Mechanical characterization of construction materials is a fundamental step to enabling reliable design. Globally, many standards in the field of mechanical characterization have been developed. With improving FEM simulations and material models, the local properties and anisotropies become very interesting, as they can be implemented in FEM simulations. However, data on local properties should be provided based on so fan no-standard miniaturized specimens providing information for specific locations/orientation to feed material models. With specimens downsizing there are consequently many issues, such as geometrical similarity between standard and miniaturized specimens and probably the main one, the microstructure. As the miniaturized specimens for engineering applications should still be related to material behavior, some critical number of grains should be within the volume of the specimens gauge section in order to represent polycrystal behavior. This paper deals with the investigation of grain size influence on tensile behavior determined with the use on miniaturized tensile specimens with gauge section thickness of 0.5mm. Tensile tests are a very basic test in the field of mechanical properties characterization, and specimens downsizing can be seen in many papers nowadays, eg. (1-2). It has been proven that the performance of miniaturized tensile tests in comparison to standard ones is very good. In order to set the boundaries up to which it is possible to go regarding the specimens cross section and maintain comparability with standard sized specimens, the grain size influence is investigated here. Two steels with several different grains sizes are investigated here. Various grain sizes were obtained by heat treatment, resulting in a wide range of the grain sizes. Tensile tests of standard specimens and miniaturized ones are carried out on the investigated heats of steels for comparison. The results obtained here point out that very good performance of miniaturized tensile tests in terms of providing information on bulk material behavior can be achieved, even with very few grains over the specimen's thickness.

Determination of mechanical properties with the use of sub-sized specimens is a topic of high interest nowadays. The application of the sub-sized samples is quite wide for all cases where only limited amount of the experimental material is available such as evaluation of additively manufactured products properties, residual life of in-service components, properties determination of developed nanostructured materials, assessment of dilatometric samples used for thermal and thermo-mechanical treatment development, local properties of components, weld joints, etc. Concerning this large application field, it would be very useful to prepare a standard for small size samples, especially for most demanded material properties: tensile properties, notch impact transition temperature, fatigue properties, fracture toughness and creep. The current work is dealing with fracture toughness employing master curve and J-R curve approaches for fracture toughness parameters determination with the use mini specimens. The experimental material is reactor pressure vessel steel provided in the form of 2T-CT specimens. These specimens are tested and from the broken halves 1T-CT specimens are machined as well as full-size Charpy specimens, mini 0.16T-CTs and mini Charpy specimens. Results of fracture toughness tests achieved for different size specimens are subsequently compared and the size effect in assessed.

Nickel based super alloy MoNiCr was developed as the material with high corrosion and creep resistance against aggressive molten fluoride salt environment. This medium is used by Fluoride salt cooled High temperature Reactor (FHR) and Molten Salt Reactor (MSR) systems. The elements Mo, Cr and Fe are most important alloying elements accompanied by very low amount of Al + Ti. Necessity to prepare hot formed semi products such as sheets, bars, wires and tubes was the motivation for this new experimental program execution searching for suitable hot forming conditions. In the case of MoNiCr components forming, recrystallization is a crucial process allowing successful forming. Special attention was paid to this process after finding out, that this process is running very slowly or even not running at all, if inappropriate conditions are met. Proper temperature and strain rate range were determined and furthermore the influence of cold deformation on recrystallization progress was determined. It was found that cold deformation before hot forming as well as after hot forming can be successfully implemented into technological chain. Almost fully recrystallized microstructure can be achieved using synergy of both cold and hot deformation.

In this study, the relationship between the structure and properties of commercial purityaluminium (AW-1199) was investigated by applying constrained groove pressing (CGP) method.The refinement of the coarse grain aluminium microstructure to submicrocrystalline size by largeplastic strain at room temperature defined. The impact of various strains upon microstructurechanges is investigated using transmission electron microscopy (TEM) and electron back scatterdiffraction (EBSD). A mixture of subgrains produced by grains subdivision and polygonizedsubgrains formed locally due to dynamic recovery was found in the deformed aluminium. Thetensile properties and resulting hardness are related to microstructural evolution induced by CGP. Asubstantial impact of straining upon the increasing in tensile strength was observed after the firstpass. Further strain increase had an insignificant effect on tensile strength but was accompanied byductility loss. The post deformation annealing effect was then explored with aim to increase theductility. The results indicate that changes in strength and ductility may be related to formation of abimodal structure.

