Jeno Gubicza - Academia.edu (original) (raw)

Papers by Jeno Gubicza

Variety of experimental tools have been used for characterization of morphology of magnetic nanop... more Variety of experimental tools have been used for characterization of morphology of magnetic nanoparticles in colloid suspensions. Ferric oxide particles of sizes between 5 and 20 nm have been prepared by different methods, aqueous co-precipitation of ferrous salts, thermal decomposition of metal complexes in organic solvents, and using mechanical milling of micron sized particles. They were covered by stabilizing layer of different surfactants and dispersed in organic solvents. The analysis and comparison of the collected data allowed to assess the performance of each technique and give recommendations for obtaining precise structural data for nanoparticles dispersions of the given size range.

Materials Science Forum, 2005

A commercial Al-Mg-Si alloy (Al 6082) was deformed by Equal-Channel Angular Pressing (ECAP) to pr... more A commercial Al-Mg-Si alloy (Al 6082) was deformed by Equal-Channel Angular Pressing (ECAP) to produce bulk ultrafine-grained microstructure. The crystallite size distribution and the characteristic parameters of the dislocation structure were investigated by X-ray diffraction profile analysis. It was found that the crystallite size decreased and the dislocation density increased during ECAP deformation. The increase of the yield stress of the alloy was related to the increase of the dislocation density using the Taylor model. Materials Science Forum Vols. 473-474 (2005) pp. 453-458 online at http://www.scientific.net

The effect of the nominal Mg content and the milling time on the microstructure and the hardness ... more The effect of the nominal Mg content and the milling time on the microstructure and the hardness of mechanically alloyed Al (Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis and the hardness is obtained from depth sensing indentation test. Magnesium gradually goes into solid solution during ball milling and after about 3 h almost complete solid solution state is attained up to the nominal Mg content of the alloys. With increasing milling time the dislocation density, the hardness and the Mg content in solid solution are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for long milling period the dislocation density slightly decreases together with a slight reduction of the hardness.

IOP Conference Series: Materials Science and Engineering, 2014

Supersaturated Cu -3 at.% Ag alloy was processed by rolling at liquid nitrogen temperature and su... more Supersaturated Cu -3 at.% Ag alloy was processed by rolling at liquid nitrogen temperature and subsequent annealing at 623 K up to 20 min. It was found that after annealing, an inhomogeneous solute atom distribution developed, since the Ag particles with small size and/or large specific interfacial energy were dissolved due to the Gibbs-Thomson effect. In the region where the solute concentration increased, a high dislocation density was retained in the Cu matrix even after annealing, while in the region where the Ag solute content did not increase, the dislocation density decreased by more than one order of magnitude. Therefore, in the cryorolled and annealed samples, heterogeneous microstructures were developed where both the dislocation density and the solute concentration varied considerably.

Zeitschrift für Kristallographie Supplements, 2006

Two essentially different materials, cubic Ti 49.8 Ni 50.2 shape memory alloy and hexagonal AZ91 ... more Two essentially different materials, cubic Ti 49.8 Ni 50.2 shape memory alloy and hexagonal AZ91 Mg alloy, were deformed by equal channel angular pressing (ECAP). The microstructure developed as a result of severe plastic deformation was studied by X-ray line profile analysis. The correlation between the microstructure and the mechanical behavior was also investigated. Below 100 °C the tensile strength of the Mg alloy increased as a consequence of the increase of the dislocation density owing to ECAP. Above 200 °C the strength decreased and the ductility increased as a result of the breakage of the Al 12 Mg 17 precipitates due to ECAP. The analysis of the dislocation contrast factors of Ti 49.8 Ni 50.2 revealed that <100>{110} dislocations with <111> line vector formed during ECAP.

The review is devoted to a study of interface phenomena influencing advanced properties of nanosc... more The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materiais processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by transmission electron microscopy (TEM), high-resolution X-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studi...

International Journal of Plasticity

A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly text... more A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly textured cast magnesium is presented. An elasto-plastic self-consistent model (EPSC) is used to model the dislocation slip and twinning activity, respectively. The results are quantitatively compared with experimental data obtained by in-situ neutron diffraction (ND) and acoustic emission (AE). Both EPSC calculations and ND line profile analysis show an increased activity of prismatic slip with increasing strain and a loading mode dependence of the activation of the second-order pyramidal slip. The AE measurements and the modeling indicate a difference in the number of nucleated twin variants and the twinned volume in tension and compression.

