Effect Of Equal Channel Angular Pressing Research Articles

Study of biocompatibility and antitumor cytotoxic activity <i>in vitro</i> of Zn – 1 %Mg and Zn – 1 %Mg – 0.1 %Ca alloys strengthened by equal angular pressing

Introduction. The biological activity of potential biodegradable zinc-based alloys that are promising for oncoorthopedics was studied in this work. The alloys were processed by equal-channel angular pressing, which made it possible to increase their strength due to microstructure refinement and the ability to provide the functionality of osteosynthesis, fixed due to the metal structure developed on their basis.Aim. Investigation of effect of equal-channel angular pressing (ECAP) treatment on strength, ductility, degradation rate, biocompatibility in vitro and cytotoxicity against SKOV-3 tumor cells of the Zn – 1 %Mg and Zn – 1 %Mg – 0.1 %Ca alloys.Materials and methods. The Zn – 1 %Mg and Zn – 1 %Mg – 0.1 %Ca alloys in the initial state and after ECAP were used as objects of study, and blood cells of CBA mice were used as model systems. To assess the hemolytic activity, the samples were incubated with red blood cells for 4 and 24 hours at 37 °C, assessing the relative increase in the level of extracellular hemoglobin compared to the intact control. The cytotoxicity of the alloys was assessed by the change in the level of extracellular lactate dehydrogenase (LDH) activity after 24 hours of incubation with mononuclear white blood cells. The study of antitumor cytotoxic activity was carried out on human ovarian cancer cells of the SKOV-3 line in vitro, assessing their survival after 48 hours of incubation with alloy samples using the LDH test.Results. As a result of the studies, it was concluded that the studied alloys after ECAP treatment retained their biocompatibility, since there were no signs of hemolysis and cytotoxicity with respect to blood cells. However, contact with samples of all studied alloys in vitro induced a significant inhibition of the metabolic activity of the ovarian cancer cell culture in comparison with the control. Incubation with alloys samples leads to a decrease in cellular activity by an average of 49 % and 59 % for Zn – 1 %Mg and Zn – 1 %Mg – 0.1 %Ca alloys, respectively. The addition of calcium to the composition of the alloy Zn – 1 %Mg contributed to the growth of antitumor cytotoxic activity.Conclusion. Thus, based on the results of assessing the hemolytic activity and cytotoxicity of the samples, we can conclude that the studied alloys are biocompatible. It was also found that Zn – 1 %Mg and Zn – 1 %Mg – 0.1 %Ca alloys had a pronounced cytotoxic effect on SKOV-3 tumor cells. The obtained data indicate the prospects for the development of a new type of medical devices based on the studied alloys, promising, in particular, for oncoorthopedics: a metal structure developed on their basis can ensure the strength of osteosynthesis, reduce the risk of local recurrence of oncological disease and does not require a second operation to remove the device.

EFFECT OF EQUAL CHANNEL ANGULAR PRESSING AND SUBSEQUENT AGING ON THE STRUCTURE AND MECHANICAL PROPERTIES OF Al-Mg2Si ALLOYS WITH TRANSITION METAL ADDITIVES

The effect of equal-channel angular pressing (ECAP) at a temperature of 150°C and subsequent aging on the structure and strength characteristics of Al-Mg2Si alloys alloyed with Sc and combined additives (Sc + Zr) and (Sc + Hf) has been studied. An analysis of the dependences of hardness and electrical resistivity on time and temperature revealed the same nature of the decomposition of a supersaturated solid solution of alloys with additives (Sc + Zr) and (Sc + Hf), and also made it possible to obtain optimal aging conditions for these alloys. The microstructure of the alloys and the precipitation of secondary phases were carefully studied using scanning (SEM) and transmission electron microscopy (TEM). In alloys after ECAP and aging, an increase in both strength and ductility was revealed due to the compensation of aging processes by recovery processes associated with the rearrangement of the dislocation structure.