The present work, deals with grain refinement of medium carbon steel AISI 1045 (0,45 % C having different initial ferrite-pearlite microstructure resulted from thermal and thermomechanical (TM) treatment. The purpose of steel TM teatment was to refine ferrite phase and modify pearlite lamellae structure. The final grain refinement of steel structure was then accomplished during warm Equal Channel Angular Pressing (ECAP) deformation at 400 degrees C. Employment of this processing route, in dependence of the applied effective strain epsilon(ef), resulted in extensive deformation of ferrite grains and cementite lamellae fragmentation. Applying higher shear stress the mixed structure of subgrains and ultrafine grains was formed within ferrite grains, regardless the initial steel modification. In pearlite grains modification of cementite lamellae due to shearing, bending, twisting and breaking was found efficient. Processes of dynamic polygonization and recrysallization in deformed structure also contributed to formation of intensively deformed structure. Comparing the results course lamellae cementite spheroidization was then more efficient in prior TM treated steel. The tensile deformation results confirmed the strength the strength increase, deformation behaviour and strain hardening generally for different initial structural conditions of steel, showed diversity across deformed bars.

The present work, deals with grain refinement of medium carbon steel AISI 1045 (0.45% C), having different initial ferrite–pearlite microstructure resulted from thermal and thermomechanical treatment (TM). The purpose of TM steel processing was to refine ferrite and modify pearlite lamellae structure. The final grain refinement of steel structure was then accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. Employment of this processing route, in dependence of the applied effective strain ϵef, resulted in extensive deformation of ferrite grains and cementite lamellae fragmentation. When applying higher shear stress (ϵef = 4) the mixed structure of subgrains and ultrafine grains was formed within ferrite phase, regardless the initial steel structure morphology. In pearlite grains, modification of cementite lamellae due to shearing, bending, twisting, and breaking was found efficient as straining increased. Processes of dynamic polygonization and recrystallization in deformed structure also contributed to submicrocrystalline grains formation in deformed structure. Comparing results the course of lamellae cementite spheroidization was then more efficient in prior TM treated steel. The tensile deformation results confirmed the strength increase, however deformation behavior and strain hardening generally for different initial structural conditions of steel, showed diversity.

In this study ultrafine grain structure evolution during high pressure torsion (HPT) of commercial aluminium alloy AA6082 at increased temperature is presented. Two different initial structural states of the alloy were prepared by thermal treatment. The progress in structure refinement in dependence on the shear strain level strain was investigated by TEM of thin foils. The impact of different amount of strain (εef) introduced was analyzed with respect to the effect of increased temperature. The microhardness results measured across the deformed discs pointed out that some data scattering. The results of microstructure analyses showed that ultrafine grain (ufg) structure was already formed in deformed disc upon the first turn, regardless the initial structure of alloy, resulting from prior thermal treatment. The observed heterogeneity in ufg structure formation across the deformed disc was observed, supporting microhardness results scattering. By increasing the strain level (number of turns N-2,4,6), more effectively homogenized ufg structure was observed across the deformed discs. The effect of increased deformation temperature became evident and dynamic recrystalization modified locally ufg structure.. The retardation of new grains growth and higher thermal stability of ufg structure was observed, when two steps thermal treatment of alloy (quenching and ageing) was executed prior deformation. Strength measurements results yielded form tensile tests showed that the effect of structure strengthening was degraded by local recrystallization. The results of torque measurement versus the time showed that the torque required to deform the sample was increasing until the first turn and then kept stable or even decreased.

This paper gives a description of the project entitled "West-Bohemian Centre of Materials and Metallurgy - WBCMM". It details key aspects of the project and new strategies for collaboration between manufacturing companies and the research sector. Project activities carried out in the last year and newly adopted laboratory research methods and tests are recapitulated. Finally, the paper presents information on the equipment of the new metallurgical hall and on WBCMM research programmes that will be launched this year.

