Observations on Growth Shape, Plastic Deformation and Slip Line of Sodium Chloride Whisker

概要

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Some observations have been made on sodium chloride whiskers grown by the cellophane method following Amelinckx. Three different growth shapes (needle, platelet and pyramid) were seen to grow on the cellophane surface. The crystal grew entirely at the base tip growth or lateral thickening did not take place at all. The whisker exhibited large plastic deformation (〓l/l_o=50%-90%) before fracture occurred. The critical strain (plastic elongation at fracture) increased with decreasing cross-sectional area, but it decreased rapidly to zero when the cross-sectional area decreased less than 1×10^<-3>mm^2. The tensile strength, on the contrary, increased strongly with the decrease in cross-sectional area below 1×10^<-3>mm^2. Plastic deformation produced slip lines on the crystal surface. They were observed by optical microscope and by electron microscope. The slip usually occurred on single set of (110) slip plane systems in relatively large region of a whisker. In some cases, the transverse (90-degree) slip lines were wavy, and branching of the slip line was seen. But in other cases, they were straight and parallel. The 45-degree slip lines could not be observed by electron microscope. Cross slips were rarely observed. Etch pit observations revealed that the whisker contained many dislocations. Some interpretations for the results were attempted to give.
東北大学の論文