A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly text... more A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly textured cast magnesium is presented. An elasto-plastic self-consistent model (EPSC) is used to model the dislocation slip and twinning activity, respectively. The results are quantitatively compared with experimental data obtained by in-situ neutron diffraction (ND) and acoustic emission (AE). Both EPSC calculations and ND line profile analysis show an increased activity of prismatic slip with increasing strain and a loading mode dependence of the activation of the second-order pyramidal slip. The AE measurements and the modeling indicate a difference in the number of nucleated twin variants and the twinned volume in tension and compression.

Journal of Solid State Electrochemistry, 2015

Electrochemical and morphological properties of thin poly(3,4-ethylenedioxy-thiophene) (PEDOT) fi... more Electrochemical and morphological properties of thin poly(3,4-ethylenedioxy-thiophene) (PEDOT) films deposited on gold were investigated in aqueous sulfuric acid solutions. X-ray diffraction and electron microscopy were used for monitoring the morphological changes and structure evolution caused by overoxidation. The diffraction peaks of PEDOT became sharper and more intensive during the subsequent oxidation cycles. This indicates that besides the degradation of the PEDOT film, its crystallinity was gradually improved with increasing the number of oxidation cycles. These changes may result in the appearance of novel properties that may be advantageous for specific applications.

a. Tömbi nanoszerkezetű anyagok vizsgálata során kísérleti és gyártási tapasztalatot szereztünk f... more a. Tömbi nanoszerkezetű anyagok vizsgálata során kísérleti és gyártási tapasztalatot szereztünk fémekkel és ötvözeteikkel kapcsolatban. b. A nanoszerkezet előállítása során mechanikai, finomszerkezeti röntgen és elektronmikroszkópos vizsgálatokkal meghatároztuk az anyag makroszkópikus és mikroszkópikus jellemzőit. Konstitutív egyenletet dolgoztunk ki az anizotróp viselkedés leírására. c. A nanoszerkezetű anyagok előállítását követően vizsgáltuk a technológiai feldolgozhatóságukat a továbbalakítás, a forgácsolás és a hegesztés területén. d. A gyártási folyamatok mechanikai sémájának feltárása érdekében végeselemes modelleket készítettünk a különböző intenzív képlékenyalakítási eljárásokról. Kontinuumechanikai alapon elemeztük a nanoszerkezet kialakulásának feltételeit. e. A kutatások megalapozták a különleges tulajdonsággal rendelkező tömbi nanoszerkezetű anyagok laboratóriumot meghaladó, félüzemi előállítását. | a. During the investigation of bulk nanostructured materials we have go...

Zeitschrift für Kristallographie Supplements, 2006

Copper specimens were deformed by equal channel angular pressing (ECAP) up to 8 passes. The micro... more Copper specimens were deformed by equal channel angular pressing (ECAP) up to 8 passes. The microstructure was studied by X-ray line profile analysis. The crystallite size is reduced to a few tens of nanometers even after the first ECAP pass and it does not change significantly during further deformation. At the same time, the dislocation density increases gradually up to 4 ECAP passes. The thermal stability of the microstructure is examined by differential scanning calorimetry (DSC). The temperature of the DSC peak decreases whereas the stored energy increases with increasing strain. At the beginning of the heat release a bimodal grain structure develops indicated by a special double-peak shape of the diffraction line profiles.

Periodica Polytechnica, Mechanical Engineering

Al 7075 alloy was equal and differential speed rolled accord-ing to various deformation routes. I... more Al 7075 alloy was equal and differential speed rolled accord-ing to various deformation routes. In these routes the sheets were rotated around different axes between subsequent passes of rolling. The mechanical properties and the microstructure of the specimens processed by various routes were compared. It was found that while the strength values were irrespective of the rolling routes, the ductility depends strongly on the deformation method. The differences in the mechanical behavior were ex-plained by the edge/screw character in the dislocation structure. 1 Introduction The reduction of grain size in polycrystalline metallic ma-terials usually has a beneficial effect on mechanical proper-ties resulting in high strength, low temperature of ductile-to-brittle transition or improved superplastic formability [1–4]. Se-vere plastic deformation (SPD) techniques are effective methods in grain refinement without producing contamination or large porosity in the ultrafine grained microstru...

