In September we decided that KoBo extrusion / deformation experiments with high purity Zinc need to be repeated. Some of the previous samples have been analyzed after significant amount of time from original extrusion process. Some others were analyzed after much shorter time. Discrepancies in mean grain sizes observed in those two cases (much smaller grain in 'younger' sample), points to possibility of some recrystallization processes that might occur even in room temperature.
Therefore new samples of zinc after KoBo from now on are kept in liquid nitrogen in order to prevent uncontrolled recrystallization. New samples similarly to the old ones have been extruded from 40 mm diameter ingot to 1,8 mm wire in room temperature. During extrusion process, wire have been cooled with water, and immediately after extrusion samples have been cut and placed in dewar with liquid nitrogen.