KNOOP-HARDNESS STUDIES ON PHENANTHRENE SINGLE-CRYSTALS

The Knoop microhardness studies have been carried out on phenanthrene single crystals. The variation of hardness with load has been explaine d in terms of the ease of slip and compared with that of the Vicker's hardness behaviour. The plot shows three peaks of which the first two peaks at 3.75 and 7.5 gm loads are,very close to each other and are ha ving hardness values 9.24 and 8.48 kg/mm(2) respectively. The third pe ak is at load 11.25 gm and has a hardness value of 8.45 kg/mm(2). The first two peaks correspond to the first peak at 42.5 gm load observed with pyramidal hardness studies having a hardness value 7.1 kg/mm(2). The peak was due to the slip on the (20(1) over bar) plane in the [010 ] direction. The present observation suggests that the (20(1) over bar )[010] dislocations split into partials.