Powder Diffraction, 2005

Crystallite size determined by X-ray line profile analysis is often smaller than the grain or sub... more Crystallite size determined by X-ray line profile analysis is often smaller than the grain or subgrain size obtained by transmission electron microscopy, especially when the material has been produced by plastic deformation. It is shown that besides differences in orientation between grains or subgrains, dipolar dislocation walls without differences in orientation also break down coherency of X-rays scattering. This means that the coherently scattering domain size provided by X-ray line profile analysis provides subgrain or cell size bounded by dislocation boundaries or dipolar walls.

Materials Science Forum, 2004

The effect of the nominal Mg content and the milling time on the microstructure of mechanically a... more The effect of the nominal Mg content and the milling time on the microstructure of mechanically alloyed Al(Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. Magnesium gradually goes into solid solution during ball milling and after 3 h almost all of the Mg atoms are soluted into the Al matrix. With increasing milling time the Mg content in solid solution, the dislocation density as well as the hardness are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for a long milling period the dislocation density slightly decreases together with a slight reduction of the hardness.

Journal of Materials Science, 2014

Quenched and slowly cooled (annealed) Cu-0.7 %Cr, Cu-0.9 %Hf, and Cu-0.7 %Cr-0.9 %Hf alloys were ... more Quenched and slowly cooled (annealed) Cu-0.7 %Cr, Cu-0.9 %Hf, and Cu-0.7 %Cr-0.9 %Hf alloys were processed by high pressure torsion (HPT). The microstructures of the alloys were studied immediately after HPT and subsequent annealing. It has been shown that the microhardness and the thermal stability of the severely deformed microstructure increase, while the average grain size decreases in the order of Cu-0.7 %Cr, Cu-0.9 %Hf, and Cu-0.7 %Cr-0.9 %Hf alloys. The microhardness in all alloys is higher after quenching and HPT, than after annealing and HPT. The largest dislocation density is achieved by quenching and HPT in Hf-containing samples. Cu 5 Hf phase precipitations in Hf-containing alloys are more effective in retarding grain growth in comparison with Cr particles and lead to additional hardening during aging. It has been demonstrated that HPT-processing with subsequent heat-treatment might yield the combination of large hardness and high electrical conductivity in Cu alloys.

Materials Science and Engineering: A, 2010

A reduction of the stored energy in Cu processed by equal-channel angular pressing was observed a... more A reduction of the stored energy in Cu processed by equal-channel angular pressing was observed after 4 years of storage at room temperature. It was found that the decrease of stored energy was most probably caused by the loss of excess vacancies.

Materials Letters, 2015

Ultrafine-grained (UFG) microstructures in Cu-Cr alloys were processed by high pressure torsion (... more Ultrafine-grained (UFG) microstructures in Cu-Cr alloys were processed by high pressure torsion (HPT). The improved hardness was accompanied by a reduced electrical conductivity due to the large amount of grain boundaries. The effect of heat-treatment after HPT-processing on the hardness and the electrical conductivity was studied for different chromium contents (0.75, 9.85 and 27 wt%). For low Cr concentration (0.75%) the electrical conductivity increased considerably above 250 1C, however the hardness decreased concomitantly. At the same time, for high Cr content (9.85% and 27%) the hardness was only slightly reduced even at 500 1C, while the electrical conductivity increased to a similar level as before HPT due to grain boundary relaxation and decomposition of Cu-Cr solid solution. Our study demonstrates the capability of SPD-processing and subsequent heat-treatment to achieve a combination of high strength and good electrical conductivity.

Materials Science Forum, 2003

Materials Science and Engineering: A, 2015

A commercial MgAlZn alloy (AZ31) was processed by high pressure torsion (HPT) at room temperature... more A commercial MgAlZn alloy (AZ31) was processed by high pressure torsion (HPT) at room temperature, resulting in an extreme microstructure refinement down to the grain size of 150-250 nm. The microstructure evolution during HPT was investigated by transmission electron microscopy and X-ray diffraction line profile analysis. The microhardness was measured as a function of the distance from the center of the disk and the number of HPT revolutions. The detailed analysis of dislocation contrast factors in X-ray diffraction line profiles enables to determine the population of the different slip systems as a function of the imposed strain. The influence of microstructure and defect structure evolution on microhardness is discussed in detail.

