Evolution of microstructures and mechanical properties in coarse- and fine-grained Zn during drawing deformation at room temperature

Pure Zn with different grain sizes obtained via extrusion at different temperatures was drawn in multiple passes at room temperature. The evolution of the microstructures and mechanical properties during drawing was examined using scanning electron microscopy and room-temperature tensile tests. The results indicated that pure Zn with a grain size of 80 μm broke frequently when the drawing deformation reached 4 % and could not be drawn further. A high density of parallel or intersected $\left\{10\bar{1}2\right\}$ compression twins was generated after drawing, leading to a drawing direction (DD)//<0001> deformation texture and work-hardening phenomenon. When the grain size was reduced to 15 μm, pure Zn could be drawn continuously at room temperature without breaking, exhibiting unusual work softening. In particular, when the cumulative deformation was 4 %, the grain size of Zn increased to >10 times the initial size and decreased to approximately 70 μm with further drawing. With increasing deformation, the grains gradually rotated, and the non-basal texture gradually changed completely, which was conducive to continuous deformation. The fracture elongation of Zn reached 140 % owing to the initiation of the intergranular deformation mechanism and non-basal texture; however, the tensile strength decreased from 130 MPa to 90–110 MPa after drawing.