Fig. 5: Dislocation mobility effects on the anomalous hardness of tantalum carbides.
From: Insights into the anomalous hardness of the tantalum carbides from dislocation mobility
a Comparison of nanoindentation hardness measurements for bulk (circle markers) and thin-film (square markers) TaCx at different x. Each datum represents the mean value for 50 indentation tests on a single sample, with included error bars indicating the standard error for each sample. b TEM image of indented bulk TaC0.75 sample, showing significant cracking, and with slip on {110}B1 and {111}B1 planes evident from the angular separation of dislocations on intersecting planes (dashed guide lines offset from the dislocations so as not to obscure the dislocations). c TEM image of indented bulk TaC, showing abundant evidence of intersecting dislocations on the close-packed {111}B1 planes. d SEM image of a nano-indent in a coarse-grained bulk TaC sample, showing signs of pile-up. e SEM image of a nano-indent in a nanocrystalline TaC thin film, showing cracking along indenter edges and no pile-up. f Atomic force microscopy measurements of the surfaces of indented bulk and thin-film TaC samples, confirming the lack of significant pile-up in the nanocrystalline film.