Effect of Equal-Channel Angular Pressing and Subsequent Aging on the Structure and Mechanical Properties of Al–Mg2Si Alloys with Transition Metal Additions

Effect of Equal-Channel Angular Pressing and Subsequent Aging on the Structure and Mechanical Properties of Al–Mg2Si Alloys with Transition Metal Additions

Effect of Plastic Deformation on the Structure and Mechanical Properties of the Zn-4Ag-1Cu Zinc Alloy.

It is known that zinc biodegradable alloys are a promising material for producing biomedical implants for orthopedics and vascular stents. Among them, the Zn-Ag-Cu zinc alloy is of special interest due to the antibacterial and antimicrobial properties of Ag and Cu. To improve the mechanical properties of the Zn-4Ag-1Cu zinc alloy, the effect of equal-channel angular pressing (ECAP) on the microstructure and strength has been investigated. The ECAP conditions for the Zn-4Ag-1Cu alloy were chosen by modeling in the Deform 3 D program (temperature and strain rate). The microstructure was analyzed using transmission electron microscopy, scanning electron microscopy and X-ray diffraction analysis. The study of strength was carried out by measuring the microhardness and tensile tests of small samples with a gauge dimension of 0.8 × 1 × 4 mm3. The microstructure after ECAP was characterized by equiaxed grains ranging in a size from 1.5 µm to 4 µm with particles in a size from 200 nm to 1 µm uniformly distributed along the boundaries. The ECAP samples showed a high strength of 348 MPa and good ductility of up to 30%, demonstrating their great potential as promising materials for producing medical stents.

The effect of thermal and strain-induced aging on the mechanical behavior of room temperature ECAP processing of WE43 magnesium alloy

The WE43 magnesium alloy, in case of improved toughness, can be an appealing material for biomedical applications. The effects of equal-channel angular pressing (ECAP) and post-deformation aging (PDA) on the mechanical behavior of the WE43 alloy were investigated in this study. ECAP of WE43 magnesium alloy at room temperature is extremely challenging because of the insufficient number of slip systems. An optimized core–sheath configuration is proposed, which applies fully compressive stress on the WE43 alloy as the core, resulting in ECAP of the WE43 alloy at room temperature. Unprecedented strain-induced precipitation of both Mg41Nd5 and Mg24Y5 was observed owing to stored mechanical energy and temperature raise in the adiabatic shear bands during ECAP at room temperature. Moreover, the formation of oriented needle-like Mg3(Y, Nd) precipitates and partial recrystallization simultaneously increased the strength to 410 MPa and the strain to fracture to 11.4% after PDA. A combination of bimodal grain size distribution and a high volume fraction of precipitates increased the toughness to 38.96 MJ/m3 after ECAP and PDA.

Effect of ECAP processing on distribution of second phase particles, hardness and electrical conductivity of Cu−0.81Cr−0.07Zr alloy

The effect of equal-channel angular pressing (ECAP) processing at room temperature and 300 °C on the distribution of the second phase particles and its influence on hardness and electrical conductivity of the commercial Cu−0.81Cr−0.07Zr alloy were investigated. Microstructural characterization indicated that the area fraction of coarse Cr-rich particles decreased after ECAP processing. This reduction was attributed to the Cr dissolution induced by plastic deformation. The electrical conductivity of the alloy decreased by 12% after 4 ECAP passes at room temperature due to the increase of electrons scattering caused by higher Cr content in solid solution and higher density of defects in the matrix. These results were supported by the reduction of the Cu lattice parameter and by the exothermic reactions, during differential scanning calorimetry (DSC) analysis, observed only in the samples subjected to ECAP processing. Aging heat treatment after ECAP processing promoted an additional hardening effect and the complete recuperation of the electrical conductivity, caused by the re-precipitation of the partially dissolved particles. The better combination of hardness (191 HV) and electrical conductivity (83.5%(IACS)) was obtained after 4 ECAP passes at room temperature and subsequent aging at 380 °C for 1 h.

