Subsequent Aging Research Articles

Increasing strength and electrical conductivity of Cu-0.77%Cr-0.86%Hf alloy by rotary swaging and subsequent aging

Increasing strength and electrical conductivity of Cu-0.77%Cr-0.86%Hf alloy by rotary swaging and subsequent aging

EFFECT OF STRUCTURAL-PHASE STATE ON THE DEFORMATION BEHAVIOR AND MECHANICAL PROPERTIES OF NEAR β TITANIUM ALLOY VT22 IN THE TEMPERATURE RANGE 293-823 K

This paper investigates the effect of thermomechanical treatments, including deformation by radial shear rolling or severe plastic deformation by abc pressing with subsequent aging at 773 K, on the structural-phase state, deformation behavior and mechanical properties of commercial near β titanium alloy VT22 (Ti-5Al-5Mo-5V-1Cr-1Fe). The structure of the alloy after radial shear rolling and subsequent aging consists of transformed β grains with a lamellar α + β structure and primary α-phase particles. Severe plastic deformation of the alloy followed by aging causes the formation of a grain-subgrain α + β structure with an average characteristic size of 0.23 µm. It is found that after the thermomechanical treatments, the strength characteristics of the alloy at room temperature increase by ~40% compared to the as-received alloy. The alloy after radial shear rolling and aging retains a 40-20% higher strength in the temperature range of 293-823 K. The strength of the alloy after severe plastic deformation and aging becomes lower than that of the as-received alloy already at a temperature of 773 K. Analysis of creep parameters at 743 K shows that the creep deformation of the alloy in the state after radial shear rolling and aging occurs by the motion of dislocations (glide + climb). The creep deformation of the alloy in the state after severe plastic deformation and subsequent aging is largely contributed to by grain boundary sliding.

MECHANICAL PROPERTIES AND FRACTURE OF ULTRAFINE-GRAINED NEAR β TITANIUM ALLOY UNDER THREE-POINT BENDING

Comparative studies are conducted on the structure and mechanical properties of the ultrafine-grained Ti-5Al-5V-5Mo-1Cr-1Fe alloy obtained by abc pressing and radial shear rolling with subsequent aging. It is shown that the ultrafine-grained structure formed by these methods provides increased strength properties both in tension and in three-point bending compared to the initial coarse-grained state. At the same time, the alloy obtained by abc pressing demonstrates a higher resistance to fracture during three-point bending compared to the alloy obtained by radial shear rolling + aging due to its enhanced ductility. This also determines the ductile pattern of fracture of the ultrafine-grained alloy obtained by abc pressing during three-point bending in contrast to brittle-ductile fracture of the alloy obtained by radial shear rolling + aging.

Effect of thermomechanical training on recovery stress of Fe-based shape memory alloy

This research explores the impact of thermomechanical treatment on the recovery stress induced by the shape memory effect in an Fe-based shape memory alloy with the composition of Fe-17Mn-5Si-10Cr-4Ni-1(V,C) wt.%. Fe-based shape memory alloys have gained considerable attention for their potential applications in vibration control, energy dissipation, and structural strengthening or re-centering within the construction industry. To evaluate the recovery stress behaviour of this Fe-based shape memory alloy, specimens underwent a two-step aging heat treatment process, involving initial aging at 600 °C for 20 hours, followed by subsequent aging at 680 °C for 8 hours. Then heat-treated samples subjected to a cyclic thermomechanical treatment, involving a combination of deformation up to 2% and heating at 200 °C for 30 min in each cycle. The microstructure and mechanical properties were assessed using techniques such as scanning electron microscopy, as well as tensile tests. The results revealed that the thermomechanical treatment had a notable impact on the microstructure and mechanical properties of the Fe-based shape memory alloy. It resulted in an enhancement of the shape memory effect and recovery stress. These improvements were associated with an increase in the martensitic phase fraction. Additionally, the presence of VC precipitates in the treated samples contributed to the enhancement of the shape memory effect.

