the anisotropy in recrystallised AI–Li material (AA 8090). For unrecrystallised materials (AA 8090, AA 2090), a correct trend in plastic anisotropy is predicted; however, the calculated values in the 45° direction are larger than those determined experimentally.

MST/1910