Degree Of Cold Deformation Research Articles

Hydrogen diffusivity, uptake and embrittlement of solution annealed and cold deformed austenitic stainless steel 1.4435 at hydrogen pressures up to 1000 bar and 200 °C

Austenitic stainless steel 1.4435, a candidate material for high-pressure tubing for hydrogen applications, was investigated in two different stages of cold deformation (0 and 27 %) regarding its hydrogen embrittlement tendency. The determination of effective diffusion coefficients revealed slightly increased diffusion kinetics at 60°C for the cold-reduced material (8.0 · 10−15 m²/s) compared to the solution annealed one (5.0 · 10−15 m²/s). High-pressure gaseous hydrogen charging shows no differences regarding the degree of cold deformation with a maximum hydrogen concentration of 112 wt.-ppm. Furthermore, a significant ductility loss expressed by the ratio of the reduction of area was observed.

Hydrogen resistance and trapping behaviour of a cold-drawn ferritic–pearlitic steel wire

Abstract The present work investigates the resistance of a progressively cold-drawn carbon steel wire against hydrogen embrittlement. In this study, analytical and numerical methods are used to determine the critical hydrogen content, the critical hydrogen ratio and the embrittlement indices of the different material conditions. The wire with the highest degree of cold deformation shows the highest critical hydrogen content and improved resistance against hydrogen embrittlement. At higher degrees of deformation, the material shows stronger hydrogen trapping, which improves in combination with a change in the lamellar spacing and orientation of the pearlite the resistance to hydrogen embrittlement.

Hydrogen embrittlement characteristics in cold-drawn high-strength stainless steel wires

Hydrogen uptake and embrittlement characteristics of a cold-drawn austenitic stainless steel wire were investigated. Slow strain rate testing and fracture surface analysis were applied to determine the hydrogen embrittlement resistance, providing an apparent decrease in resistance to hydrogen embrittlement for a 50% degree of cold deformation. The hydrogen content was assessed by thermal desorption and laser-induced breakdown spectroscopy establishing a correlation between the total absorbed hydrogen and the intensity of near-surface hydrogen. The sub-surface hydrogen content of the hot-rolled specimen was determined to be 791 wt.ppm.

Study on Cold Hardening and Recrystallization Temperature of Cu-Ni-Sn-P Alloy for Integrated Circuit Lead Frame

The work hardening curve of the Cu-Ni-Sn-P alloy for the integrated circuit lead frame was drawn by different degrees of cold deformation. The recrystallization temperature of the alloy was determined by testing the tensile strength, Vickers hardness, elongation, and electrical conductivity of the samples annealed at different temperatures and microstructure observation. The results show that the Cu-Ni-Sn-P alloy had obvious work hardening characteristics after being deformed by cold rolling; the tensile strength of the alloy showed a trend of first increasing and then tending to be stable with the increase of the working rate, while the elongation and electrical conductivity showed the opposite changing law. At the same annealing time, with the increase of annealing temperature, the tensile strength of Cu-Ni-Sn-P alloy decreased slowly first and then sharply, and finally tended to be stable. To effectively reduce energy consumption and shorten the production cycle, the reasonable recrystallization annealing system of Cu-Ni-Sn-P alloy after 60% deformation is determined to be 440°C×4h.

A novel route to improve the fatigue properties of aviation M50 steel via tailoring the bainite content and cold deformation

The microstructure, mechanical and fatigue properties of M50 steel by combining austempering processing with cold deformation have been investigated. The results show that the introduction of bainite can effectively refine the multiphase microstructure. When the bainite content is 10.5%, the finest microstructure and the best combination between strength and toughness can be obtained. It is also found that 20% cold deformation leads to a slight improvement of tensile strength and impact toughness, while the mechanical properties deteriorates significantly under larger cold deformation. It is concluded that the mechanical properties can be improved by tailoring the bainite content at about 10% and cold deformation degree at 20%. For the tailored specimen, the specific life of rolling contact fatigue is 114.1% longer than that of traditional martensitic quenched specimen. The slope parameter of Weibull distribution function also shows an increase from 1.8267 to 2.2992, reflecting the more stable of RCF life. There are fewer microcracks in the subsurface of peeling pits, which should be attributed to the higher toughness and finer carbides. Additionally, owing to the higher density of grain/phase boundaries, the tailored specimen with a lower hardness shows better resistance to plastic deformation under the wear trace. This finding provides a novel route to improve the RCF properties of M50 steel via strictly tailoring the bainite content and cold deformation degree.