Акустические свойства мартенситно-стареющей стали XM-12 после энергетических воздействий

The study of the acoustic properties of maraging steels operated under various energy force and temperature actions is a critical task, since it is the method of acoustic structuroscopy that provides the most reliable connection with the structure, stress-strain state and mechanical properties of steels. The paper is devoted to research of the acoustic properties of the 15-5 PH maraging steel samples under various types of heat treatment under the conditions of mechanical tensile and cyclic loads. Samples of the 15-5 PH maraging steel were studied in three structural states: solid solution annealing and subsequent aging at 470 and 565 °C; during tensile tests; during cyclic tension-compression loading. The research used a unique scientific installation “Information-measuring complex for investigation of acoustic properties of materials and products”. It implements the acoustic mirror-shadow multiple reflections method using electromagnetic-acoustic and piezoelectric transducers based on polyvinylidene fluoride film to excite and receive waves and allows determining the velocity of wave propagation with an error of no more than 2 m/s. The acoustic (wave velocity, elastic moduli, electromagnetic-acoustical (EMA) transformation coefficients, acoustic anisotropy coefficients, acoustoelastic coupling coefficients) and electromagnetic (coercive force and electrical conductivity) characteristics of the samples were examined. The samples were studied in the initial state (before loading); stepwise in the process of tensile loads and subsequent unloading; after tensile tests; during cyclic tension-compression loading. It was revealed that the following acoustic parameters of 15-5 PH steel samples are the greatest structural sensitivity to mechanical tensile load and cyclic loading: transverse wave velocity, Poisson’s ratio, double EMA-transformation coefficient, and acoustic anisotropy coefficient.

Association between iron deficiency anemia and sleep duration in the first year of life.

The aim of this study was to investigate the association between iron deficiency anemia and sleep duration in the first year of life. A total of 123 infants were investigated, with sleep being evaluated at 3, 6, and 12 months of age and anemia at birth and 6 months. The cutoff points for anemia and short sleep duration were hemoglobin <11 g/dL (at birth and/or 6 months) and <10 h (at 3, 6, and 12 months), respectively. The comparison of the average sleep time between infants with and without anemia was performed using the Student's t-test, and logistic regression models were also used to verify differences in the sleep duration (short/not short) between the groups. Linear regression analyses were conducted to determine the association between sleep duration and hemoglobin values. The analyses were adjusted for potential confounders. Children with anemia were more likely to be short sleepers [odds ratio (95% confidence interval (CI)): 4.02 (1.02-15.76); p≤0.05], and for each unit increase in hemoglobin values, the sleep duration increased by 16.2 min [β (95%CI): 0.27 (0.00-0.55); p≤0.05), regardless of family income, maternal schooling, gender, and body mass index at birth. Our results suggest that iron deficiency anemia is associated with short sleep duration in the first year of life and indicate the need for longitudinal investigations, with longer follow-up, to verify the impact of anemia on sleep duration at subsequent ages.

What we talk about when we talk about spinal cord aging

Spinal cord-associated disorders are common in the elderly population; however, the mechanisms underlying spinal aging remain elusive. In a recent Nature paper, Sun etal. systemically analyzed aged spines in nonhuman primates and identified a new cluster of CHIT1-positive microglia that drives motor neuron senescence and subsequent spine aging.

Analyzing the Reported Prevalence of Heart Disease among United States Adults: Trends from the National Center for Health Statistics Database

Objective This study aims to comprehensively analyze and elucidate the reported prevalence of heart disease among United States adults, utilizing data extracted from the National Center for Health Statistics database from 1999 to 2019. Methods We conducted a thorough analysis of the National Center for Health Statistics database to examine demographic and socioeconomic variables, such as age, gender, race, education, poverty level, geographic region, and metropolitan status, influencing heart disease prevalence among United States adults. The outcomes were concisely summarized using aggregate data from 1999-2019, delineating prevalence trends across all participants throughout these years. One-way Analysis of Variance was utilized for statistical analyses, assessing variations in heart disease prevalence across diverse demographic and socioeconomic categories. Results The study reported notable trends in age-specific prevalence, revealing distinct patterns across different age groups. The age-adjusted average reported heart disease prevalence for individuals aged 18 and over from 1999 to 2019 was 5.9%,. Within the 18-44 age group, prevalence started at 1.0% and increased notably across subsequent age brackets: 45-54 (4.3%), 55-64 (9.9%), 65-74 (16.8%), and 75 and older (24.4%). Adult men consistently had a higher prevalence (7.6%) than women (4.5%). Prevalence varied among racial groups, with the highest in American Indian or Alaska Native-only individuals (12.4%). Socioeconomic variables illustrated a robust association between lower educational attainment, poverty, and increased heart disease prevalence. Geographic and metropolitan status analyses unveiled significant regional and residential disparities in reported heart disease prevalence. Education-level analysis revealed a higher prevalence for lower education (9.1%) and a lower prevalence for higher education (6.1%). Significant differences were observed in each category (p &lt; 0.001). Conclusion This study highlights epidemiological patterns and reports heart disease prevalence, stressing the urgency for targeted interventions and preventative measures. Results underscore the importance of addressing temporal patterns, demographic inequalities, and geographic disparities through strategic public health efforts.

