Lattice strain distributions due to elastic distortions and GND development in polycrystals

Techniques for the determination of lattice spacing distributions resulting from elastic distortion and from the development of a Burger's discontinuity (or equivalently, geometrically necessary dislocation density), are presented within a computational crystal plasticity framework, and a number of validatory analyses discussed. The contributions from both elastic distortions and Burger's circuit discontinuity to lattice spacing distributions and corresponding peak widths are evaluated and assessed for an fcc single crystal bearing elastic distortion and a plastic strain gradient. The single crystal analyses show that the elastic distortions lead to peak broadening and that at the initiation of plastic slip in the presence of a plastic strain gradient, the Burger's discontinuity (or equivalently GND density) also contributes to the peak broadening and may dominate as the strains become larger. After slip initiation, the contribution from elastic distortion remains largely unchanged. Analyses of random and textured polycrystals under uniaxial (100) straining to 5% show that the Burger's discontinuity contribution to peak broadening tends to dominate earlier over that from elastic distortion relative to the single crystal behaviour, because of the higher level of heterogeneity present. The randomly textured polycrystal showed more {100} peak broadening than that for the textured sample as a result of the relatively higher heterogeneity in the former.