Study of a complex of physical, crystallographic and mechanical properties of aluminum foil for electrolytic capacitors

The results of studies of the complex of physical, crystallographic and mechanical properties of aluminum foil for low-voltage and high-voltage electrolytic capacitors made of high-purity aluminum (99.99% Al) are presented. A comparative analysis of technological schemes for the production of foil for lowvoltage and high-voltage applications is given, the main differences in the schemes are shown, and the results are presented for the physical parameter: the value of specific capacitance, crystallographic characteristics (structure and predominant texture), mechanical properties (tensile strength and relative elongation). Low-voltage foil after electrochemical etching has a fine etching relief, which can cause the danger of its smoothing after the next operation of the electronic processing of molding — the creation of an oxide film of the dielectric. The required surface topography can be achieved at high total degrees of cold deformation, amounting to 98.8%, without intermediate annealing, obtaining a structure that is fibrous along the rolling direction with a predominant deformation texture {011} and pole density according to the results obtained (5.2). On the contrary, high-voltage foil after electrochemical etching has a rougher relief, and here the risk of surface smoothing after the molding operation is minimal, since the dielectric oxide film being formed is actually superimposed and duplicated along the trajectory of the resulting relief. The latter can be achieved by using a foil after recrystallization (intermediate) and final annealing to obtain an average grain size of about 72 microns, a predominantly near-cubic texture of the {420} foil, and a pole density of 2.4 obtained results. At the same time, high values of specific capacitance can be observed in the studied range: at forming voltages of 30 and 450 V, the value of specific capacitance is 1750 and 29 μF/dm2 for low-voltage and high-voltage foils, respectively.

Determining the hardening curve and mechanical properties of rolled strips made of aluminium alloy AD33 with known chemical composition

The chemical composition of the material was studied by the opticalemission spectral method, which allowed us to determine the specific composition of aluminum alloy, which corresponds to the AD33 brand according to the Russian standard 4794-19. There was some experimental rolling of strips with a size of 3×25×190 mm with a compression of 10, 20 and 30% followed by testing the samples for rupture in order to determine the mechanical properties of the deformed rolled products. Based on the obtained data, the yield curve and the dependence of the time resistance σв and the relative elongation δ have been created to show the degree of deformation of the alloy. As the result, the regularities of changes in the strength and plastic characteristics of the degree of cold deformation of the AD33 aluminum alloy strips of known chemical composition have been established. The experiment shows that the time resistance σв and the yield strength increase with increasing compression with different intensities: σв increases monotonically almost linearly; increases intensively from 70 to 160 MPa at compression from 0 to 15%, and then slowly increases to 173.5 MPa at ε = 30%. The plasticity index — δ decreases from 29.35 to 11.2% according to the parabolic law of the second degree. Regression equations are obtained that allow us to calculate the main indicators of mechanical properties when rolling strips of aluminum alloy AD33 of known chemical composition. The adequacy of the obtained equations, confirmed by high correlation coefficients (R2 > 0,9), allows us to recommend them for the calculation of powwer indicators of rolling and design in automated design systems (CAD) of rational modes of deformation of aluminum alloy strips AD33.

Coinciding significance of the crystallographic orientation and nanostructuring on the biocompatibility of TZNT-Ag1.5 alloy deformed by the cold rolling process.