EFFECT OF ASYMMETRIC ROLLING ON THE STRUCTURE AND PROPERTIES OF CU-CR-ZR ALLOYS

Asymmetric rolling is a high-tech method based on the principles of severe plastic deformation (SPD). In the present paper, it is shown that Cu-0.8Cr-0.1Zr alloy is highly strengthened during asymmetric rolling due to structure refinement to an ultrafine-grained state. For example, in only one pass, at the accumulated strain 0.94 ± 0.20, the strength increases from 265 to 425 MPa. During the deformation process, the structure becomes refined, with the average size of fragments reaching 235 ± 90 nm. Structure heterogeneity is also observed in the cross section of a sample, which is associated with different rotation speeds of the rolls. The shape of grains in the central zone of samples corresponds to the state after conventional symmetric rolling. However, in the zone adjacent to the roll rotating at a higher speed, mechanical texture of grains is similar to that after shear. Subsequent aging of Cu-0.8Cr-0.1Zr alloy at 450°C makes it possible to achieve the ultimate strength 560 MPa and electrical conductivity 82% IACS, which exceeds the characteristics of the strengthened steel by 10-15%. The analysis of contributions to strengthening during asymmetric rolling reveals that the main contribution comes from refinement of the grain structure to an ultrafine-grained state, which amounts to 58%. The fractions of the dislocation and dispersion contributions comprise 15 and 20%, respectively. Compared to conventional rolling, as well as other deformation methods that provide the same level of accumulated strain and strengthening in one cycle, such as equal channel angular pressing-conform, asymmetric rolling is the most promising due to its simpler process scheme.

Іmprovement of performance characteristics and increase of productivity in the production of rolled-welded steel pipes

Thin-sheet cold-rolled 08kp steel is widely used in the production of two-layer copper-plated rolled-soldered tubes by complex processes of cold deformation with metal extraction and subsequent soldering. Problem. For high-quality molding, steel must have high technological plasticity, which is ensured by recrystallization annealing of rolls of rolled steel in periodic garden hood furnaces. It is impossible to obtain a sheet with increased properties, to correct the lack of sheet blanks due to poor-quality deformation, to prevent the subsequent aging of steel over time by processing in hood furnaces. During the manufacture of tubes, annealing of blanks, forming and soldering are carried out in different workshops of the enterprise, which is definitely not economical. Goal. The aim of the work is to improve both the technological and service characteristics of 08kp steel, intended for the manufacture of rolled soldered tubes, and to ensure the possibility of combining all processes of their production in a single line. To achieve the goal, it is necessary to develop an optimal mode of high-speed weakening heat treatment of riveted rolled steel and to study the possibility of replacing soldering in a muffle furnace with high-speed induction soldering. Methodology. The cold-rolled strip was subjected to continuous annealing at 700 °C and subsequent aging at 400 °C for 2 minutes using contact heating (~100 °C/s) in an argon atmosphere. Inductive soldering rolled up copper tubes were made at 1150ºС and duration of heating up to 30 seconds. After soldering, the tube was cooled in a thermostat with argon to a temperature of 900 – 950ºС and subjected to tempering at 600 – 650ºС lasting up to 2 s to prevent deformation aging. Result. Two-stage high-speed heat treatment (recrystallization tempering and aging) guarantees 08kp steel a high level of properties for defect-free forming of small-diameter tubes. High-speed induction soldering allows you to combine all processes in one current line. Practical value. The unification of all tube manufacturing processes in one current line ensures the improvement of their quality, surface cleanliness, absence of aging, reduction of defects and increase of production productivity, reduction of transport costs of manual labor and the number of working personnel. Tubes manufactured using the developed technology passed 100% incoming inspection under production conditions.

