The influence of stress states on the martensitic transformation in Y-TZP ceramic

Abstract

Abstract It has been studied the influence of the type of stress state arising during different types of loading - for axial compression, diametral compression (Brazilian test) and three-point bending of Y-TZP ceramics with different grain sizes. It was shown that with increasing grain size of ceramics there is an increase in strength properties. The maximum values of all strength characteristics are fixed for ceramics with a grain size of 1.55 microns. It was found that on the fracture surfaces the formation of a monoclinic phase caused by the tetragonal–monoclinic transformation under the influence of applied stresses after axial compression test, Brazilian test and three-point bending test. As the average grain size increases, the content of the monoclinic phase increases after all types of mechanical tests. For ceramics with the average grain size of 0.53 µm, regardless of the type of loading, the content of the monoclinic phase on the fracture surface was approximately 5-7%. For ceramics with a maximum grain size of 1.55 microns after axial and diametrical compression tests, the content of the transformation phase increased to 27 % and after bending tests up to 39 %. The increased content of the monoclinic phase on the fracture surface after bending tests, in comparison with the axial and diametrical compression tests, is due to a complex stress-strain state, when during deformation areas with tensile and compressive stresses are formed on the fracture surface.