Exploring the size effect in scaling up ECAP using the theory of similarity

The size effect of equal-channel angular pressing (ECAP) is investigated systematically, by examining the similarity of geometrical dimensions, mechanical parameters and thermal behaviors. The strain and strain rate distribution, microstructure and mechanical property evolution upon scaling up were characterized experimentally, followed by finite element simulations and theoretical analyses of thermal behavior. Steady and consistent microstructure recovery and mechanical properties softening observed in the eight-pass ECAP processed ultrafine-grained (UFG) copper upon scaling-up, demonstrate a significant size effect. The billet temperature profile rises upon scaling-up in simulation that accounts for the observed size effect. Theoretical analyses show that neither the heat conduction within the billet, nor the heat exchange between the billet and its surroundings could maintain similarity upon scaling. In other words, the size effect in ECAP is inherently rooted in the laws of thermal physics. Plunger velocity scaling down was proposed as an effective strategy to control the temperature rise and size effect upon scaling up. The fundamental discoveries uncovered by present work will benefit the scaling of ECAP for commercialization. And the frame of similarity applied to the examination of the ECAP process is believed to be also applicable to the scaling of other thermal mechanical processing.

Kinetics of phase precipitation in Al–Mg–Si alloys subjected to equal-channel angular pressing during subsequent heating

Effects of equal-channel angular pressing (ECAP) with subsequent aging on the microstructure and phase transformation of Al–Mg2Si alloys with combined (Sc + Zr) and (Sc + Hf) additions were studied. The microstructure processed by ECAP and the precipitation of phases of Al–Mg2Si alloys were thoroughly examined by transmission electron microscopy (TEM). An analysis of the precipitation and determination of the temperatures of these precipitations in Al–Mg2Si alloys after ECAP was carried out by DSC. It has been revealed that transition metals added to Al–Mg2Si alloys do not change the character of decomposition of the solid solution but shift the precipitation temperatures of the β'', β' and β phases to lower temperatures compared to the quenched state. Recovery processes have been revealed in the temperature range 200–600 °C based on the changes in hardness and electrical resistivity of Al–Mg2Si alloys with additions of transition metals (Sc + Zr) and (Sc + Hf) and without them after ECAP.

Effect of Quasi-Continuous Equal-Channel Angular Pressing on Structure and Properties of Ti-Ni Shape Memory Alloys

The effect of equal-channel angular pressing (ECAP) in quasi-continuous mode on the structure formation and mechanical and functional properties of a near-equiatomic Ti-Ni shape memory alloy (SMA) was studied in this work. ECAP with channel intersection angles of 110° and 120° was carried out at a temperature of 350-450 °C for 2-7 passes. Optimum deformation temperatures of ECAP in quasi-continuous mode are determined as 400 °C for ECAP with a channel intersection angle of 120° and 450 °C for 110°. ECAP with a channel intersection angle of 110° at a temperature of 450 °C yields high values of strength (yield stress σy = 1,090 MPa, ultimate tensile strength σв = 1,150 MPa) and functional (maximum value of completely recoverable strain of 7.5% after ECAP and 8.4% after the addition of post-deformation annealing (PDA) at 400 °C for 1 h) characteristics. With the increase in the deformation temperature of quasi-continuous ECAP with a channel intersection angle of 110° from 350 to 450 °C, structure-morphological transformation in Ti-Ni SMA occurs. The shape of structural elements (grains and subgrains) changes from elongated to equiaxed; the size of the structural elements increases from less than 100 nm to 100-250 nm.

Effect of equal channel angular pressing on microstructure and mechanical properties of thermally-homogenized Al–Mg2Si composites

The effect of equal-channel angular pressing (ECAP) on the microstructure, hardness, shear, and tensile properties of thermally-homogenized Al-xMg2Si (x = 10, 15, and 20 wt %) composites was studied. According to the microstructural characterization results, increasing ECAP passes progressively reduced the size of primary Mg2Si (Mg2SiP) and eutectic Mg2Si (Mg2SiE) particles, and improved their distribution within the matrix. These microstructural changes significantly improved the mechanical properties of the composites. For instance, after the final pass of ECAP, the shear yield strength (SYS) of composites containing 10, 15 and 20 Mg2Si increased by 89, 86 and 64%, while their tensile yield strength (TYS) increased by 174, 149 and 182%, respectively. A linear correlation between the tensile and shear strengths was also observed which is in agreement with the previous studies as well as Tresca and von Mises criteria.