Legacy effects of earthworms on soil microbial abundance, diversity, and community dynamics

The earthworm species Lumbricus terrestris L. feeds on plant litter mixed with surrounding soil. Here, we analyzed with a mesocosm approach and soil incubations how that activity and subsequent ageing of casts (feces) affects the abundance and diversity of the soil microbiome. Earthworms were fed either with straw of sainfoin (SA, Onobrychis viciifolia; C/N ratio 22) or winter wheat (WW, Triticum aestivum, C/N ratio 101). The gut transit increased the abundances of bacteria and fungi, but reduced archaea. As indicated at the DNA and RNA level, main beneficiaries of the facilitated access to nutrients were members of Bacteroidota, especially Flavobacteriales with an estimated generation time of only 2 h. While Alphaproteobacteria were reduced, Gammaproteobacteria also increased in abundance and activity. SA was more nutritious for L. terrestris, and supported a higher bacterial abundance, probably because more N was available for growth and denitrification. During cast ageing, prokaryotic community compositions became increasingly similar to bulk soil communities. However, they remained distinguishable even after 168 d, suggesting that effects can last beyond a vegetation period. Dry-wet conditions preserved these differences better than continuous moisture. During ageing, more complex prokaryotic networks were detected with WW and dry-wet conditions. Thus, N and water limitations appeared to enhance cooperation rather than competition between the prokaryotes. Overall, this study demonstrates that earthworm soil interactions strongly affect the diversity and temporal dynamics of the soil microbiome. Legacy effects of earthworm activities should thus be kept in mind when investigating the environmental variation of soil microbiomes.

Fast synthesis of mechanically robust methylsilsesquioxane aerogels: Process parameters optimization based on condensation reactions

Ambient pressure drying is a mainstream alternative to the supercritical drying process for synthesizing aerogels due to its low cost and high safety, but the problems of time-consuming and low mechanical properties of the synthesized aerogels need to be solved. This work tailored the skeleton of methylsilsesquioxane aerogels by ammonia concentration (cNH3·H2O) and revealed their microstructure evolution mechanism affected by the condensation reactions of methyltrimethoxysilane hydrolysates in the subsequent aging and drying process. The effects of process parameters, including the cNH3·H2O, aging temperature and time, drying temperature and time on the gelation time, macroscopic morphologies, microstructures, and compression properties of as-synthesized methylsilsesquioxane aerogels were investigated. A cNH3·H2O of 4.0 mol/L endowed the methylsilsesquioxane aerogels with a compression strength of 0.171 MPa and a maximum compression strain of 59.5 %. The optimal aging conditions were at 50 °C for 3 h which increased the compression strength and maximum compression strain of as-synthesized aerogels to 0.201 MPa, and 66.2 %, respectively. The synthesis time of methylsilsesquioxane aerogels was reduced to 6.5 h through an optimized step drying process, while further increasing their compression strength and maximum compression strain to 0.359 MPa and 73.5 %, respectively. The process parameters optimization method enables the facile synthesis of methylsilsesquioxane aerogels with mechanically robust texture, providing a theoretical basis for developing next-generation scalable production technologies of aerogels.

Regulating microstructure and improving precipitation hardening response of fine-grained Mg-RE-Ag hot-extruded alloy by extreme short-time heat treatment

The difficulty in exerting beneficial effects of fine grains, high number density nano-precipitates as well as weakened texture simultaneously is currently the bottleneck limiting the development of high performance (high strength, high plasticity, and isotropic) age-hardenable Mg-RE alloys. The key difficulty is that the generation of excessive dynamic precipitates is always accompanied by the formation of fully dynamic recrystallized ultrafine grains during thermal deformation, causing a significant depletion of solutes within the entire matrix and finally seriously weakening the subsequent aging nano-precipitation. In this work, the process of extreme short-time (2 min) heat treatment (ESHT) followed by peak aging treatment is applied to an ultrafine-grained weak-textured Mg-RE-Ag as-extruded alloy with numerous dynamic precipitates. The precipitation hardening response is dramatically increased (ΔHV = 37.2 HV) and the yield strength is increased by nearly 50 MPa. This is attributed to the fact that concentration of main solutes in matrix is greatly increased within only 2 min of heat treatment promoting the precipitation of nano-precipitates (prismatic β′ and basal γ′′) in the absence of excessive grain growth. The large difference between the initial and equilibrium solute concentrations, the extremely short distance required for solute diffusion within sub-microscale grains, and the effective pinning of grain boundaries by excess dynamic precipitates are responsible for the unusual microevolution during the ESHT. In addition, the formation of precipitation-free zones (PFZs) is attributed to ‘uphill’ diffusion during aging, and novel γ′′-PFZs and β′-PRZs are found. The ESHT followed by peak aging treatment provides a new way to simultaneously exert the beneficial effects of fine grains and high number density nano-precipitates.