In this study, ultrafine grain structure evolution during high pressure torsion (HPT) of commercial aluminium alloy AA6082 at an elevated temperature is presented. Two different initial structural states of the alloy were prepared by thermal treatment. The dependence of the progress of microstructure refinement on shear strain was investigated by TEM observation of thin foils. The impact of various amounts of strain (epsilon(ef)) was analysed with respect to the increased temperature of deformation. Microhardness data measured across the deformed discs show scatter. Observation of microstructure revealed that an ultrafine grain (UFG) structure formed in the deformed disc as early as the end of the first turn, regardless of the initial structure of alloy resulting from the prior thermal treatment. The heterogeneity of UFG deformed structure in the deformed discs is consistent with the scatter in microhardness values. By increasing the strain level through adding turns (N = 2, 4, 6), the UFG structure was homogenized in the deformed discs. The effect of the increase in deformation temperature became more evident and dynamic recrystallization modified the UFG structure locally. In the specimens prepared by two-stage thermal treatment (quenching and ageing) prior to torsion deformation, the growth of new grains was inhibited and the UFG microstructure was more stable. Tensile strength values suggest that strengthening was partially relaxed by local recrystallization. Torque vs. time plots reveal that the torque required to deform the sample was increasing until the completion of the first turn and then remained stable or even decreased slightly.

The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain epsilon(ef) similar to 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 mu m and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400 degrees C. The microstructure development was analyzed in dependence of effective strain introduced (epsilon(ef) similar to 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.

The article focuses on the results from recent experimental of severe plastic deformation (SPD) of low carbon steel AISI 1010 and medium carbon steel AISI 1045 performed at increased temperatures. The grain refinement of ferrite respectively ferrite-pearlite structure is monitored and described. While LC steel was deformed by ECAP die with a channel angle phi = 90 degrees and by strain epsilon(ef) = 3. The ECAP severe deformation of MC steel was conducted with die channel angle of 120 degrees and epsilon(ef) = 2.6 - 4) and T-ECAP - 400 degrees C. The high straining in LC steel resulted in extensively elongated ferrite grains with dense dislocation network, and randomly recovered and polygonized structure was observed although. The small period of work hardening appeared at tensile deformation. On the other side, the warm ECAP deformation of MC steel in dependence of increased effective strain resulted in more progressive recovery process in deformed structure. In interior of the elongated ferrite grains the subgrain structure with dislocation network prevailed. As straining increases dynamic polygonization and recrystallization became active to form mixture of polygonized subgrain and submicrocrystalline grain structure. The straining and moderate ECAP temperature caused the cementite lamellae fragmentation and spheroidzation as number of passes increased. The tensile behaviour of the both steels was characterized by strength increase however the absence of strain hardening was found at low carbon steel. The favourable effect of ferrite-pearlite structure modification due straining was reason for extended work hardening period observed at MC steel.

In this study, the relationship between the structure and properties of commercial purity aluminium (A1199) was investigated by applying constrained groove pressing (CGP) method. The refinement of the coarse grain aluminium (Al) microstructure to submicrocrystalline size by large plastic strain at room temperature is defined. The impact of various strains upon microstructure changes is investigated using transmission electron microscopy (TEM) and electron back scatter diffraction (EBSD). The tensile properties and resulting hardness are related to fine microstructure evolution induced by CGP. A substantial straining upon the increase in tensile strength was observed after the first pass. Further strain increase had an insignificant effect on tensile strength and was accompanied by ductility loss. The post deformation annealing effect was then explored with aim to increase the ductility. The results indicate that changes in strength and ductility may be related to formation of a bimodal structure.

Using the high pressure torsion (HPT) deformation method the medium carbon steel (AISI 1045) was the experimental material used to conduct the deformation process. The torsion deformation experiment was performed at increased temperature of 400 °C. The influence of deformation processing parameters, resolved shear strain γ (number of turns N = 1–6) and applied pressure p (constant pressure of 7 GPa), was evaluated by microstructure analysis and mechanical properties. The strength behaviour was assessed by microhardness measurements across the disc to detect the positional hardening, by tensile tests and in situ measured torque. In situ measurement of torque during deformation allows characterizing the changes in mechanical properties due to the large shear deformation developed across the disc. To obtain absolute values of strength the ultimate tensile strength was measured in radial direction with respect to the deformed sample. From each deformed disc two sub-sized tensile test specimens with gauge length of 2.5 mm were machined. The tensile strength in samples increased markedly with the number of turns. The hardness measured at disc edge gradually increases as straining increases until it saturates after 2–3 turns. However, the hardness values at edge were different from those measured in disc centre and for applied straining no saturation was reached across the disc. The SEM and TEM investigations were carried out to analyze the fine microstructure evolution regarding the strain introduced. To follow the difference in strain distribution across the deformed disc the microstructure analysis was performed at edge and central site of the disc in order to evaluate the effect of the strain distribution. TEM investigation confirmed the increasing misorientation even in very small grains, the fragmentation and dissolution of the cementite lamellae, (diffuse cementite/ferrite boundaries), the alignment of the fragments to the shear plane with increasing deformation. Indistinct deformation of ferrite and preserved cementite lamellae morphology were found at the centre of the disc.

