Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear

Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa

Analysis of shear deformation scheme efficiency in plastic structure formation processes

The paper is devoted to the analysis of such an important factor as deformation behavior in the simple shear conditions.It is shown that non-monotonous character of material plastic flow exerts significant influence on the intensity of initial structure refinement. Induced non-monotonous character that ensures formation of equiaxed structural states plays an important role in the process

Microstructure and mechanical properties of AISi 304l austenitic stainless steel processed by various schedules of rolling

The paper studies various rolling schedules implemented at 500°С (incl. direct, reverse, and cross rolling) and their effect on the structure formation and mechanical properties in AISI 304L stainless steel samples. Both TEM and SEM research techniques were applied. An ultrafine grain-subgrain microstructure was found to be formed inside elongated original grains. Rolling-processed microstructural elements were close in their size with the minimum value observed after a reverse rolling (240 nm

Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear

Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa

Temperature and strain rate dependence of microstructural evolution and dynamic mechanical behavior in nanocrystalline Ti

The mechanical behavior of commercial purity titanium with a nanocrystalline (NC) grain size was investigated using split Hopkinson pressure bar tests at high strain rates and over a range of temperatures. The study was accompanied by detailed microstructural investigations before and after compression testing. The results show that rotary dynamic recrystallization operates during compressive deformation at strain rates of ~3000 and ~4500 s?1 at temperatures from 298 to 573 K but cells form at 673 K. The dynamic mechanical behavior of NC Ti shows a strong dependence on temperature and strain rate such that the flow stress and the strain hardening rate both increase with increasing strain and decreasing temperature. A constitutive equation is derived to relate the flow stress to the temperature, strain rate and true strain and to predict the yield strength and the peak stress of NC Ti subjected to dynamic deformation at elevated temperatures

Fundamentals of interface phenomena in advanced bulk nanoscale materials

The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materials 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 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 studied. Also enhanced grain boundary diffusivity is addressed. Structure recovery and dislocation emission from grain boundaries in nanocrystalline materials have been investigated by analytical methods and modeling

Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food : Outcome of the collaborative trial IMEP-41

Peer reviewedPublisher PD

Effect of temperature on the evolution of structure, crystallographic texture and the anisotropy of strength properties in the Ti grade 4 alloy during continuous ECAP

© 2015 Advanced Centr Co. Ltd. This paper presents the results of experimental studies on the evolution of structure, crystallographic texture and the anisotropy of strength properties in the volume of Ti Grade 4 billets subjected to continuous equal-channel angular pressing (ECAP). Continuous ECAP is performed at temperatures of 200° 400° and 450° with 1 to 8 passes, using route BC. The methods of X-ray diffraction analysis are employed to investigate the effect of processing regimes and strain degree during continuous ECAP on the structure of the material under study. As a result of computer modelling of the crystallograpic texture evolution, the regularities in the formation of preferred orientations and the anisotropy of strength properties are established, and the activity of various slip systems and twinning systems in titanium billets, depending on the number of ECAP passes, is evaluted. Estimation of the anisotropy of strength properties, based on building of yield contours, shows that an increase in the number of passes of continuous ECAP promotes the formation of a more isotropic structure. The obtained results allow to explain and predict the deformation behavior of nanostructured Ti Grade 4 with consideration of its microstructure and crystallographic texture parameters

Iso-osmotic regulation of nitrate accumulation in lettuce (Lactuca sativa L.)

Concerns about possible health hazards arising from human consumption of lettuce and other edible vegetable crops with high concentrations of nitrate have generated demands for a greater understanding of processes involved in its uptake and accumulation in order to devise more sustainable strategies for its control. This paper evaluates a proposed iso-osmotic mechanism for the regulation of nitrate accumulation in lettuce (Lactuca sativa L.) heads. This mechanism assumes that changes in the concentrations of nitrate and all other endogenous osmotica (including anions, cations and neutral solutes) are continually adjusted in tandem to minimise differences in osmotic potential of the shoot sap during growth, with these changes occurring independently of any variations in external water potential. The hypothesis was tested using data from six new experiments, each with a single unique treatment comprising a separate combination of light intensity, N source (nitrate with or without ammonium) and nitrate concentration carried out hydroponically in a glasshouse using a butterhead lettuce variety. Repeat measurements of plant weights and estimates of all of the main soluble constituents (nitrate, potassium, calcium, magnesium, organic anions, chloride, phosphate, sulphate and soluble carbohydrates) in the shoot sap were made at intervals from about 2 weeks after transplanting until commercial maturity, and the data used to calculate changes in average osmotic potential in the shoot. Results showed that nitrate concentrations in the sap increased when average light levels were reduced by between 30 and 49 % and (to a lesser extent) when nitrate was supplied at a supra-optimal concentration, and declined with partial replacement of nitrate by ammonium in the external nutrient supply. The associated changes in the proportions of other endogenous osmotica, in combination with the adjustment of shoot water content, maintained the total solute concentrations in shoot sap approximately constant and minimised differences in osmotic potential between treatments at each sampling date. There was, however, a gradual increase in osmotic potential (ie a decline in total solute concentration) over time largely caused by increases in shoot water content associated with the physiological and morphological development of the plants. Regression analysis using normalised data (to correct for these time trends) showed that the results were consistent with a 1:1 exchange between the concentrations of nitrate and the sum of all other endogenous osmotica throughout growth, providing evidence that an iso-osmotic mechanism (incorporating both concentration and volume regulation) was involved in controlling nitrate concentrations in the shoot