The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those o...The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those obtained by singte edge notched beam (SENB) technique. Experimental results show that the KIC (IM) values calculated with different equations are quite different one from another. For composites without phase transformable components the KIC (IM) and KIC (SENB) values are practically on the same level, but for composites with phase transformable components (partially stabilized zirconia) the KIC (SENB) values are always higher than KIC (IM). This is because that the IM method can not reveal sensitively the toughening effect due to dynamic t-m transformation of ZrO2 as the SENB method does. The accuracy of the IM method depends on the Suitability of the IM equations and was evaluated for the materials used in this investigation. Two new IM equations are suggested with which the KIC (IM ) values can be obtained very close to KIC (SENB) values for composites having phase transformable components.展开更多
By using self-made metal-alkoxide yttrium isopropoxide as a sintering additive and disperser of whisker, the SiC whisker reinforced AIN ceramics was prepared. Its apparent density is 99.5 percent of the theoretical de...By using self-made metal-alkoxide yttrium isopropoxide as a sintering additive and disperser of whisker, the SiC whisker reinforced AIN ceramics was prepared. Its apparent density is 99.5 percent of the theoretical density; its flexural strength and fracture toughness are 681 MPa and 5.21 MPa·m1/2 respectively. Comparing the result with that by applying Y2O3 powder as a sintering additive, the flexural strength is increased by 25% and the fracture toughness is increased by 33% . The dispersity of whisker by increased yttrium isopropoxide is significantly better than that by Triton X-100.展开更多
文摘The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those obtained by singte edge notched beam (SENB) technique. Experimental results show that the KIC (IM) values calculated with different equations are quite different one from another. For composites without phase transformable components the KIC (IM) and KIC (SENB) values are practically on the same level, but for composites with phase transformable components (partially stabilized zirconia) the KIC (SENB) values are always higher than KIC (IM). This is because that the IM method can not reveal sensitively the toughening effect due to dynamic t-m transformation of ZrO2 as the SENB method does. The accuracy of the IM method depends on the Suitability of the IM equations and was evaluated for the materials used in this investigation. Two new IM equations are suggested with which the KIC (IM ) values can be obtained very close to KIC (SENB) values for composites having phase transformable components.
文摘By using self-made metal-alkoxide yttrium isopropoxide as a sintering additive and disperser of whisker, the SiC whisker reinforced AIN ceramics was prepared. Its apparent density is 99.5 percent of the theoretical density; its flexural strength and fracture toughness are 681 MPa and 5.21 MPa·m1/2 respectively. Comparing the result with that by applying Y2O3 powder as a sintering additive, the flexural strength is increased by 25% and the fracture toughness is increased by 33% . The dispersity of whisker by increased yttrium isopropoxide is significantly better than that by Triton X-100.