The aim was to compare two different ways of the physical simulation of the controlled rolling and cooling of the case-hardening steel 16MnCrS5. We used the results obtained by hot rolling in the laboratory mill TANDEM (VSB-TU Ostrava) and simulation of analogous modes of processing on the unique simulator of thermomechanical cycles (COMTES FHT a.s.), the principle of which is based on the alternating pressure and tensile deformation. The required forming temperatures were obtained by the resistive heating, the temperature was measured by thermocouples welded on the surface of the testing sample. The maximum speed of the piston is 500 mm s(-1). Two ways of the thermomechanical treatment were simulated - either the cooling in the free air from the finish rolling temperature was realized, or a complex mode including the accelerated water spray cooling to the coiling temperature was applied, combined with subsequent retarded cooling of the coil in the Garret coilers, installed in the continuous small section mill at Trinecke zelezarny a.s. The rolled down products with thickness 6.4 mm and the specimens with initial dimensions circle divide 6x11mm formed on the simulator were subjected to tensile tests and the metallographic evaluation of microstructural characteristics. The structure of specimens from the simulator featured a larger heterogeneity and a complicated transition area from the testing part to the clamping heads. This found its reflection also in the mechanical properties, which in the case of the analogous rolling showed a comparable yield point though, but substantially lower strength and - vice versa - higher elongation at the room temperature. These differences are caused to a great extent by the different shape and size of specimens for the tensile test (in the case of the cylindrical specimens formed on the simulator, the part of the specimen subsequently subjected to the tensile test had the diameter only 4 mm and length 4 mm).

The present work deals with grain refinement in low carbon steel (AISI 1010) by severe plastic deformation (SPD). The effect of structure modification was evaluated with respect to thermomechanical (TM) treatment of steel prior to SPD. The grain refinement was accomplished during warm angular channel pressing (ECAP) at 300°C. The evolution of microstructure during equal channel angular pressing (ECAP) was studied using SEM and TEM of thin foils. Ultrafine-grained structure development is described in relation to strainintroduced. At lower strain applied, the subgrain and/or polygonized structure was frequently found. Due to increased deformation temperature, the dynamic recovery contributed to structure refinement in both structural states. The amount of high angle boundaries increased with higher ECAP strain and was higher in TM-processed steel. There was only an indistinctive difference in structure refinement, considering different initial structures of the steel.The deformation behaviour of UFG steel in dependence on processing conditions was evaluated by a tensile test and correlated with structural characteristics.

The present work deals with grain refinement of medium carbon steel, having different initial microstructure, modified by either thermal and/or thermomechanical treatment (TM) prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain of 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 mu m and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400 degrees C. The microstructure development was analyzed in dependence of effective strain introduced (epsilon ef similar to 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. The straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The cementite lamellae spheroidization was more extensive in TM treated steel samples. The tensile behavior was characterized by strength increase for both structural steel states; however the work hardening behavior was modified in steel where preliminary TM treatment was introduced to modified coarse ferrite-pearlite structure.

Commercial low carbon steel AISI 1010 was subjected to Equal Angular Channel Pressing (ECAP) at different temperatures. The paper describes the refinement of the coarse grained ferrite microstructure to submicrocrystalline range by large plastic strain. The steel was deformed in an ECAP tool with a channel angle φ = 90°, at different temperature in the ranging between 150 – 300°C. The number of passes at each temperature was N = 3. Optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the formation of substructure and ultrafine grains in the deformed specimens. The TEM study reveals that at the lowest ECAP temperature of 150°C extensively elongated ferrite grains with dense dislocation network dominate in the structure. The randomly scattered polygonized subgrains have been observed. The activation of dynamic recovery process, even at the lowest temperature of equal channel pressing, contributed to the formation of individual polygonized grains. As the temperature of ECAP processing was increased the process of dynamic polygonization and recrystallization occurred more effectively and the submicrocrystalline structure was formed by sectioning of elongated ferrite grains. The formation of such predominant submicrocrystalline structure resulted in strength increase of the low carbon steel.