In this study, the simultaneous significance of the crystallographic texture and nanostructuring on the cytocompatibility of as-cast (Ti55 Zr25 Nb10 Ta10 )98.5 -Ag1.5 alloy (at. %, TZNT-Ag1.5 ), subjected to cold rolling up to 90% reduction, along with the changes of Young's modulus and hardness under cold rolling were investigated. For this purpose, the as-cast and cold-rolled TZNT-Ag1.5 alloy test specimens were analyzed by XRD, TEM, HRTEM, SEM, contact angle, nanoindentation, and OM techniques. Moreover, to evaluate the effect of severe cold deformation on the biocompatibility, MG-63 osteoblastic cell was cultured on the surface of 90% cold-rolled and as-cast test specimens of TZNT-Ag1.5 alloy. The results showed that severe cold deformation was led to fast grain refinement of grains of the as-cast TZNT-Ag1.5 alloy in the range of 50-100 nm. In addition to the nanostructuring, upon severe cold deformation, the <gamma>-fiber (<111>// normal direction) texture was formed and after 90% reduction, the (111)<1 > γ-fiber component was strengthened. The micro-hardness and reduced Young's modulus are 235 ± 5.29, 246 ± 1.73, 271 ± 4.0, and 283 ± 6.25 (HV); and 73.725 ± 1.70, 83.98 ± 5.10, 81.26 ± 6.55, and 88.66 ± 7.16 (GPa) for TZNT-Ag1.5 (as-cast), TZNT-Ag1.5 (20%CR), TZNT-Ag1.5 (50%CR), and TZNT-Ag1.5 (90%CR) test specimens, respectively. Further, with increasing the cold deformation degree, the dislocation density of TZNT-Ag1.5 alloy increased as this parameter is 2.79 × 1015 (m-2 ) for the 90%CR test specimen. On the other hand, the values of the contact angle for the 90%CR test specimen (46.2 ± 3.5°) exhibit a higher hydrophilic and wettable surface as compared to the other studied test specimens. After 5 days of incubation, osteoblastic cells on the surface of the 90% cold-rolled TZNT-Ag1.5 test specimens revealed significant differences in cell proliferation and differentiation as compared to the as-cast alloy test specimens and/or CP-Ti. Finally, because the maximum orientation intensities were generally <3, it was deduced that grain refinement rather than the crystallographic texture plays a significant role in improving the surface biocompatibility of the new TZNT-Ag1.5 alloy.

INFLUENCE OF PLASTIC DEFORMATION CARBON STEEL ON THE PROCESS OF BURNING ELECTRIC ARC

During a study of the combustion process of a direct polarity electric arc, a directly proportional dependence of the electric current value on the degree of cold plastic deformation of carbon steel used as an electrode was found. To calculate the value of the electric current during arc burning, in the indicated ratio, it was proposed to replace the surface tension force of the liquid metal with the surface tension of ferrite of plastically deformed carbon steel. Calculation of the ferrite’s surface tension value on the deformation degree of the steel under study through the size of the coherent scattering regions was used to explain the observed dependence of the electric current during arc burning. From the analysis of the considered correlation ratios, it was found that with an increase in the cold deformation degree, the refinement of the coherent scattering regions results in the ferrite’s surface tension increase and consequently, to an increase in the electric current during arc burning. Comparative analysis of the obtained results of calculating the value of electric current during arc burning through the surface tension of ferrite of cold-deformed carbon steel showed a fairly good coincidence with experimental data. The differences did not exceed 9%.

Stress-Strain Behavior – Deformation Degree Relationship Investigation of Alloy CrNi60WTi

The article presents the results of a research of the dependence of the mechanical properties of the CrNi60WTi alloy on the degree of cold deformation. As part of the study, five samples were taken from a pipe with an outer diameter of 89.0 mm and a wall thickness of 11.0 mm. The samples were cold-deformed to varying degrees and static tensile tests were performed on an SSI MTSInsight tensile testing machine. Based on the test results, the dependences of the mechanical properties on the degree of cold deformation were calculated.

