Regularities of MgO single-crystal failure in microindentation

Microhardness and structural defects of GaSe layered semiconductor

“…3 GPa and E [1 0 0] ¼36.6 GPa [3], which correlates with anisotropy of microhardness. Recovery of the indentation is in inverse proportion to the Young's modulus [10]. This explains some asymmetry of the indentation shape (Fig.…”

“…4 shows dependences of microhardness on time under load for three discrete loads: 0.2, 0.3, and 0.5 N. It is seen that the highest hardness appears in the case of the lowest load and the shortest time under load. This is caused by the fact that lifting of the load is accompanied by elastic recovery of the indentation and relaxation of stresses [10]. In the case of a small load when elastic strain is the main part of the deformation, the percentage of the indentation recovery after the uplifting of the indenter is greater than that in the case of a higher load when plastic strain is significant.…”

“…The measurements have shown that at the load P¼0.3 N microhardness are H [1 1 0] ¼350 MPa and H [1 0 0] ¼250 MPa. Thus, there is the 1st order anisotropy [10] of microhardness, which reflects a difference in microhardness in different directions in one plane. The coefficient of anisotropy of microhardness is k¼H max /H min ¼1.4.…”

“…The coefficient of anisotropy of microhardness is k¼H max /H min ¼1.4. Anisotropy of microhardness is caused by anisotropy of chemical bonds [10]. In the (0 0 0 1) plane of GaSe crystals there is anisotropy of Young's modulus, E [1 1 0] ¼ 92.…”

Influence of impurity type on microhardness anisotropy of NaCl single crystals

“…The microhardness anisotropy of I and I1 kinds (the dependence of hardness on the direction for one face and the dependence of hardness on the type of face) for alkali halide crystals such as NaCl has been studied (AERTS et al; BERKOVICH; BROOKES et al 1971; BOYARSKAYA; BOYARSKAYA et al 1978, 1979BROOKES et al 1975; NA-RASHIMA REDDY ; HARI BABU; BOYARSKAYA et al 1986), the influence of temperature (BOYARSKAYA; BOYARSKAYA et al 1978, 1986BROOKES et al 1975;BOYARSKAYA et al 1986) and radiation defects (BOYARSKAYA; BOYARSKAYA et al 1978) on this characteristic has been investigated. An interesting phenomenon was revealed by using the Knoop indentor -the change of the microhardness anisotropy sign in dependence on the temperature, indentation time and the microhardness change in the series of crystals, having the same lattice structure (BOYARSKAYA et al 1978, 1979BOYARSKAYA et al 1979;BROOKES et al 1975;ROYARSKAYA et al 1986).…”