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Amorphous 5f Ferromagnetic Hydrides UH_{3}Mo_{x}

100%

Tkach I., Kim-Ngan N., Maškova S., Andreev A., Matěj Z., Havela L.

Acta Physica Polonica A

2014

vol. 126

issue 1

292-293

γ-U metal, stabilized down to room temperature in the bcc structure by Mo doping, can absorb hydrogen at high H_{2} pressures only. The product is amorphous hydride UH_{3}Mo_{x} analogous to β-UH_{3}. Such hydrides are ferromagnetic with high Curie temperatures (up to 200 K), enhanced with respect to β-UH_{3}. Magnetic moment of U also increases. Large disorder together with high anisotropy lead to a very high coercivity, reaching 4 T at low temperatures. As amorphization normally tends to suppress magnetic ordering of U compounds, such hydrides represent a new class of materials, amorphous U-based ferromagnets with relatively high Curie temperature.

Defects in Ultra-Fine Grained Mg and Mg-Based Alloys Prepared by High Pressure Torsion Studied by Positron Annihilation

84%

Čížek J., Procházka I., Smola B., Stulíková I., Kužel R., Matěj Z., Cherkaska V., Islamgaliev R., Kulyasova O.

Acta Physica Polonica A

2005

vol. 107

issue 5

738-744

Despite the favourable strength and thermal stability, a disadvantage of the Mg-based alloys consists in a low ductility. Recently it has been demonstrated that ultra fine grained metals with grain size around 100 nm can be produced by high pressure torsion. A number of ultra fine grained metals exhibit favourable mechanical properties consisting in a combination of a very high strength and a significant ductility. For this reason, it is highly interesting to examine microstructure and physical properties of ultra fine grained Mg-based light alloys. Following this purpose, microstructure investigations and defect studies of ultra fine grained pure Mg and ultra fine grained Mg-10%Gd alloy prepared by high pressure torsion were performed in the present work using positron annihilation spectroscopy combined with X-ray diffraction, TEM observations, and microhardness measurements. Positrons are trapped at dislocations in Mg and Mg-10%Gd alloy deformed by high pressure torsion. A number of dislocations increases with the radial distance r from the centre to the margin of the sample. No microvoids (small vacancy clusters) were detected. Mg-10%Gd alloy deformed by high pressure torsion exhibits a homogeneous ultra fine grained structure with a grain size around 100 nm and high dislocations density. On the other hand, pure Mg deformed by high pressure torsion exhibits a binomial type of structure which consists of "deformed regions" with ultra fine grained structure and a high dislocation density and dislocation-free "recovered regions" with large grains. It indicates a dynamic recovery of microstructure during high pressure torsion processing.

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2 Acta Physica Polonica A

1 2014

1 2005

2 Matěj Z.

1 Andreev A.

1 Cherkaska V.

1 Havela L.

1 Islamgaliev R.

1 Kim-Ngan N.

1 Kulyasova O.

1 Kužel R.

1 Maškova S.

1 Procházka I.

1 Smola B.

1 Stulíková I.

1 Tkach I.

1 Čížek J.

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Amorphous 5f Ferromagnetic Hydrides UH_{3}Mo_{x}

Defects in Ultra-Fine Grained Mg and Mg-Based Alloys Prepared by High Pressure Torsion Studied by Positron Annihilation