Plastic Deformation Method Research Articles

Realizing ultrafine grain structure of Cu-Cr-Zr alloy via friction stir welding / processing

40 mm thick coarse-grained (up to 10 – 20 mm) CuCrZr mold wall to 2 mm thick pure copper plate lap joint was performed using friction stir welding (FSW) operating a H13 die steel tool. The obtained defect-free joint indicates the potential of FSW to restore worn-out copper molds wall. FSW resulted in ultrafine microstructure (0.5 –1.0 µm) of stir zone strengthened by chromium and Cu5Zr nanoparticles. Grain boundary and dispersion hardening increase the hardness of the stir zone up to 150 –190 HV1 compared to 110 –130 HV1 of the initial coarse-grained structure. Based on the results, friction stir welding and related friction stir processing technologies are proposed as a severe plastic deformation method to obtain an ultrafine-grained state of CuCrZr alloys.

Correction to: Researches on a Novel Severe Plastic Deformation Method Combining Direct Extrusion and Shearings for AZ61 Magnesium Alloy Based on Numerical Simulation and Experiments

Correction to: Researches on a Novel Severe Plastic Deformation Method Combining Direct Extrusion and Shearings for AZ61 Magnesium Alloy Based on Numerical Simulation and Experiments

Numerical-experimental study of die geometry in the constrained groove pressing of 6061 aluminum sheets

Nowadays, in line with the need of different industries to the materials with high strength to weight ratio, researchers have drawn attention to the processes of severe plastic deformation. The constrained groove pressing (CGP) is one of the most effective methods of severe plastic deformation to produce high-strength sheet metal using two dies with different shapes (grooved and flat). Despite the advantages of CGP in creating high accumulative plastic strain, this process leads to non-uniformity in mechanical properties of the sheet. This non-uniformity is one of the limitations of the CGP process which is considered in this study. Experimental and numerical studies were performed to investigate CGP process on 6061 aluminum alloy sheet up to two complete passes and the mechanical properties of the sheets were studied. Hardness testing was conducted on the worked material and the increase in the hardness of tested material in both longitudinal and thickness directions were observed. Also, it was shown that the non-uniformity in hardness distribution is correlated to the non-uniformity in the strain distribution. So, validated numerical model was used to develop the response surface method (RSM) and consequently to investigate the effect of geometric parameters in the grooved die on the strain uniformity. Finally, die geometry was optimized using the developed RSM model to produce a sample with more uniformity in strain and hardness distribution.

Structure and Mechanical Properties of Titanium Processed by Twist Extrusion and Subsequent Rolling

The article considers one of the combined methods of severe plastic deformation (SPD), which includes twist extrusion (TE) and subsequent rolling. The use of combined forming methods is promising for industrial use. Titanium grade 1 was used as a material in the experiments. Rolling was carried out in three stages with a decrease in temperature from 350°C to 180°C for a number of passes with one heating. The accumulated strain degree was e = 4.6 at twist extrusion and e = 3 in rolling. Increasing the reduction per pass decreases the number of heatings and increases the efficiency of the rolling process in whole. At the same time, it is necessary to set the maximum processing modes at which recrystallization processes do not occur in the billet. When rolling, the deformation degree in one pass was taken in the range of 5–20% with an increase in successive passes. The use of such deformation degrees allowed reducing the grain size in titanium grade 1 significantly. Twist extrusion reduces the grain size to 300–500 nm. Subsequent rolling allowed reducing the size of structural elements to 50–100 nm and provided a significant increase in the mechanical characteristics of the billet material (up to 869 MPa) while maintaining satisfactory ductility (up to 11.6%). It was found that increasing the deformation degree in one pass up to 40% at cross-rolling and simultaneously increasing the temperature to 385°C led to a decrease in the UFG structure quality and reduced strength of the deformable material by starting the dynamic recrystallization process.

ЭВОЛЮЦИЯ КОНСТРУКЦИИ МНОГОКОНТАКТНОГО ВИБРОУДАРНОГО ИНСТРУМЕНТА И ОСНОВНЫЕ ПУТИ ЕГО РАЗВИТИЯ

Methods of surface plastic deformation are considered and a generalized model of a tech-nological system for finishing and strengthen-ing dynamic processing by surface plastic de-formation is proposed. Based on the analysis of the issue and the prospects for the devel-opment of the method of multi-contact vibra-tion shock treatment, an algorithm for the modernization of a multi-contact vibration shock tool is proposed. The scheme of the tool for strengthening hole processing is presented, the main directions of the tool evolution are indicated.

The effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy as a biomaterial: A pilot study.

Recently, AZ31B magnesium alloy has been widely employed in automotive, aerospace, and bio implant industries due to its light-weight and biocompatibility properties. However, the equilibrium of ductility and strength of this material and the negativity brought by its poor wear behavior have limited its versatile use. Friction stir processing (FSP) has been commonly used as severe plastic deformation method for improving mechanical and tribological properties of metal sheets. The effect of this method on the biocompatibility of materials is a matter of curiosity that should be emphasized. So, the present study aims to investigate the effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy. It is observed that FSP enhanced the tensile properties of the alloy but decreased its elongation. It was determined that the base material exhibited ductile character on the fracture surface of the specimens, and mixed ductile/brittle fracture was evident with the FSP. In the FSP zone, the hardness value was improved by 17% compared to the base material. Also, the wear performance of the alloy enhanced in ambient air and Simulated Body Fluid (SBF) solution. Wear properties in SBF solution were better due to less adhesive bonds between the friction surfaces. This assessment was supported by SEM images of the wear path and surface of counter bodies. On the other hand, FSPed AZ31B alloy materials with improved strength properties were not cytotoxic for human gingival fibroblasts, and these results may suggest that the materials are safe for clinical uses.

An Overview of Deformation Path Shapes on Equal Channel Angular Pressing

In recent years, research on ultra-fine grain materials has gained attention. While attempts have been made to improve the properties of the material, it has also become increasingly important to decrease the costs. Studies on improving material properties have revealed new production methods or have required the revision of existing production methods. In this direction, severe plastic deformation methods have come to the fore as a good alternative, and by improving the methods with new variations, materials with grain sizes below 1 µm have been obtained. In addition, this method positively affects the mechanical properties of the material. In this study, the Equal Channel Angular Pressing (ECAP) method, one of the severe plastic deformation methods, which has attracted great attention among researchers, was examined and the development stages of the method were investigated according to recent studies. The effective parameters in the method were examined and the effects of these parameters on the grain structure and mechanical properties of the material were discussed. Channel shapes, which are open to innovation and increase the efficiency of the ECAP method, were kept in the foreground among the prominent parameters in the ECAP process, and the results of the design changes made with new variations were examined.

Interaction between disclinated non-equilibrium grain boundaries and radiation-induced interstitial/vacancy in tungsten

Experimental works show that there are plenty of disclinated non-equilibrium grain boundaries (GBs) in polycrystalline materials obtained by the severe plastic deformation method. How these GBs affect the irradiation-induced defects is still an open question. In the present work, molecular dynamics simulation was used to investigate the interaction between disclinated non-equilibrium GBs and irradiation-induced interstitial/vacancy in tungsten. There exists a long-range stress field around the disclinated non-equilibrium GBs. Such a long-range stress field leads to strong interaction between interstitial/vacancy and the GB. The interaction energy calculations suggest that interstitial and vacancy can be attracted strongly by non-equilibrium GBs containing negative and positive disclinations, respectively. This unique interaction behavior is further confirmed by diffusion of interstitials/vacancies near these GBs. The present work clearly demonstrates that disclinated non-equilibrium GBs are stronger irradiation-induced defect sinks than their equilibrium counterparts. So increasing the proportion of disclinated non-equilibrium GBs may be an effective way to develop new-generation irradiation-resistant materials.

Microstructure evolution and mechanical properties of industrial scale samples of Mg–Gd–Y–Zn–Zr alloy after repetitive upsetting-extrusion process

As one of the severe plastic deformation (SPD) methods, repetitive upsetting-extrusion (RUE) technique was an effective way to refine grains for large-sized billet at blank-making stage. The microstructure evolution and mechanical properties of industrial-scale Mg–9Gd–3Y–2Zn–0.4Zr (wt.%) alloys were comprehensively investigated in this paper. The experimental alloys exhibited heterogeneous microstructure in the different regions and directions due to the uneven deformation temperature and strain during the RUE deformation process. In addition, the texture and mechanical properties of the RUEed samples also exhibited obvious anisotropy. In particular, the RUEed sample in the edge region along extrusion direction (EED) showed a superior tensile strength with ultimate tensile strength (UTS) of 357 MPa, tensile yield strength (TYS) of 242 MPa and the failure elongation (FE) of 9.0%, due to the smaller average grain size (12.7 μm) and higher area fraction of the dynamic recrystallized (DRXed) grains (82.2%) than other regions. Furthermore, the results also exhibited that the enhancement of the mechanical properties of the RUEed samples were mainly attributed to Hall–Petch strengthening, Orowan strengthening and texture strengthening.

