Phase formation during anneal of supersaturated TiB{sub 2}-CrB{sub 2}-WB{sub 2} solid solutions
- Institut fuer Gesteinshuettenkunde, Aachen (Germany)
Numerous transition metal diborides of AlB{sub 2} structure type reveal large mutual solid solubility. Temperature-depending homogeneity ranges bordering immiscibility gaps within the system TiB{sub 2}-CrB{sub 2}-WB{sub 2} provide the opportunity to tailor an in situ grown typical platelet-shaped phase emerging from a supersaturated host matrix. Results are presented where variations in composition, manufacturing parameters, and heat treatment lead to precipitates of a {open_quotes}W{sub 2}B{sub 5}{close_quotes} structure accompanied by the formation of another tungsten boride less rich in boron in a (Ti, W, Cr)B{sub 2} matrix. All phases are characterized by high melting points and hardness. The enhanced formation of the matrix as well as the precipitation mechanism were activated by the addition of 6 to 20 mule% CrB{sub 2} to the system TiB{sub 2}-WB{sub 2}. Within the ternary solid solution, a particular composition range exists exhibiting a thermal expansion behavior similar to boron carbide. Attempts are made to toughen boron and silicon carbide ceramics by processing this in situ growth of platelets out of dispersed transition metal diboride within a carbide matrix.
- OSTI ID:
- 569501
- Journal Information:
- Journal of Solid State Chemistry, Vol. 133, Issue 1; Other Information: PBD: Oct 1997
- Country of Publication:
- United States
- Language:
- English
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