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In order to improve the elevated temperature mechanical properties and modify the thermophysical properties of tungsten, tungsten matrix composites containing 30 vol.% zirconium carbide particles (ZrC/W) were prepared by vacuum hot-pressing at 2000 °C. Flexural strength of ZrC/W composites increases gradually with increasing temperature and reaches a maximum value at 1000 °C. The observation of the fracture characteristics of ZrC/W composites at various temperatures reveals that the excellent elevated temperature strength is attributed to the brittle–ductile transition in the tungsten matrix, which allows a more effective strengthening effect from the zirconium carbide particles. The elastic modulus decreases slightly with increasing temperature from room temperature to 1200 °C, and as a result of the addition of zirconium carbide particles the modulus of ZrC/W is higher than that of monolithic tungsten at all testing temperatures. The addition of zirconium carbide remarkably decreases the thermal conductivity of the composites. The unique combination of high melting point, good high temperature strength, high elastic modulus, and low thermal conductivity is very beneficial to the high temperature application of ZrC/W composites. [Copyright &y& Elsevier]

This work concerns the microstructure-mechanical properties relationship in Al 2 O 3 /SmAlO 3 composites prepared by hot pressing at temperatures from 1450 °C to 1650 °C. Dense samples have been prepared using co-precipitated trigonal α -Al 2 O 3 and orthorhombic SmAlO 3 at the pseudo-binary eutectic composition. The overall microstructure coarsens with increasing processing temperature, but the nanoscale precipitates within α -Al 2 O 3 and SmAlO 3 grains contribute to coherency strains and distortions in Al 2 O 3 /SmAlO 3 prepared at 1650 °C. The intragranular SmAlO 3 precipitates in Al 2 O 3 grains exhibit semi-coherent interface and an orientation relationship of the intragranular phase SmAlO 3 and alumina matrix close to two different zone axes, namely [ 2 3 ¯ 1 ] SmAlO 3 and [ 4 ¯ 401 ] Al 2 O 3 . Consequently, significant strengthening effect is found from the measured hardness values on the sample sintered at 1650 °C. The measured flexural strength and single edged notched beam fracture toughness of the Al 2 O 3 /SmAlO 3 ceramic are comparable to traditional secondary phases reinforced alumina composites. The sample sintered at 1500 °C exhibits a flexural strength of 558 MPa and a fracture toughness of 5.59 MPa⋅m1/2. [ABSTRACT FROM AUTHOR]

Crack-healing behavior and strength recovery of ZrO 2 (Y 2 O 3 )–Al 2 O 3 –MoSi 2 (TZ3Y20A–MoSi 2 ) ceramics have been investigated. Heat treatment in air enhances distinctly the flexural strength of TZ3Y20A–MoSi 2 ceramics. Si–O oxide and ZrSiO 4 are found after heat treatment, in which the former heals the cracks and recovers the strength, however, the latter is one kind of brittle materials that reduces mechanical performance of ceramics. The TZ3Y20A–10 vol% MoSi 2 ceramic has a complete crack-healing effect and strength recovery by suitable heat treatment at 1373 K for 3 h in air, however, the strength does not recover completely under other heat treatment conditions. With further increasing the MoSi 2 contents to 20 vol%, the flexural strength of as heat-treated TZ3Y20A–MoSi 2 ceramics is higher than that of pre-cracked specimens, but remains lower than that of smooth specimens. Crack closure and rebonding of the crack walls are due to the formation of Si–O glassy phase by oxidation reaction. [ABSTRACT FROM AUTHOR]