Nb and CrAl2O3 composites with interpenetrating networks

Processing and characterisation of three-layer alumina-based composites with enhanced damage tolerance

“…The three-layer Cr-Al/Al 2 O 3 //Fe-Al/Al 2 O 3 //Cr-Al/ Al 2 O 3 system (3L-Cr-A/Fe-A) was used for the following reasons: (i) Cr/Al 2 O 3 and Fe/Al 2 O 3 composites can be sintered to high density under basically the same sintering conditions, 12,13 (ii) the interfacial bond strength of Fe and Cr with Al 2 O 3 is high 14,15 and (iii) Cr has a lower thermal expansion coefficient than Fe allowing residual compressive stresses to be generated in the outer layers during cooling from sintering temperature. 16 …”

Cr-Al2O3 layered composites with a high electrical anisotropy prepared by repeated deformation processing

“…1 The addition of Al is thought to reduce the passivating oxide layers on the chromium surfaces during sintering, and in this way improve the densification. Depending on the total metal content, the composites' electrical resistivity can vary by several orders of magnitude.…”

Advanced Alumina Composites Reinforced with Nb-Based Alloys

“…Such composites can be produced by liquid melt infiltration, for example. With this technique, alumina-based composites with Cu [13] and Cr [14] as the reinforcing phase have been produced, which offer an enhanced fracture toughness of 6.2 MPa m 1/2 and 6.8 MPa m 1/2 , respectively. However, while the fracture strength of the Cr±Al 2 O 3 system compared with monolithic Al 2 O 3 is increased by a factor of about two up to 570 MPa, no enhancement of the fracture strength has been achieved for the Cu±Al 2 O 3 system.…”

“…For the fracture-toughness measurements, a Vickers indentation was used for crack initiation and the toughness was calculated using the ISB method [24] to get a rough estimate of the potential of toughness increase, especially compared with monolithic Al 2 O 3 , measured by the same technique [25] as well as literature data of similar composites. [14,25,26,29] Hardness (HV10) was obtained with a Vickers diamond indenter using a 100 N load and a loading time of 10 s. Wear resistance was investigated using a testing setup according to the Japanese Industry Standard JIS H8615, in which grinding paper (SiC 320 grid) is mounted on a stationary 12 mm-wide wheel that is loaded with 32 N and moved 30 mm back and forth on the surface of the specimen at a frequency of 1 Hz. After each double stroke, the wheel is turned by 0.9 to expose fresh grinding paper.…”

“…As expected, the wear resistance increases with the ceramic volume fraction. While the value for [14,25,26,29], K IC measured by SEPB [13,15] Obviously, this is also due to the strong interface bonding between the Nb-based (inter)metallic phase and Al 2 O 3 that prevents a break-off or pull-out of the ceramic component in the surface-near region. As expected, the continuous network of the (inter)metallic phase leads to electrical conductivity of the composites that increases with the ceramic volume fraction.…”