Variety of experimental tools have been used for characterization of morphology of magnetic nanop... more Variety of experimental tools have been used for characterization of morphology of magnetic nanoparticles in colloid suspensions. Ferric oxide particles of sizes between 5 and 20 nm have been prepared by different methods, aqueous co-precipitation of ferrous salts, thermal decomposition of metal complexes in organic solvents, and using mechanical milling of micron sized particles. They were covered by stabilizing layer of different surfactants and dispersed in organic solvents. The analysis and comparison of the collected data allowed to assess the performance of each technique and give recommendations for obtaining precise structural data for nanoparticles dispersions of the given size range.

Materials Science Forum, 2005

A commercial Al-Mg-Si alloy (Al 6082) was deformed by Equal-Channel Angular Pressing (ECAP) to pr... more A commercial Al-Mg-Si alloy (Al 6082) was deformed by Equal-Channel Angular Pressing (ECAP) to produce bulk ultrafine-grained microstructure. The crystallite size distribution and the characteristic parameters of the dislocation structure were investigated by X-ray diffraction profile analysis. It was found that the crystallite size decreased and the dislocation density increased during ECAP deformation. The increase of the yield stress of the alloy was related to the increase of the dislocation density using the Taylor model. Materials Science Forum Vols. 473-474 (2005) pp. 453-458 online at http://www.scientific.net

The effect of the nominal Mg content and the milling time on the microstructure and the hardness ... more The effect of the nominal Mg content and the milling time on the microstructure and the hardness of mechanically alloyed Al (Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis and the hardness is obtained from depth sensing indentation test. Magnesium gradually goes into solid solution during ball milling and after about 3 h almost complete solid solution state is attained up to the nominal Mg content of the alloys. With increasing milling time the dislocation density, the hardness and the Mg content in solid solution are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for long milling period the dislocation density slightly decreases together with a slight reduction of the hardness.

IOP Conference Series: Materials Science and Engineering, 2014

Supersaturated Cu -3 at.% Ag alloy was processed by rolling at liquid nitrogen temperature and su... more Supersaturated Cu -3 at.% Ag alloy was processed by rolling at liquid nitrogen temperature and subsequent annealing at 623 K up to 20 min. It was found that after annealing, an inhomogeneous solute atom distribution developed, since the Ag particles with small size and/or large specific interfacial energy were dissolved due to the Gibbs-Thomson effect. In the region where the solute concentration increased, a high dislocation density was retained in the Cu matrix even after annealing, while in the region where the Ag solute content did not increase, the dislocation density decreased by more than one order of magnitude. Therefore, in the cryorolled and annealed samples, heterogeneous microstructures were developed where both the dislocation density and the solute concentration varied considerably.

Zeitschrift für Kristallographie Supplements, 2006

Two essentially different materials, cubic Ti 49.8 Ni 50.2 shape memory alloy and hexagonal AZ91 ... more Two essentially different materials, cubic Ti 49.8 Ni 50.2 shape memory alloy and hexagonal AZ91 Mg alloy, were deformed by equal channel angular pressing (ECAP). The microstructure developed as a result of severe plastic deformation was studied by X-ray line profile analysis. The correlation between the microstructure and the mechanical behavior was also investigated. Below 100 °C the tensile strength of the Mg alloy increased as a consequence of the increase of the dislocation density owing to ECAP. Above 200 °C the strength decreased and the ductility increased as a result of the breakage of the Al 12 Mg 17 precipitates due to ECAP. The analysis of the dislocation contrast factors of Ti 49.8 Ni 50.2 revealed that <100>{110} dislocations with <111> line vector formed during ECAP.

The review is devoted to a study of interface phenomena influencing advanced properties of nanosc... more The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materiais processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by transmission electron microscopy (TEM), high-resolution X-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studi...

International Journal of Plasticity

A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly text... more A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly textured cast magnesium is presented. An elasto-plastic self-consistent model (EPSC) is used to model the dislocation slip and twinning activity, respectively. The results are quantitatively compared with experimental data obtained by in-situ neutron diffraction (ND) and acoustic emission (AE). Both EPSC calculations and ND line profile analysis show an increased activity of prismatic slip with increasing strain and a loading mode dependence of the activation of the second-order pyramidal slip. The AE measurements and the modeling indicate a difference in the number of nucleated twin variants and the twinned volume in tension and compression.