Monitoring the State of Health (SOH) of Green Batteries (GreenBat)

Here we focus on the study of state of health monitoring of secondary batteries with advanced “green” formulations. European recycle map on battery energy storage plans to replace positive electrodes consisting of cobalt (Co) and fluorinated (F) graphite-based negative electrodes constituents with environmentally sustainable alternatives. Recently, "green formulations" was validated; in particular, recent trends suggest the use of electrodes based on silicon (Si), Co-free manganites (LiMnO2) aqueous soluble binders and fluorine-free electrolytes [1]. Our aims are to describe the health and the degradation of the cells with electrochemical techniques and to describe the chemical and morphological changes occurring during the battery cycling, through spectroscopies (Raman and IR) operating in parallel with impedance analysis. These experimental data will be integrated together in a multiblock dataset, which will constitute the basis for chemometric processing. The purpose of this chemometric modelling is to correlate SOH evolution to the chemical and physical state of the battery [1]. Here we illustrate the analysis of SOH of two different pouch cells formulation constituted by LTO (Lithium-Titanate) as anode, LFP (Lithium-Iron-Phosphate) as cathode and the LP30 electrolyte (EC:DMC 1:1 and LiPF6 1M); the second formulation is constituted by a thin film layer of commercial Li metal (purity of 99.7%) as anode, LFP as cathode and an ethers based formulation as electrolyte. After formation cycles (CC-CV), the cells have been submitted to aging tests. The different operating conditions are chosen with an Experimental Design (ED) and supported by a PCA analysis. The PCA analysis it was used to choose the operating parameters for the subsequent aging experiments. Is illustrated also the analysis of SOH of a coin cell formulation consisted by a LRLO (Lithium Rich Layer Oxide) as anode, commercial Li metal layer as cathode and LP30 additive with a ionic liquid (IL) as electrolyte. Turning to the chemometric modelling, as a starting point we verified the ability of PLS regression applied to the voltage profiles during charge cycles to estimate the SOH of a benchmark dataset by Lin et al. [1] References [1] M. Lin,D. Wu, Journal of Power Sources, 2022, 518, 230774. Figure 1

The effect of modified atmosphere packaging at an early postmortem stage on lamb meat quality during subsequent aging.

This study explores the influence of modified atmosphere packaging (MAP) on fresh lamb meat quality with respect to gas concentration, rigor state, and post-mortem aging time. A comparison was done for the quality characteristics of lamb Longissimus thoracis lumborum chops that had been packaged separately in air, 75%O2 +25%CO2 MAP or 50%O2 +50%CO2 MAP at 1, 6, and 24h post-mortem and then stored for 6, 12, 24, 72, and 144h post-mortem, and the quality of lamb chops had been evaluated at each post-mortem period separately. Chops packaged at 1 and 6h post-mortem in MAP had reduced pH decline, less purge loss, and enhanced redness at early post-mortem storage times. Lamb color stability was evidently greater in 75%O2 +25%CO2 MAP than in 50%O2 +50%CO2 MAP during the early storage period when a* and R630/R580 were taken into account. Shear force values were lowest in lambs packaged at 1h post-mortem with 75%O2 +25%CO2 MAP at 12h post-mortem and then increased until 72h post-mortem, suggesting that rigor has been delayed by such a high O2 MAP. Thus, fresh lamb quality was maintained most effectively when packaged at 1h post-mortem in 75%O2 +25%CO2 MAP for consumption at 12h post-mortem. The exact mechanisms and optimization of MAP based on Chinese retail conditions should be considered in future studies. PRACTICAL APPLICATION: In this study, three slaughter patterns in the meat industry involving boning immediately after dressing (hot-boning) and chilling for a short period (warm-boning) or overnight (cold-boning) are considered, as well as the behavior of non-immediate consumption after purchase. Modified atmosphere packaging provides an effective preservation of early post-mortem muscles with enhanced color stability, water holding capacity, and texture during refrigerated storage. This could provide new insights into how to process lamb muscles in the early post-mortem period to improve and stabilize lamb quality.