The effect of equal-channel angular pressing (ECAP) on the properties of graphene reinforced aluminium matrix composites

In the present study, graphene nanosheets were synthesised by liquid phase exfoliation process, and the obtained graphene was reinforced in the rates of 0.1, 0.2, 0.3 and 0.6 wt.%. After the composites were characterised, they were exposed to Equal Channel Angular Pressing (ECAP) process. While 0.1 wt.% and 0.2 wt.% graphene reinforced composite samples successfully completed the ECAP process, 0.1 wt.% and 0.2 wt.% graphene reinforced composite samples were broken during the ECAP process. Electrical, thermal, and mechanical properties of the composite increased with the increased amount of graphene. The mechanical properties of ECAP-processed samples showed significant increases compared to non-ECAP processed samples. To figure out the effect of the ECAP process, moulds with different channel angles were used, the ECAP temperature was changed, and different passes were performed and the angles of 120° and 90° were used. ECAP-processed samples in both mould angles showed similar mechanical properties. With the increasing ECAP temperature, the mechanical properties of the sample decreased, but its electrical conductivity increased. As the number of passes increased, mechanical properties increased and crack formation in material increased. In addition, it was not possible to successfully remove the matrix composites containing more than 0.3 wt.% graphene from the ECAP process. Especially in the sample containing 0.6 wt.% graphene, brittle fractures were seen during the ECAP process and the sample was divided into many parts. The results showed that the composite responded better to the ECAP process when low amounts of graphene were reinforced in the al matrix. Significant improvements were observed in the properties of these composites after the ECAP process. In this study, the properties of composites with and without ECAP process were extensively investigated. The results were compared in detail with the previous studies. The graphene was produced using a simple method and it was reinforced with the Al matrix with the easiest possible method.

Analysis of the effect of equal-channel angular pressing on the strength and electrical conductivity of low-alloyed alloys of the Cu-Cr-Zr system

The effect of equal-channel angular pressing (ECAP) on the strength and electrical conductivity of low-alloyed Cu-Cr-Zr alloys to identify conditions for the formation of states with high strength and electrical conductivity is considered. The increase in the content of alloying elements does not increase the strength of the alloys in the initial quenched state. After ECAP, their strength is increased by dislocations. It is shown that after ECAP of quenched samples, their specific resistances remain almost unchanged due to the increase in the length of the grain boundaries, the volume fraction of small particles of secondary phases and the segregation of alloying atoms from the matrix.

The effect of transition metals on the structure and hardening of Al-Mg-Si alloys after cold plastic deformation

The effects of equal-channel angular pressing (ECAP) and rotary swaging (RS) on the change in strength properties during aging at 170 ° C of Al-Mg-Si alloys doped with Sc, Zr and Hf additions was studied. The methods of measuring hardness, electrical resistivity, testing mechanical properties, light and transmission electron microscopy were used. The higher hardening effect compared to the initial state was found in the alloys after ECAP than after RS, whereas the strength properties (tensile strength and yield strength) were higher for alloys subjected to RS than ECAP. Al-Mg-Si alloys with the combined additives of scandium with zirconium and scandium with hafnium showed practically the same values of hardness and strength properties at tensile testing during aging. The reason is in the identical nature of the decomposition of the supersaturated solid solution. It is determined by the sequence of precipitation of the strengthening phase Mg2Si and (Sc1-x, Zrx) Al3 and (Sc1-x, Hfx) Al3 dispersoids which impede the movement of dislocations both in alloys after deformation and after aging.

Effect of equal-channel angular pressing (ECAP) and current density of cathodic hydrogen charging on hydrogen trapping in the low-alloy steel

Effect of equal-channel angular pressing (ECAP) and current density of cathodic hydrogen charging on hydrogen trapping in the low-alloy steel

Effect of cold plastic deformation and subsequent aging on the strength properties of Al-Mg2Si alloys with combined (Sc + Zr) and (Sc + Hf) additions

