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Investigation of Indentation Fracture Toughness (KIC) and Weibull Parameters of 0.25Li2O.2SiO2-0.75BaO.2SiO2 Glass-Ceramic

Ertuğ B., Çetiner B. R., Gökçe H., Erkmen Z. E., Öveçoğlu M. L.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

1963--1968

EN

In the present study, mechanical properties of 0.25Li2O.2SiO2-0.75BaO.2SiO2 glass-ceramic were investigated. The trans-formations‘ temperatures were determined by DTA instrument. The optimum nucleation temperature was found to be 540°C. This suggested the crystallization temperatures as 675, 720 and 800°C. After carrying out crystallization heat treatments, Vickers indentation test was applied. In order to determine the indentation fracture toughness (KIC), crack half-length ‚c‘ of the samples was measured. To calculate KIC, Young’s modulus, E and the measured hardness, Hv were used. Using KIC and probability of fracture ‚P‘, ln ln[1/(1 − P)] – ln KIC graph was drawn based on the Weibull distribution equation. Consequently, Weibull modulus, ‚m‘ and scale parameter, ‚K0‘ were determined and compared with each other.

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Fracture toughness of advanced alumina ceramics and alumina matrix composites used for cutting tool edges

Szutkowska M.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 54, nr 2

202--210

EN

Purpose: Specific characteristics in fracture toughness measurements of advanced alumina ceramics and alumina matrix composites with particular reference to α-Al2O3, Al2O3-ZrO2, A2O3-ZrO2-TiC and AI2O3-Ti(C,N) has been presented. Design/methodology/approach: The present study reports fracture toughness obtained by means of the conventional method and direct measurements of the Vickers crack length (DCM method) of selected tool ceramics based on alumina: pure alumina, alumina-zirconia composite with unstabilized and stabilized zirconia, alumina-zirconia composite with addition of TiC and alumina-nitride-carbide titanium composite with 2wt% of zirconia. Specimens were prepared from submicro-scale trade powders. Vicker’s hardness (HV1), fracture toughness (KIC) at room temperature, the indentation fracture toughness, Young’s modulus and apparent density were also evaluated. The microstructure was observed by means of scanning electron microscopy (SEM). Findings: The lowest value of KIC is revealed by pure alumina ceramics. The addition of (10 wt%) unstabilized zirconia to alumina or a small amount (5 wt%) of TiC to alumina-zirconia composite improve fracture toughness of these ceramics in comparison to alumina ceramics. Alumina ceramics and alumina-zirconia ceramics reveal the pronounced character of R-curve because of an increasing dependence on crack growth resistance with crack extension as opposed to the titanium carbide-nitride reinforced composite based on alumina. R-curve has not been observed for this composite. Practical implications: The results show the method of fracture toughness improvement of alumina tool ceramics. Originality/value: Taking into account the values of fracture toughness a rational use of existing ceramic tools should be expected.

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Selected mechanical properties and microstructure of Al2O3ZrO2nano ceramic composites

Szutkowska M., Smuk B., Kalinka A., Czechowski K., Bućko M., Boniecki M.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 48, nr 1

58--63

EN

Purpose: Basic mechanical properties of the studied tool materials and microstructure of alumina-zirconia ceramic composites with fraction of nanopowders have been presented. Design/methodology/approach: The present study reports selected properties obtained by reinforcing Al2O3 with 15 wt% ZrO2 (partially stabilized with Y2O3-Y5) and, non-stabilized zirconia. Specimens were prepared based on submicro- and nano-scale trade powders. Vickers hardness (HV1), wear resistance and fracture toughness (KIC) at room and elevated temperatures characteristic for tool work were evaluated. Microstructure was observed by means of a scanning electron microscopy (SEM). Preliminary industrial cutting tests in the turning of higher-quality carbon steel C45 grade were carried out. Findings: The addition of nanopowders does not result in a significant improvement in fracture toughness at room temperature. A reduction in fracture toughness of KIC(ET) by approximately 20% is observed at elevated temperature (1073 K) for the specimen only with submicro powders in comparison to that at room temperature. Addition of the powder mixture in submicron and nano scale size reveals the minor reduction of fracture toughness (up to 10%) at elevated temperature. Practical implications: The results show that using of powders in submicron and nano scale size not improve the tool life but influences the fracture toughness et elevated temperatures. Originality/value: The results of the presented investigations allow rational use of existing ceramic tools.