RECEIPT OF CHEMOTHERAPY AND COGNITIVE DECLINE AMONG MEDICARE BENEFICIARIES IN THE US HEALTH AND RETIREMENT STUDY

Abstract Research on cancer and cognitive aging outcomes has been inconsistent, with clinic-based studies showing short-term cognitive declines after chemotherapy, and population-based epidemiological studies observing inverse associations between most cancers and subsequent cognitive aging. We aimed to determine the effect of chemotherapy on cognitive decline and mortality among Medicare beneficiaries in the population-based US Health and Retirement Study (HRS). Using data from HRS-Medicare linked participants ≥65, we identified 858 incident breast, prostate, and kidney cancer diagnoses from 2000 to 2016. Cognitive function was measured using the modified telephone interview for cognitive status (range 0 to 27). Cancer treatment (chemotherapy only, other treatments, and no treatment) was obtained from Medicare claims. We used joint modeling to simultaneously model the association between cancer treatment with cognition decline and mortality. Of 858 participants, 38.7% had breast cancer, 52% had prostate cancer, and 11% had kidney cancer. The mean age at diagnosis was 72.8 years (SD=7.62). 31.7% (n=272) received chemotherapy only, 39.5% (n=339) received other treatment, and 28.8% (n=247) received no treatment. In pooled analyses, receipt of chemotherapy (vs. no treatment) was not significantly associated with cognitive decline (β: 0.08; 95% CI: -0.59, 0.76) but was significantly associated with mortality (HR: 1.39; 95% CI: 1.04, 1.88). In joint modeling, the overall hazard ratio for the receipt of chemotherapy (vs. no treatment) was 1.38 (95% CI: 1.02, 1.88). We found that receipt of chemotherapy was associated with an increased hazard of mortality, but not cognitive decline, compared to those who received no treatment.

Natural aging and vacancy trapping in Al-6xxx

Undesirable natural aging (NA) in Al-6xxx delays subsequent artificial aging (AA) but the size, composition, and evolution of clustering are challenging to measure. Here, atomistic details of early-stage clustering in Al–1%Mg–0.6%Si during NA are studied computationally using a chemically-accurate neural-network potential. Feasible growth paths for the preferred beta '' precipitates identify: dominant clusters differing from beta '' motifs; spontaneous vacancy-interstitial formation creating 14–18 solute atom beta ''-like motifs; and lower-energy clusters requiring chemical re-arrangement to form beta '' nuclei. Quasi-on-lattice kinetic Monte Carlo simulations reveal that 8–14 solute atom clusters form within 1000 s but that growth slows considerably due to vacancy trapping inside clusters, with trapping energies of 0.3-0.5 eV. These findings rationalize why cluster growth and alloy hardness saturate during NA, confirm the concept of “vacancy prisons”, and suggest why clusters must be dissolved during AA before formation of beta ''. This atomistic understanding of NA may enable design of strategies to mitigate negative effects of NA.Graphical abstractEnergy and RMS vacancy displacement vs simulation time for three different kMC simulations of Al matrix containing Mg (green) and Si atoms(orange), and 1 vacancy (pink). Geometries extracted from the third trajectory at four different times show solute clustering and vacancy trapping.

