Mechanical properties of single crystals of transition metals diborides TMB2 (TM = Sc, Hf, Zr, Ti). Experiment and theory

Resumo

The mechanical behaviour of TMB₂ whiskers (TMB₂ = Sc, Hf, Zr, Ti) of 10–20 μm in diameter of the directionally reinforced ceramics LaB₆–TMB₂ was experimentally studied by the nanoindentation. The pop-in (the abrupt elastic–plastic transition in the indenter penetration) caused by the nucleation of dislocations in the previously dislocations-free region under the imprint was observed in all samples under study. For the first time the experimental estimations of the theoretical shear strength of these materials are obtained. Zone structures and types of interatomic bonds for TMB₂ (TM= Sc, Zr, Hf, Ti) are theoretically calculated. The effects of the electronic structures on mechanical properties of diborides of transition metals were analyzed.