题  目：Ductile deformation and fracture behaviour in alumina/silicon carbide nanocomposites

报告人：Dr. Houzheng Wu

 

时  间：7月28日（周二） 10:30-11:50

地  点：李薰楼468会议室

 

报告摘要：It has been noticed that, compared to the monolithic alumina ceramics with the same grain size, alumina polycrystals containing small fractions (typically 1-5vol%) of tens to hundreds nanometers of silicon carbide particles (widely called alumina/silicon carbide nanocomposites) are able to show significant increments in strength. Any increase in strength, however, is not accompanied by a corresponding increase in fracture toughness. It has therefore been proposed that the surface properties of alumina/silicon carbide nanocomposites are the key to their enhanced strength. In the past years, we have studied the near surface damage (ductile deformation and micro-fracture) of alumina/silicon carbide nanocomposites using various characterizing techniques, such as TEM, FIB, fluorescence spectroscopy, grazing-incidence X-ray powder diffraction, and Hertzian indentation. It has been demonstrated that dislocations are dominant deformation features in the nanocomposites while twins are prevalent in monolithic alumina in ductile regions after pseudo-static compressive loading. The difference in ductile deformation, and fracture mode, leads to a significant difference in residual compression in the near-surface and a transition in fracture mode on ground or worn surfaces. In this talk, I am going to summarise the research outcomes generated from different characterisation techniques, and to speculate the potential benefits of ceramic nanocomposites.