Plastic deformation of CoO single crystals

Abstract

Résumé. 2014 Des essais de compression à vitesse constante (03B5 ~ 6 x 10-5 s-1) ont

Deformation of MgO by Vickers microindentation tests

“…The relation between hardness and deformation by dislocation glide is not straightforward. The strength of NiO is between that of MgO and CoO (Table 1) [9]. Irregular cracking occurs around indentations in NiO with no deformation of the indentation (Fig.…”

“…5) There is no cracking around indentations in CoO (Fig. 5) which is the softest crystal under hardness testing (Table I) and the hardest under conventional uniaxial testing [9]. The relation between hardness and deformation by dislocation glide is not straightforward.…”

Plastic deformation down to 4.2 K of CoO single crystals and T.E.M. observation of dislocations

“…Dominguez-Rodriguez, J. Castaing (*), H. Koisumi (1), and T. Suzuki (1) Departamento de Optica e Instituto Ciencias Materiales Sevilla (C.S.I.C.) Facultad [4] and [5]. Specimens were cut as parallelopipeds (2.5 x 2.5 x 6 mm3) with {100} faces and compressed along their longest dimension.…”

“…The specimens were furnace cooled at 20 Klmn. They entered the Co304 phase field at about 550 °C, at least 300 °C lower than for annealing in air [4]. Optical and TEM observations did not reveal any Co304 precipitates, contrary to the case of air-quenched crystals [5].…”

“…In order to control the thermodynamic parameters, crystals were annealed in air at 1200 °C ; they contained a regular array of Co304 precipitates [5] ; they were very strong as long as tests were performed in the range of stability of Co304 [4]. However, this hardening cannot be explained on the basis of dislocation precipitate interactions ; the Orowan stress is of the order of 2 MPa, much less than the flow stress [4,5] (Fig.…”