Single-Step Heat Treatment for the Restoration of Mechanical Properties of Cold-Strained Mining Support Steel 31Mn4

The steel 31Mn4+QT630 is used frequently for mining support arches. The supports are cold strained, first during service, and again by re-rolling prior to reinstallation, which results in strain hardening and a loss of ductility. Consequently, many of the rerolled arch-segments are not suitable for reinstallation because their mechanical properties are inadequate. The objective of this work was to assess the feasibility of restoration of the required mechanical properties by means of a cost-efficient single step heat treatment. Specimens were cold deformed to different degrees in the range 0 % to 45 % to establish the relation between the degree of cold deformation and the hardness. Differently strain hardened specimens were subjected to subcritical annealing at temperatures 450 °C to 700 °C in the duration 0.5 h to 8 h to determine a suitable time-temperature combinations. Microstructures and mechanical properties were investigated of as-received, cold strained and recrystallized specimens. Tests performed were optical microscopy, scanning electron microscopy, tensile tests, hardness measurements and Charpy impact tests. Elongation at break of the as-received material was below the requirements of the applicable standard, and its microstructure contained significant fractions of pre-eutectoid ferrite and pearlite. Upon cold straining, hardness increased by approximately 2 HV per 1 % of strain. After one-hour recrystallization at 600 °C to 620 °C, the microstructure consisted of a ferritic matrix containing evenly dispersed globular carbide particles. The original ductility was restored, while the elongation, yield strength, and hardness were higher than in the as-received condition. These results confirmed that it is feasible to restore the original mechanical properties of heavily strained profiles with an adequate single-step heat treatment. Furthermore, they indicated that it should be possible to recover the required properties of inhomogeneously strained material with the same set of well optimized heat treatment parameters. Consequently, it should be possible to increase the reuse rate and to decrease the costs for new support arches significantly.

Corrosion performance of various deformed surfaces of implant steel for coronary stent applications: Effect of protein concentration

This work was done to systematically elucidate the corrosion behavior of austenitic stainless steel subjected to various degree of cold deformation (10 %, 20 % & 30 %). The experiments were performed in phosphate buffer saline (PBS) solution having different concentrations of bovine serum albumin (0.2, 0.5, 1.0, 2.0, 4.0 g L−1). Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) analysis were performed to obtain the corrosion parameters. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface morphologies and chemical compositions of the surface films. Contact angle analysis was also used to detect the hydrophilic character of sample surfaces. The BSA had a considerable effect of inhibition on the corrosion of SSs in annealed as well as in deformed state due to its adsorption on surface of steel. For annealed samples, at 4.0 g L−1BSA concentration, the corrosion resistance was drastically decreased but interestingly not for sample with more than 10 % deformation and the concentration effect of BSA is also not very significant after 0.5 g L-1 for deformed surfaces. The breakdown potential for 30 % deformed sample is quite higher in presence of BSA even at 4.0 g L−1 while it is lowest for annealed samples in the same condition. The variation in contact angle with deformation is very less after adsorption of BSA. On the basis of the obtained results, mechanism aspect for corrosion of steel in presence of protein is also deliberated.

Effect of single wall carbon nanotubes on strength properties of aluminum composite produced by spark plasma sintering and extrusion

Aluminum composite material reinforced by single walled carbon nanotubes (SWCNT) was made by spark plasma sintering (SPS) followed by extrusion directly on spark plasma sintering machine. For the first time it was possible to carry out not only sintering by SPS method, but also extrusion of aluminum-based composites with SWCNT additives directly on the Labox 1575. The effect of the degree of cold deformation and annealing on the strength of aluminum containing SWCNT is studied. It was found that there is an optimal degree of cold deformation, providing maximum growth of strength of aluminum composites reinforced by SWCNT. It was shown that composites extruded at elevated temperature had more significant strength decrease after annealing. Nevertheless, these composites have the highest strength values. The increase in ultimate tensile strength and yield strength of aluminum due to SWCNT additives was 47% and 158%, respectively.

Work softening behavior of Cu–Cr–Ti–Si alloy during cold deformation

Work hardening is a common method of strengthening copper-based alloys. However, softening behavior is observed in Cu–Cr–Ti–Si alloy during cold rolling processes. Cold deformation greater than 85% can induce softening behavior. We used an electron backscatter diffraction system, X-ray diffraction, and transmission electron microscopy to analyze the microstructure of alloy samples subjected to different degrees of cold deformation. A greater proportion of high-angle grain boundaries, a lower dislocation density, and certain dislocation configurations indicated that the recovery takes place during heavy cold deformation leading to softening phenomenon.