A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly text... more A detailed analysis of the loading mode dependence of the deformation mechanisms in randomly textured cast magnesium is presented. An elasto-plastic self-consistent model (EPSC) is used to model the dislocation slip and twinning activity, respectively. The results are quantitatively compared with experimental data obtained by in-situ neutron diffraction (ND) and acoustic emission (AE). Both EPSC calculations and ND line profile analysis show an increased activity of prismatic slip with increasing strain and a loading mode dependence of the activation of the second-order pyramidal slip. The AE measurements and the modeling indicate a difference in the number of nucleated twin variants and the twinned volume in tension and compression.

Journal of Solid State Electrochemistry, 2015

Electrochemical and morphological properties of thin poly(3,4-ethylenedioxy-thiophene) (PEDOT) fi... more Electrochemical and morphological properties of thin poly(3,4-ethylenedioxy-thiophene) (PEDOT) films deposited on gold were investigated in aqueous sulfuric acid solutions. X-ray diffraction and electron microscopy were used for monitoring the morphological changes and structure evolution caused by overoxidation. The diffraction peaks of PEDOT became sharper and more intensive during the subsequent oxidation cycles. This indicates that besides the degradation of the PEDOT film, its crystallinity was gradually improved with increasing the number of oxidation cycles. These changes may result in the appearance of novel properties that may be advantageous for specific applications.

a. Tömbi nanoszerkezetű anyagok vizsgálata során kísérleti és gyártási tapasztalatot szereztünk f... more a. Tömbi nanoszerkezetű anyagok vizsgálata során kísérleti és gyártási tapasztalatot szereztünk fémekkel és ötvözeteikkel kapcsolatban. b. A nanoszerkezet előállítása során mechanikai, finomszerkezeti röntgen és elektronmikroszkópos vizsgálatokkal meghatároztuk az anyag makroszkópikus és mikroszkópikus jellemzőit. Konstitutív egyenletet dolgoztunk ki az anizotróp viselkedés leírására. c. A nanoszerkezetű anyagok előállítását követően vizsgáltuk a technológiai feldolgozhatóságukat a továbbalakítás, a forgácsolás és a hegesztés területén. d. A gyártási folyamatok mechanikai sémájának feltárása érdekében végeselemes modelleket készítettünk a különböző intenzív képlékenyalakítási eljárásokról. Kontinuumechanikai alapon elemeztük a nanoszerkezet kialakulásának feltételeit. e. A kutatások megalapozták a különleges tulajdonsággal rendelkező tömbi nanoszerkezetű anyagok laboratóriumot meghaladó, félüzemi előállítását. | a. During the investigation of bulk nanostructured materials we have go...

Zeitschrift für Kristallographie Supplements, 2006

Copper specimens were deformed by equal channel angular pressing (ECAP) up to 8 passes. The micro... more Copper specimens were deformed by equal channel angular pressing (ECAP) up to 8 passes. The microstructure was studied by X-ray line profile analysis. The crystallite size is reduced to a few tens of nanometers even after the first ECAP pass and it does not change significantly during further deformation. At the same time, the dislocation density increases gradually up to 4 ECAP passes. The thermal stability of the microstructure is examined by differential scanning calorimetry (DSC). The temperature of the DSC peak decreases whereas the stored energy increases with increasing strain. At the beginning of the heat release a bimodal grain structure develops indicated by a special double-peak shape of the diffraction line profiles.

Periodica Polytechnica, Mechanical Engineering

Al 7075 alloy was equal and differential speed rolled accord-ing to various deformation routes. I... more Al 7075 alloy was equal and differential speed rolled accord-ing to various deformation routes. In these routes the sheets were rotated around different axes between subsequent passes of rolling. The mechanical properties and the microstructure of the specimens processed by various routes were compared. It was found that while the strength values were irrespective of the rolling routes, the ductility depends strongly on the deformation method. The differences in the mechanical behavior were ex-plained by the edge/screw character in the dislocation structure. 1 Introduction The reduction of grain size in polycrystalline metallic ma-terials usually has a beneficial effect on mechanical proper-ties resulting in high strength, low temperature of ductile-to-brittle transition or improved superplastic formability [1–4]. Se-vere plastic deformation (SPD) techniques are effective methods in grain refinement without producing contamination or large porosity in the ultrafine grained microstru...

