Abstract
Abstract. The anisotropy of the mechanical properties of single crystal ZrO2 — 2.8 mol.% Y2O3 solid solutions has been studied. The crystals have been grown by skull melting technique. The microhardness and fracture toughness have been tested for different crystallographic planes by indentation with different indenter diagonal orientations. The study shows that the microhardness of the material depends on the crystallographic orientation but slightly whereas the fracture toughness varies for different planes. The maximum fracture toughness has been observed in the crystal specimen cut laterally to the orientation. We have studied the anisotropy of the microhardness in the material for different indenter diagonal orientations. The maximum fracture toughness has been obtained for the {100} plane and the indenter diagonal orientation. The phase composition inside and outside the indents on the {100}, {110} and {111} surfaces for 20, 3 and 1 N loads has been studied in local areas using Raman spectroscopy. The degree of the tetragonal−monoclinic transition has been evaluated for different crystallographic planes and different indenter diagonal orientations. The tetragonal−monoclinic transition proves to be anisotropic, and this affects the transformation hardening mechanism. The maximum amount of the monoclinic phase is present in the vicinity of the indent in the {100} plane for the indenter diagonal orientation. The highest fraction toughness has also been observed in the {100} plane for the indenter diagonal orientation. Probably, the abovementioned indenter diagonal orientation provides for the maximum stress concentration along the coherent conjugation planes between the tetragonal and the monoclinic phases during the tetragonal−monoclinic transition, i.e. (100)t||(100)m and [001]t||[010]m.
Highlights
Полученные на пластинах, вырезанных из кристаллов ZrO2 — 2,8 % Y2O3 перпендикулярно к разным кристаллографическим направлениям [Microhardness and fracture toughness of plates cut from ZrO2 — 2.8 mol.% Y2O3 crystals laterally to different crystallographic orientations]
The microhardness and fracture toughness have been tested for different crystallographic planes by indentation with different indenter diagonal orientations
The study shows that the microhardness of the material depends on the crystallographic orientation but slightly whereas the fracture toughness varies for different planes
Summary
Кристаллы частично стабилизированного диоксида циркония ZrO2 обладают высокими механическими и трибологическими характеристиками [1,2,3]. Исследование механических свойств методом индентирования с использованием пирамиды Виккерса в кристаллах ZrO2, стабилизированных 3 % (мол.) Y2O3, показало [17], что доминирующими процессами механизма деформации в области температур ниже температуры тетрагонально−моноклинного фазового перехода являются сегнетоэластичное превращение и мартенситная трансформация, хотя имеет место и сдвиговая деформация. В работах [18,19,20] показано, что кристаллы твердых растворов на основе ZrO2 при содержании стабилизирующего оксида иттрия от 2,5 до 5 % (мол.) Y2O3 представляют смесь тетрагональных фаз: трансформируемой (t) и нетрансформируемой (t′). Цель работы — исследование анизотропии механических свойств кристаллов ZrO2 — 2,8 % (мол.) Y2O3 методом индентирования, установление корреляции между химическим составом, структурой, кристаллографической ориентацией тетрагональных кристаллов на основе диоксида циркония и их механическими свойствами, а также определение действующего механизма упрочнения
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