Microstructure and texture formation in extruded lead sulfide (galena)

Lead sulfide (galena) of different purity and grain size was extruded through a round and rectangular die at temperatures between 773 and 923 K. Global and local lattice preferred orientations (here referred to as textures) were measured by neutron and electron back-scattering diffraction. Tension leads to a <100> <111> double fibre texture. Pure shear deformation yields texture components near the ideal face-centered cubic metal brass, copper, Goss and cube positions. The intensity of the components depends on the purity and/or grain size. The microstructure is partially recrystallized. Electron back-scattering diffraction indicates that in tension the <100> and in pure shear the Goss and cube components are associated with dynamic recrystallization. The deformation texture can be qualitatively explained by the full and relaxed constraints Taylor model using slip on {100}<110>, {110}<110> and {111}<110> systems. The texture formation in lead sulfide compares well with that observed for other ionic crystals with the NaCl-structure as well as for face-centered cubic metals with a high stacking fault energy.