Effect of Prior Cold Deformation on the Stability of Retained Austenite in GCr15 Bearing Steel

In this work, the effect of prior cold deformation on the stability of retained austenite in GCr15 bearing steel was investigated after quenching and tempering treatment. The thermal stability was evaluated by calculating thermal activation energy for decomposition of retained austenite using differential scanning calorimeter. The mechanical stability was investigated according to the strain-induced martensitic transformation behavior of retained austenite under the standard compression testing. It is found that the prior cold deformation not only accelerates the carbide dissolution during the austenitization process but also contributes to the carbon partitioning in the tempering stage due to the higher density of phase boundaries, which results in the improvement of the thermal stability of retained austenite. Due to the enhanced carbide dissolution, the higher carbon content in the prior austenite will intensify the isotropic strain of martensitic transformation. As a consequence, the film-like retained austenite is likely to form under a higher hydrostatic pressure and thus shows a higher mechanical stability. Additionally, it is noteworthy that the benefits of the prior cold deformation to the stability of retained austenite would be saturated when the cold deformation degree is larger than 40%.

The effect of inhomogeneous microstructures on strength and fatigue properties of an Al-Cu-Li thick plate

The inhomogeneity of the microstructure of an Al-Cu-Li thick plate in the thickness direction results in inhomogeneity in the tensile property and fatigue crack propagation (FCP) rate. The grain size gradually increases from the surface layer to the central layer. The contents of low-angle grain boundaries (LAGBs) were characterized by an electron backscattered diffraction (EBSD) technique, and the LAGBs, which act as nucleation sites, induced a greater number of T1 precipitates in the central layer. In the surface layer, the random texture resulted from the greater recrystallization degree due to the high degree of cold deformation during the rolling process. The 1/8 layer contained a rotated cube texture, which is a typical shear texture. A strong β fiber rolling texture was found in the central layer, including S, brass and copper texture components, because the adequate recovery during hot rolling decreased the recrystallization driving force. Both the yield strength (YS) and ultimate tensile strength (UTS) gradually increased from the surface layer to the central layer, i.e., UTS from 479.7 MPa to 546.0 MPa, YS from 455.9 MPa to 514.0 MPa. The inhomogeneity of the tensile properties was primarily caused by the different textures, LAGB content and T1 precipitate density. However, the surface layer had a distinctively lower FCP rate than the central layer. The disparity in the FCP rate between the surface layer and the central layer could be attributed to the roughness and plasticity, which are related to the LAGBs, the T1 precipitates and the grain size.

EFFECT OF AGING TREATMENT PARAMETERS ON MICROSTRUCTURE AND PROPERTIES OF Cu-Ni-Si ALLOY

In this paper, effect of cold pre-deformation and sequent aging time and temperature on microstructure and properties of Cu-2.8Ni-1.0Si alloy are reported. The results shown that, hardness and electrical conductivity of alloy increase with increasing cold deformation degree after quenching and subsequent aging. With undeformed specimens after quenching, hardness and electrical conductivity of alloy reach maximum values with subsequent aging at 425 and 475 oC, respectively. Alloy attains maximum hardness of 255 HV5 with aging at 425 oC for 4.5 hours, while maximum electrical conductivity of 38.5 %IACS with aging at 475 oC for 8 hours. In the case of deformed specimens after quenching and subsequent aging, this rule is still preserved. Especially, at 70 % cold pre-deformation degree, alloy attains the maximum hardness of 274.3 HV5 with aging at 425 oC for 3.5 h, while maximum electrical conductivity reaches 42.4 % IACS with aging at 475 oC for 6 h.