Effects of equal-channel angular pressing (ECAP) and rotary swaging (RS) with subsequent aging on the strength properties of Al-Mg2Si alloys with (Sc + Zr) and (Sc + Hf) additions were studied. The microstructure of deformed alloys was examined by optical and transmission electron microscopy (TEM). Mechanical properties were characterized by hardness measurements and tensile testing. It was found that the strength properties of Al-Mg2Si alloys were remarkably improved due to the structure refinement during cold deformation and the acceleration of the kinetics precipitation of the βʹ and βʹʹ phases during aging of deformed alloys. It is found an accelerated decomposition of the supersaturated aluminum-based solid solution in the presence of hafnium. Nearly the same values of hardness and tensile strength of Al-Mg2Si alloys with transition metals additions have been accounted for the more intense decomposition of the solid solution with hafnium has compensated by a larger amount of hardening phases (βʹʹ and βʹ) in alloys with zirconium. For all alloys the highest hardness was achieved after cold deformation and remained nearly the same after 2 h of aging.

The Effect of Equal-Channel Angular Pressing on the Microstructure, the Mechanical and Corrosion Properties and the Anti-Tumor Activity of Magnesium Alloyed with Silver.

The effect of equal-channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, corrosion resistance and cytotoxicity of two magnesium-silver alloys, Mg-2.0%Ag and Mg-4.0%Ag, was studied. Their average grain size was found to be reduced to 3.2 ± 1.4 μm and 2.8 ± 1.3 μm, respectively. Despite the substantial grain refinement, a drop in the strength characteristics of the alloys was observed, which can be attributed to the formation of inclined basal texture. On a positive side, an increase in tensile ductility to ~34% for Mg-2.0%Ag and ~27% for Mg-4.0%Ag was observed. This effect can be associated with the activity of basal and prismatic slip induced by ECAP. One of the ECAP regimes tested gave rise to a drop in the corrosion resistance of both alloys. An interesting observation was a cytotoxic effect both alloys had on tumor cells in vitro. This effect was accompanied with the release of lactate dehydrogenase, an increase in oxidative stress, coupled with the induction of NO-ions and an increase in the content of such markers of apoptosis as Annexin V and Caspase 3/7. Differences in the chemical composition and the processing history-dependent microstructure of the alloys did not have any significant effect on the magnitude of their antiproliferative effect.

Effect of Equal-Channel Angular Pressing and Second Phase on Pitting Corrosion of Ultrafine-Grained Steel

Effect of Equal-Channel Angular Pressing and Second Phase on Pitting Corrosion of Ultrafine-Grained Steel

Evolution of Microstructure and Mechanical Properties of Composite Aluminum-Based Alloy during ECAP

The effect of equal-channel angular pressing (ECAP) in an equal-channel stepped die on the microstructure and the mechanical properties of silumin AK9 (Al–Si–Mn–Mg) modified by a master alloy with nanostructured carbon in the form of fullerene black and synthesized glassy carbon particles formed during manufacturing the master alloy is studied. Silumins belong to nondeformable cast alloys; however, ECAP at 500°C makes its plastic deformation up to three passes possible. Three passes of deformation significantly refine the structure of the AK9 modified silumin. ECAP results in the refinement of silicon inclusions, which are of the fabrication origin and do not undergo plastic deformation.

Effect of equal-channel angular pressing and post-aging on impact toughness of Al-Li alloys

Overcoming the toughness inadequacy of Al-Li alloys is in urgent need for developing new low-density and high-performance aerospace aluminum alloys. In this research, continuous equal-channel angular pressing (ECAP) and post-aging were developed to significantly enhance the impact toughness of 1420 Al-Li alloy. The effects of the processes on microstructure evolution, impact absorbed energy and fracture surfaces of 1420 alloy were investigated. The results demonstrated that the impact toughness of ultrafine-grained (UFG) 1420 alloy after 8 ECAP passes at 573 K reached up to 26.6 J/cm2 at room temperature and increased sixfold compared with that of the coarse-grained sample, but the post-aging reduced the beneficial effect. The remarkable improvement after the warm ECAP was mainly due to the UFG microstructure, certain amount of dislocations, and the fine precipitates with uniform distribution, thereby making UFG 1420 alloys more attractive in aerospace applications.

Effect of ECAP temperature on precipitation and strengthening mechanisms of Mg–9Al–1Si alloys

Abstract