Structure and properties of ceramet composites Hf – HfB: experiment and theory

Volodymyr A Makara 1Serhiy Chornobuk 1Valeriy V. Kartuzov 2Aik Khachatryan 2

1. Taras Shevchenko Kyiv National University, Faculty of Physics, Volodimirska Str., 64, Kyiv 01601, Ukraine
2. Institute for Problems in Materias Science (IPMS), 3, Krzhizhanivsky Str., Kiev 03680, Ukraine

Abstract

In this work a structure and mechanical properties of composition materials Hf – HfB,  got the method of a vacuum argon-arc melting is studied. Composition of the got specimens was studied by a X-ray analysis. A structure was probed the method of optical microscopy. A microhardness was measured on the device of PMT-3 at loading on indentor 1 N.

It is set that at the melting of powders of Hf and HfB2 a chemical reaction the result of which is disappearance of phase of HfB2 and formation of new phase of HfB flows between them. Thus, composition material of composition of Hf– HfB is formed.

At maintenance of HfB at the level of 10  % (wt.) formed materials with an eutecticum structure (Teut = 2163 K). At the increase of maintenance of HfB the structure of matrix type is formed: the needle-shaped including of ceramic phase of HfB is evenly placed in the metallic matrix of Hf.

The microhardness of the got materials substantially depends on composition of compos, evenly rising from 2 GPa (Hf) to 9,5 GPa (Hf – 29%(wt.) HfB)

For proof of existence of eutecticum in the system of Hf – HfB by quantum mechanical calculations a calculable experiment is conducted

On the basis of method of a priori pseudopotential calculated   energy of co-operation between the atoms of Hf – Hf,   between the molecules of HfB – HfB and similarly   between Hf – HfB. The parameters of grates  of Hf and HfB are calculated.

It is got, that energy of mixing of components, consequently, Hf and HfB in the system of Hf – HfB does not dissolve, and from a condition (T is  a temperature of existence of the system) follows, that Hf and HfB form an eutecticum alloy. From the condition of extremum of thermodynamics potential determine the characteristic parameters of the system in the point of eutecticum (temperature, concentration).

It is got, that a concentration of HfB is in the system of Hf–HfB = 26.3% (molar concentration) in the point of eutecticum, and temperature is T = 2173 K.

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Presentation: Oral at E-MRS Fall Meeting 2009, Symposium I, by Volodymyr A Makara
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-26 12:30
Revised:   2009-08-27 17:33
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