Thermochemical Deformation Behavior and Pre-stressed Strengthening of Al2O3-AlN Composite Ceramics
Al2O3-AlN composite ceramics have a wide range of applications in the field of electronic information.In order to ensure their service safety and reliability,the post-treatment reinforcement technique under the thermochemical deformation control was used to enhance mechanical properties of the composite ceramics.Non-contact in-situ deformation measurements,SEM-EDS,XRD and indentation tests were used to study thermochemical deformation behavior,phase-microstructure evolution and the prestress reinforcement mechanisms of the Al2O3-AlN composite ceramics.It is indicated that flexural strength of the Al2O3-AlN composite ceramics first increased and then decreased with increasing post-treatment temperature.Specifically,flexural strength of the sample post-treated at 1100 ℃ reached a maximum value of(519.23±23.87)MPa,which is 15％higher than that of the untreated sample.Meanwhile,thermal conductivity of the composite ceramics was not reduced by the post-treatment.The post-treatment process caused localized surface oxidation of AlN in the composite ceramics,accompanied by the volume expansion.Subsequently,residual compressive stress was produced on surface of the composite ceramics through the external and internal thermochemical deformation mismatch,which is favorite to the increasement of crack propagation resistance and the effective enhancement of mechanical strength of the composite ceramics.However,when the post-treatment temperature exceeds 1200 ℃,pores and microcracks were formed on the surface oxide layer,leading to a decrease in the mechanical strength of the composite ceramics.
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