Microstructure, texture evolution and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn biomedical beta titanium alloy

Ti-32.5Nb-6.8Zr-2.7Sn (TNZS, wt%) alloy was produced by using vacuum arc melting method, followed by solution treatment and cold rolling with the area reductions of 50% and 90%. The effects of cold rolling on the microstructure, texture evolution and mechanical properties of the experimental alloy were investigated by optical microscopy, X-ray diffraction, transmission electron microscopy and universal material testing machine. The results showed that the grains of the alloy were elongated along rolling direction and stress-induced α″ martensite was not detected in the deformed samples. The plastic deformation mechanisms of the alloy were related to {112}〈111〉 type deformation twinning and dislocation slipping. Meanwhile, the transition from γ-fiber texture to α-fiber texture took place during cold rolling and a dominant {001}〈110〉α−fiber texture was obtained after 90% cold deformation. With the increase of cold deformation degree, the strength increased owing to the increase of microstrain, dislocation density and grain refinement, and the elastic modulus decreased owing to the increase of dislocation density as well as an enhanced intensity of {001}〈110〉α−fiber texture and a weakened intensity of {111}〈112〉γ−fiber texture. The 90% cold rolled alloy exhibited a great potential to become a new candidate for biomedical applications, since it possesses low elastic modulus (47.1GPa), moderate strength (883MPa) and high elastic admissible strain (1.87%), which are superior than those of Ti-6Al-4V alloy.

Effects of cold deformation on electrochemical corrosion behaviors of 304 stainless steel

PurposeThe purpose of this study was to investigate the effects of deformation-induced martensite on electrochemical corrosion behaviors of 304 austenitic stainless steel in a simulated primary water environment of a pressurized water reactor nuclear power plant with boric acid and lithium hydroxide contaminated with chloride by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott–Schotty curves and X-ray photoelectron spectroscopy (XPS).Design/methodology/approachThe effects of deformation-induced martensite transformation on electrochemical corrosion behaviors of 304 austenitic stainless steel was investigated in a simulated primary water environment of a pressurized water reactor nuclear power plant with boric acid and lithium hydroxide contaminated with 0.1 M Cl− by potentiodynamic polarization, EIS, Mott–Schotty curves and XPS in this paper.FindingsThe results revealed that the martensitic phase contents increased with the level of cold deformation. The general corrosion current density and the corrosion potential increased and decreased, respectively, with the increase of cold deformation degree. However, the pitting potential decreased as the cold deformation increased up to 20 per cent, then a slight increase was observed at 35 per cent cold working. It was found from Mott–Schottky curves and XPS analysis that as the cold deformation degree increased from 0 to 35 per cent, the doping concentrations of the oxide films increased; however, the film thickness decreased, which indicates that both density and integrity of the films are degraded significantly as the deformation degree increases, and this ultimately contributes to the significant increment of the general corrosion rate and reduction of the pitting corrosion resistance.Originality/valueThe effects of deformation-induced martensite transformation on electrochemical corrosion behaviors of 304 austenitic stainless steel was investigated in a simulated primary water environment of a pressurized water reactor nuclear power plant with boric acid and lithium hydroxide contaminated with 0.1 M Cl− by potentiodynamic polarization, EIS, Mott–Schotty curves and XPS in this paper.

Фильтровальные перегородки из спеченных металлических сеток для встроенных фильтров авиационных гидросистем

Results of theoretical and experimental researches related to cold deformation degree influence when rolling on strength&#x0D; and hydraulic characteristics of metal gauzes used for production of built-in filters’ filtering walls have been presented.&#x0D; An analytical dependence of gauze’s permeation coefficient on the gauze’s reduction ratio and relative lengthening when&#x0D; rolling has been received based on ideal porous body’s capillary model. Theoretical research results have been compared&#x0D; with the experimental data obtained at filtration of compressed air and mineral oil through samples of gauzes with various&#x0D; degree of cold deformation. Experimental dependences of gauzes’ relative lengthening and strength limit on their cold&#x0D; deformation degree have been presented. Results of visual researches of deformed gauzes’ surface condition have been&#x0D; presented. A dependence of contact spots’ square at gauzes’ surfaces on reduction ratio has been received. The analysis of&#x0D; contact spots’ influence on hydraulic characteristics of the multilayered mesh material used for filtering walls production&#x0D; has been carried out. Results of experimental studies of gauzes’ hydraulic characteristics have been processed in the form&#x0D; of dimensionless dependence of hydraulic resistance coefficient on filtered environment stream’s Reynolds number.