An X-ray Fourier line shape analysis in cold-worked hexagonal metals

Abstract

Detailed Fourier analysis of line shapes using the technique of Warren, has been performed on cold-worked hexagonal magnesium, zinc and titanium and a partially recovered state of titanium at room temperature. X-ray diffraction profiles from fault-unaffected 10.0, 00.2, 11.0, 20.0, 11.2, 00.4 and fault-affected 10.1, 10.2, 10.3, 20.1 and 20.2 reflections have been recorded in a Geiger counter diffractometer with copper radiation and the microstructural parameters have been evaluated. A small anisotropy in both domain sizes and root mean square strains has been observed for these materials; this is similar to the study on zirconium in Part 1. The average values of these are, respectively, of the order of 380 A and 1.58×10−3 for titanium in the cold-worked state with a small recovery on annealing, 1650 A and 0.71×10−3 for magnesium, and 1060 A and 0.57×10−3 for zinc. Least-squares analysis applied to fault-affected reflections has yielded very small concentrations of deformation faults, α (≃ 8.0×10−3), and growth faults, β (≃ 2.0×10−3), in the cold-worked state of titanium similar to those in zirconium, and negligible concentrations of these (α ≃ 0.63×10−3, β ≃ 0.21×10−3) in magnesium. The presence of deformation and growth faults could not be detected in zinc, possibly due to considerable recovery. An estimate of stacking-fault energy, γ, has also been made in titanium and magnesium from an expression taking basal slip and the value of α into account, and this has been found to be quite low for both materials. The favourable slip mode in these hexagonal metals has been discussed in the light of the experimental results.