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Forming of the structure and properties of composite material system LaB6-(Ti,Zr)B2

Varvara N. Paderno ,  Vladimir Filippov ,  Alfred Lyashchenko ,  Svitlana E. Polovets 

Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Krzizanovsky, Kyiv 38(044), Ukraine

Abstract
Previously, it was found [1] that the use of solid solutions diborides as a hardening phase in self reinforced composites based on lanthanum heksaboride significantly facilitates the formation of fibers phase of diboride in the eutectic alloy and increases the frequency of the eutectic structure and mechanical characteristics of materials.

In order to establish the regularities of formation of the structural state directed crystallized composite materials of this type, a detailed study of the microstructure of a wider on the composition of a set alloy of system LaB6-(TixZr1-x)B2 depending on the ratio of diboride components in the hardening phase (x) using methods of electron microscopy.

The results of investigation of feature of the structure of obtained samples alloy system LaB6-(TixZr1-x)B2 from the ratio Tі/Zr showed that in all cases persist the general trends formation of a regular whisker structure, and otherness is observed only in the degree of uniformity of distribution and fiber diameter of the reinforcing phase. Established, that the most evenly structure with uniform size of fibers formed in the ratio TiB2/ZrB2~3/2 in the solid solution.

Using solid solution diborides titanium-zirconium as a reinforcing phase allowed to obtain samples with varying degrees of discrepancy of parameters of crystal lattices of phases and a several different stress state in the composite due to smooth changes in the crystal lattice and thermal expansion coefficient in diboride phase depending on the ratio Tі/Zr.

It was found that the maximum value of the modulus of elasticity, which corresponds to the composition LaB6-(Ti0,6Zr0,4)B2, coincides with a maximum uniformity of the eutectic microstructure.

1.Paderno Yu., Paderno V., Filippov V. Some Peculiarities of Eutectic Crystallization of LaB6-(TixZr1-x) B2 Alloys / Jour. of Solid State Chem. 154, 165-167, 2000.

 

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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium I, by Svitlana E. Polovets
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-28 13:31
Revised:   2009-07-16 11:56