Toughening and strengthening of advanced ceramics with rare earth additives

Al2O3/(W,Ti)C composite ceramic materials reinforced by rare earth additives have been fabricated by the hot pressing technique. Microstructure, flexural strength, toughening and strengthening mechanisms are analyzed. The maximum flexural strength and fracture toughness of the yttrium reinforced Al2O3/(W,Ti)C ceramic are 853 MPa and 6.1 MPam1/2, respectively, which are approximately 20% and 16% higher than for the corresponding material without yttrium. Acting mechanisms of the yttrium additive are mainly the purification of interface, the subsequent increase in the interface bonding strength and strengthening by nanometer sized particles. Because of the co-existence of both strong and weak interfaces, synergistic interactions of toughening mechanisms like crack bridging, crack branching, crack defection and microcracking, etc. are enhanced. Therefore, fracture toughness of the rare earth reinforced Al2O3/(W,Ti)C ceramic material is increased. The developed new ceramic materials are found to achieve higher fracture resistance when used as cutting tools.