Tyranno SA3 fiber–ZrB2 composites. Part I: Microstructure and densification

Strength and toughness: The challenging case of TaC-based composites

“…Pressureless sintering of TaC-MoSi 2 system generally requires a temperature around 1950°C [11], but in this case it was set at 2100°C for 3 h in order to let the b ? a SiC polytypic transformation to completely occur.…”

“…a SiC polytypic transformation. MoSi 2 was selected as sintering aid in view of its role in favoring the densification through formation of transient liquid phases and of its refractoriness at high temperature [5,11]. Little amount of liquid phases formed at 2010°C, owing to the eutectic between MoSi 2 and SiC [16], certainly helped the local rearrangement and agglomeration of SiC rounded particles and favored their evolution to platelets leaving clean grain boundaries with the matrix.…”

“…Transition metal disilicides (MeSi 2 ) were added to Zr-, Hf-and Ta-borides and carbides mainly with the purpose of densification [5,11]. They cannot be considered as solely sintering aids because they significantly modify the microstructure and properties especially when their content is raised over some 5 vol% [5,11].…”

“…They cannot be considered as solely sintering aids because they significantly modify the microstructure and properties especially when their content is raised over some 5 vol% [5,11]. SiC addition to TaC was tested by Liu et al, who reported fracture toughness overpassing 6 MPa m 1/2 for addition of 20 vol% SiC particles [6].…”

“…However this additive, and silicides in general, cannot be used in combination with C fiber owing to an excessive reaction leading http://dx.doi.org/10.1016/j.compositesb.2014. 11.043 1359-8368/Ó 2014 Elsevier Ltd. All rights reserved.…”