DISORDERS OF THE FATTY ACID SPECTRUM OF ERYTHROCYTES AND BLOOD PLASMA OF ADOLESCENTS WITH RECURRENT CEPHALGIA ASSOCIATED WITH HYPERTENSION. APPROACHES TO CORRECTION

The spectrum of fatty acids (FA) in erythrocytes and blood plasma reflects the characteristics of lipid metabolism in diseases of vascular origin, including cephalalgia associated with arterial hypertension (AH). Timely diagnosis and correction of violations of this spectrum is important for the prevention of diseases of the cardiovascular and nervous system in subsequent age periods of life. Objective. To study the characteristics of the FA spectrum of erythrocyte membranes and blood plasma in adolescents with recurrent cephalalgia associated with AH. Material and methods. The composition of FA of erythrocytes and blood plasma was studied in 51 adolescents aged 12–18 years with recurrent cephalgia associated with AH and without AH. Determination of the FA composition of erythrocytes and blood plasma was carried out by gas-liquid chromatography-mass spectrometry with preliminary lipid extraction according to the Folch method. The analysis of FA methyl esters was carried out on a gas chromatograph with a GCD Plus mass spectrometric detector (Hewlett-Packard, USA). Results. The features of the structural redistribution of individual FA in adolescents with cephalgia and AH in the form of a predominance of saturated and monoenic FA in erythrocytes with a simultaneous decrease in their content in blood plasma, as well as a tendency to a decrease in the concentration of polyunsaturated FA in erythrocytes and their increase in plasma. Conclusion. Early detection and timely correction of disorders of the FA spectrum of erythrocyte membranes and blood plasma is necessary, starting from childhood and adolescence, in order to subsequently reduce the risk of developing diseases of the cardiovascular and nervous system associated with these disorders.

Структурно-фазові характеристики та механічні властивості TWIP-сталі Fe-24Mn-11Al-1,4C

TWIP steels belong to a number of modern innovative structural materials that combine a high level of mechanical characteristics and low density, which brings their specific strength closer to the level of titanium alloys. Such steels usually do not contain deficient components and they are suitable for wide commercial industrial production. The most high-strength alloys include around 20-30 % Mn (wt.), around 10 % (wt.) Al and 1% (wt.) C. Such chemical composition brings them closer to the three-phase region, in which austenite, ferrite and k-carbides can simultaneously exist. According to this, it is possible to change mechanical characteristics of such alloys in a wide range only by heat treatment. Although in practice the best results are shown by a combination of deformation and heat treatment. The Manuscript presents a study of changes in the structural and phase characteristics and mechanical properties of the Fe-24Mn-11Al-1,4C alloy, prepared by electroslag melting, in its initial state, after deformation and annealing, and after deformation with subsequent hardening and aging. A fractographic analysis of the studied samples destruction places was also carried out. It is shown that the original sample obtained by electroslag remelting has the highest plasticity and the lowest strength, which is explained by combination of largest alloying of austenite and as-cast microstructure. The deformed and annealed sample is characterized by a pronounced fine-grained structure in which carbides are separated along the grain boundaries. Such a sample exhibits a strength greater than 1.1 GPa and the lowest ductility of 4.26 %. The deformed sample after quenching and aging has a similar structure, but the carbide inclusions are much finer, and the alloying rate of austenite is higher than the previous one. Such a sample shows the highest strength of more than 1.2 GPa and plasticity of 8.6 %. Keywords: TWIP-steels, casting, deformation and heat treatment, structural and phase characteristics, fractography, mechanical properties.

Microstructure and mechanical properties of a modified 316 austenitic stainless steel alloy manufactured by laser powder bed fusion

A 316 austenitic stainless-steel alloy, with modified alloy composition, manufactured by laser powder bed fusion (L-PBF) has been investigated. The modification of the alloy composition included addition of niobium (Nb), tungsten (W) and copper (Cu), together with a reduction in the amount of molybdenum (Mo) and an increased amount of carbon (C). To find suitable process parameters, a parameter study by varying laser power, hatch distance and scan speed was performed, centered on typical parameters used for normal 316 L. As-built material from a selected parameter configuration was then subjected to different stress relief annealing heat treatments and ageing heat treatments. The effectiveness of the stress annealing was ranked using a deformation-based method. Microstructural characterization, hardness and room temperature tensile testing were done to evaluate the effect of stress relief and aging heat treatments.It was found that a higher volumetric energy was needed to build dense material, about ∼50 % higher compared to the volumetric energy input for normal 316 L. A subsequent aging heat treatment at 725 °C for 3 h increased the strength and hardness of the material. A reinforcement of the cellular microstructure by precipitation of carbides in between the cells is believed to be the main reason for this. To completely alleviate the residual stresses it was necessary to carry out a stress relief annealing process at 950 °C, which resulted in a removal of the cellular structure and a lower strength material.