B. Ya. Farber

Mechanisms of energy dissipation during displacement- sensitive indentation in Ge single crystals at elevated temperatures

Abstract Load-displacement indentation tests have been performed in Ge single crystals on a newly designed displacement-sensitive hardness tester in the temperature range 20–450°C. The deformation substructure in the vicinity of the indentation impressions was investigated using selective etching. The energy dissipated during the loading-unloading indentation cycle has been measured and compared with the extent and the structure of the deformation zone. Mechanisms of plastic flow and fracture during indentation are discussed.

Energy Dissipation during High Temperature Displacement‐Sensitive Indentation in Cubic Zirconia Single Crystals

A newly designed displacement-sensitive hardness tester capable of performing load-displacement experiments in the temperature range 20 to 800 °C is described. Load-displacement indentation tests have been performed in 9.4 and 21 mol% Y 2 O 3 fully stabilized cubic ZrO2 single crystals. The effect of the alloying concentration on the deformation substructure in the vicinity of the indentation impressions was investigated using selective etching. The energy dissipated during the loading-unloading indentation cycle has been measured and compared with the extent and structure of the deformation zone. The relative roles of the different energy dissipation mechanisms during indentation are discussed.

A dislocation mechanism of crack nucleation in cubic zirconia single crystals

Abstract The dislocation structure around elevated-temperature indentations on {111} planes of 9·4 and 21 mol.% Y2O3 fully stabilized cubic ZrO2, was investigated using selective etching and transmission electron microscopy (TEM). The temperature dependences of the microhardness and the extent of the plastic zone were measured. Different fracture modes were detected in the two materials. Cracking arising from interaction between slip bands was observed in the 21 mol.% Y2O3 material and direct evidence of the formation of Lomer-type dislocation pile-ups leading to crack nucleation was obtained by TEM. The mechanisms of dislocation plasticity and fracture during indentation of cubic zirconia are discussed.

Dislocation velocities in cubic zirconia (ZrO2) single crystals

Abstract Dislocation velocities between 1100 and 1450°C in 9·4mol.%Y2O3 fully stabilized cubic ZrO2 single crystals were studied using the stress pulse-etch-pit technique. The stress and temperature dependences of the edge and screw dislocation velocities were measured at engineering stresses from 60 to 185 MPa. The activation energy for motion of the edge dislocations (5·0 ± 0·0·4 eV) is slightly lower than that for screw dislocations (5·6±0·6eV). At the lower end of the temperature range, the stress exponent m of the edge dislocation velocities is close to unity but increases modestly (to about 3·6) with increasing temperature. With reasonable choice of parameters, the data can be attributed to a Peierls potential, to jog dragging or to solute pinning.