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Four composites, MoSi 2+ZrO 2, MoSi 2+ZrO 2(Y 2O 3), MoSi 2+ZrO 2+SiC and MoSi 2+ZrO 2(Y 2O 3)+SiC are fabricated by mechanical alloying. It is clear that cracks produced on the MoSi 2 matrix composites during hardness testing belong to the Palmquist crack system. The value of highest fracture toughness of MoSi 2+ZrO 2+SiC composite is 7.58?MPa·m 1/2 , which is nearly three times that of monolithic MoSi 2. This can be attributed to well distributed ZrO 2 and SiC particles along the boundaries of very fine MoSi 2 grains.
It is clear that four composites, MoSi 2 + ZrO 2, MoSi 2 + ZrO 2 (Y 2O 3), MoSi 2 + ZrO 2 + SiC and MoSi 2 + ZrO 2 (Y 2O 3) + SiC are fabricated that all that. cracks produced on the MoSi 2 matrix composites during hardness testing belong to the Palmquist crack system. The value of highest fracture toughness of MoSi 2 + ZrO 2 + SiC composite is 7.58 · MPa · m 1/2, which is nearly three times that of monolithic MoSi 2. This can be attributed to well distributed ZrO 2 and SiC particles along the boundaries of very fine MoSi 2 grains.