The improvement of the fracture toughness at room temperature of Mo-sintered material, which is heat-resisting, is strongly required in service. One of improving methods is fabrication of a composite material with dispersion strengthening secondary particles. Therefore, we pointed out previously that ZrO
2, as these secondary particles, was excellent from a standpoint of the utilization as a heat-resisting material and the effect of sintering characteristics and t→m phase transformation on toughness.
The aim of this investigation is to study experimentally the mechanical properties of Mo-ZrO
2 sintered composites, i.e. Young’s modulus, bending strength and fracture toughness, and to understand the effect of ZrO
2 on the mechanical properties of this material.
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oindentThe results are summarized as follows:
(1) Young’s modulus of Mo-ZrO
2 composite material decreases with increase in the volume fraction of ZrO
2 and agrees well with the results of theoretical prediction based on the self-consistent method, as far as the ZrO
2 content does not exceed 20 vol%.
(2) The size of transformation zone of ZrO
2 in the vicinity of fracture surface is about 3.0-4.0 μm in maximum, and this maximum size depends on the volume fraction of ZrO
2.
(3) The volume fraction of ZrO
2 has a great influence on the bending strength and fracture toughness. That is, the former reaches a maximum value in case of specimens containing 12.5-15.0 vol% ZrO
2 and decreases with increase of ZrO
2 content.
(4) The increment of toughness may be explained by the contribution of the effect of t→m stress induced phase transformation of ZrO
2.
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