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1

Influence of Ceramic Nanoparticles on Thermal Stability of Ultra Fine Grained Copper

100%

Čížek J., Procházka I., Cieslar M., Islamgaliev R., Kulyasova O.

Acta Physica Polonica A

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2008

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vol. 113

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issue 5

1285-1292

EN

A detailed study of the bulk ultra fine grained pure copper and copper with Al_2O_3 particles was carried out in the present work. The specimens were prepared by the high-pressure torsion and their microstructure was investigated by positron lifetime spectroscopy combined with transmission electron microscopy and microhardness tests. Defects in the as-deformed materials were characterized and the thermal stability of the ultra fine grained microstructure was subsequently examined in annealing experiments. An addition of Al_2O_3 nanoparticles was found to improve significantly the thermal stability of the ultra fine grained structure, the optimum content of Al_2O_3 being ≈0.5 wt.%.

2

The Microstructure and Fatigue of Ultrafine-Grained Al-Cu-Mg Alloy

86%

Islamgaliev R., Khafizova E., Kulyasova O., Nesterov K., Ganeev A., Golubovskiy E., Volkov M.

Acta Physica Polonica A

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2015

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vol. 128

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issue 4

633-636

EN

In this work the influence of equal-channel angular pressing on strength and fatigue of an aluminum alloy has been studied. Transmission electron microscopy was applied to determine an average grain size, shape, and size of precipitates. The ultimate tensile strength and fatigue endurance limit of ultrafine-grained and coarse-grained samples were evaluated at 20°C and 175°C.

3

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

73%

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

Acta Physica Polonica A

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2005

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vol. 107

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issue 5

738-744

EN

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.

4

Ultra Fine-Grained Metals Prepared by Severe Plastic Deformation: A Positron Annihilation Study

59%

Čížek J., Procházka I., Kužel R., Matĕj Z., Cherkaska V., Cieslar M., Smola B., Stulíková I., Brauer G., Anwand W., Islamgaliev R., Kulyasova O.

Acta Physica Polonica A

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2005

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vol. 107

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issue 5

745-752

EN

Recent investigations of ultra fine-grained metals (Cu, Fe, Ni) performed within a Prague-Rossendorf-Ufa collaboration will be reviewed. The specimens were prepared by severe plastic deformation: the high-pressure torsion and equal channel angular pressing. Positron annihilation spectroscopy was used as the main method including (i) the conventional lifetime and the Doppler broadening measurements with ^{22}Na and (ii) the slow-positron implantation spectroscopy with the Doppler broadening measurement. Other methods were also involved: transmission electron microscopy, X-ray diffraction, and microhardness. First, the mean grain size was determined and defects were identified in the as-deformed materials. Defects concentration and spatial distribution were studied in detail. Dislocations situated in distorted regions along grain boundaries, and a few-vacancy clusters distributed homogeneously inside dislocations-free grains, were observed in the ultra fine-grained Cu, Fe, and Ni. Subsequently, the thermal evolution of the ultra fine-grained structures during isochronal annealing was studied.

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4 Acta Physica Polonica A

1 2015

1 2008

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4 Islamgaliev R.

4 Kulyasova O.

3 Procházka I.

3 Čížek J.

2 Cherkaska V.

2 Cieslar M.

2 Kužel R.

2 Smola B.

2 Stulíková I.

1 Anwand W.

1 Brauer G.

1 Ganeev A.

1 Golubovskiy E.

1 Khafizova E.

1 Matĕj Z.

1 Matěj Z.

1 Nesterov K.

1 Volkov M.

Influence of Ceramic Nanoparticles on Thermal Stability of Ultra Fine Grained Copper

The Microstructure and Fatigue of Ultrafine-Grained Al-Cu-Mg Alloy

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

Ultra Fine-Grained Metals Prepared by Severe Plastic Deformation: A Positron Annihilation Study