Powder Diffraction, 2005

Crystallite size determined by X-ray line profile analysis is often smaller than the grain or sub... more Crystallite size determined by X-ray line profile analysis is often smaller than the grain or subgrain size obtained by transmission electron microscopy, especially when the material has been produced by plastic deformation. It is shown that besides differences in orientation between grains or subgrains, dipolar dislocation walls without differences in orientation also break down coherency of X-rays scattering. This means that the coherently scattering domain size provided by X-ray line profile analysis provides subgrain or cell size bounded by dislocation boundaries or dipolar walls.

Materials Science Forum, 2004

The effect of the nominal Mg content and the milling time on the microstructure of mechanically a... more The effect of the nominal Mg content and the milling time on the microstructure of mechanically alloyed Al(Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. Magnesium gradually goes into solid solution during ball milling and after 3 h almost all of the Mg atoms are soluted into the Al matrix. With increasing milling time the Mg content in solid solution, the dislocation density as well as the hardness are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for a long milling period the dislocation density slightly decreases together with a slight reduction of the hardness.

Journal of Materials Science, 2014

Quenched and slowly cooled (annealed) Cu-0.7 %Cr, Cu-0.9 %Hf, and Cu-0.7 %Cr-0.9 %Hf alloys were ... more Quenched and slowly cooled (annealed) Cu-0.7 %Cr, Cu-0.9 %Hf, and Cu-0.7 %Cr-0.9 %Hf alloys were processed by high pressure torsion (HPT). The microstructures of the alloys were studied immediately after HPT and subsequent annealing. It has been shown that the microhardness and the thermal stability of the severely deformed microstructure increase, while the average grain size decreases in the order of Cu-0.7 %Cr, Cu-0.9 %Hf, and Cu-0.7 %Cr-0.9 %Hf alloys. The microhardness in all alloys is higher after quenching and HPT, than after annealing and HPT. The largest dislocation density is achieved by quenching and HPT in Hf-containing samples. Cu 5 Hf phase precipitations in Hf-containing alloys are more effective in retarding grain growth in comparison with Cr particles and lead to additional hardening during aging. It has been demonstrated that HPT-processing with subsequent heat-treatment might yield the combination of large hardness and high electrical conductivity in Cu alloys.

Materials Science and Engineering: A, 2010

A reduction of the stored energy in Cu processed by equal-channel angular pressing was observed a... more A reduction of the stored energy in Cu processed by equal-channel angular pressing was observed after 4 years of storage at room temperature. It was found that the decrease of stored energy was most probably caused by the loss of excess vacancies.

Materials Letters, 2015

Ultrafine-grained (UFG) microstructures in Cu-Cr alloys were processed by high pressure torsion (... more Ultrafine-grained (UFG) microstructures in Cu-Cr alloys were processed by high pressure torsion (HPT). The improved hardness was accompanied by a reduced electrical conductivity due to the large amount of grain boundaries. The effect of heat-treatment after HPT-processing on the hardness and the electrical conductivity was studied for different chromium contents (0.75, 9.85 and 27 wt%). For low Cr concentration (0.75%) the electrical conductivity increased considerably above 250 1C, however the hardness decreased concomitantly. At the same time, for high Cr content (9.85% and 27%) the hardness was only slightly reduced even at 500 1C, while the electrical conductivity increased to a similar level as before HPT due to grain boundary relaxation and decomposition of Cu-Cr solid solution. Our study demonstrates the capability of SPD-processing and subsequent heat-treatment to achieve a combination of high strength and good electrical conductivity.

Materials Science Forum, 2003

Materials Science and Engineering: A, 2015

A commercial MgAlZn alloy (AZ31) was processed by high pressure torsion (HPT) at room temperature... more A commercial MgAlZn alloy (AZ31) was processed by high pressure torsion (HPT) at room temperature, resulting in an extreme microstructure refinement down to the grain size of 150-250 nm. The microstructure evolution during HPT was investigated by transmission electron microscopy and X-ray diffraction line profile analysis. The microhardness was measured as a function of the distance from the center of the disk and the number of HPT revolutions. The detailed analysis of dislocation contrast factors in X-ray diffraction line profiles enables to determine the population of the different slip systems as a function of the imposed strain. The influence of microstructure and defect structure evolution on microhardness is discussed in detail.