| As a novel machinable ceramic material, CePO4/ZrO2 composites have been widely used owning to their chemical stability, high melting point, excellent oxidation resistance and weak interfaces bonding. These composites could be machinable through formation and linking of cracks at weak interfaces between the two phase. The composites can be machined using conventional metal-working methods. However, the research about these systems is inadequate.In this paper, Ce-ZrO2 and (Ce,Y)-ZrO2 are mixed with different CePO4 content by mechanical milling method, followed by dry pressing and CIP(cold isostatic press). The green body is sintered under different temperature.Hardness, flexural strength and fracture toughness of the materials with different CePO4 content(15%-35%) were compared, varying sintering temperature (1400℃-1600℃). Compared with CePO4/(Ce,Y)-ZrO2 material, mechanical properties of CePO4/Ce-ZrO2 material are improved. For CePO4/Ce-ZrO2 material sintered at 1550℃, the optimum content of CePO4 is determined as 25%, with the optimum mechanical properties Hv=7.06GPa, δ =457.05MPa, KIC=9.47MPa·m1/2. Mechanical properties of CePO4/(Ce,Y)-ZrO2 material pressed on 100MPa are better than 11.3MPa.The microstructure of materials was investigated using XRD, SEM, EPMA(electron probe microanalysis). The results indicate that new phases are formed during sintering process, attributing to solid reaction on high temperature. The CePO4 particles are well dispersed in the ZrO2 matrix. The fracture mode is the mixture of intergranular fracture and transgranular fracture, occasionally with some grains pulling out. Because of the weak interfaces between ZrO2 and CePO4, the propagation mechanism of indentation cracks changes and took the discontinuous form instead of the continuous form, and microcracks are formed at weak interfaces under external force.In the paper, machining exponent is used to characterize machinability. The... |
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