Dynamic recrystallization behavior and strengthening mechanism of Mg–Gd–Y–Zn–Zr alloy during isothermal MDF process

As one of severe plastic deformation (SPD) methods, multi-directional forging (MDF) technology is an effective way to refine grains. The microstructure, texture evolution and mechanical properties of homogenized Mg–13Gd–4Y–2Zn–0.5Zr (wt. %) alloy during isothermal MDF process were synthetically investigated in the paper. The results showed that the mean grain size of the alloy decreased gradually with the MDF passes increased. After 4 passes, the average grain size of the alloy was refined to 2.7 μm, and the microstructure distribution was uniform. On the one hand, with the increasing of the MDF passes, the massive intergranular LPSO phases are gradually broken up and formed a deformation zone. The plate-like Mg5(Gd,Y) precipitates were located interior the grains. On the other hand, the spherical Mg5(Gd,Y) phases were randomly distributed with the increasing of MDF passes. In addition, the maximum texture intensity of the MDFed alloy on (0001) basal plane gradually was weaken from 15.993 of the 1MDFed alloy to 4.245 of the 4MDFed alloy, which was attributed to the increasing of volume fraction of dynamic recrystallized (DRXed) grains via MDF method. And the dynamic recrystallization (DRX) mechanisms were continuous DRX (CDRX), discontinuous DRX (DDRX), particle stimulated nucleation (PSN) and kink induced DRX. The maximum ultimate tensile strength (UTS) and tensile yield strength (TYS) after 4 passes were 385 MPa and 360 MPa respectively. The excellent mechanical properties of the alloy were owing to the grain boundary strengthening, dislocation strengthening, texture strengthening and precipitation strengthening. In addition, the second phase particles such as lamellar LPSO phases, broken block-shaped LPSO phases, spherical Mg5(Gd,Y) phases and plate-like Mg5(Gd,Y) phases were demonstrated to be the strengthening phases.

Influence of low-temperature heat treatment on microstructure and mechanical properties of hydrostatically extruded titanium

• Titanium processed by hydroextrusion is a highly nonhomogeneous material. • Continuous dynamic recrystallization operates during the later stages of processing. • Low-temperature heat treatment increases ductility significantly. Subjecting a material processed by a Severe Plastic Deformation method to low-temperature heat treatment has not been the subject of any study so far. Therefore, hydrostatically extruded titanium has been examined within the present work with respect to its mechanical properties and microstructure upon heat treatment at 200 °C. Static tensile tests as well as microstructural analyses with the use of electron backscatter diffraction and transmission electron microscopy have been realized. Even though the material has been annealed, deformation-induced defects were still present within the microstructure what proves that continuous dynamic recrystallization dominates at the later stages of the processing. A significant increase in ductility of a heat-treated material compensates the drop in its tensile properties. Low-temperature annealing might provide an initial solution for resolving the strength-ductility paradox in materials processed by Severe Plastic Deformation techniques.

MODIFICATION OF STRUCTURE AND PROPERTIES OF NANOSTRUCTURED VT1-0 TITANIUM ALLOY UNDER ULTRASONIC INFLUENCE

The effect of ultrasonic influence on the structure evolution and creep of nanostructured titanium alloy of the grade VT1-0 obtained by the method of severe plastic deformation has been studied. It is shown that ultrasonic influence with a frequency of f = 20 kHz and an amplitude of 65 MPa leads to relaxation of internal stresses in the nanostructured VT1-0 alloy due to the formation of an equilibrium structure of boundaries without noticeable grain growth. In this case, the mechanical properties of the alloy change as follows: the tensile strength increases, while maintaining the yield strength and ductility. The reason for the observed effect may be the low stacking fault energy of the VT1-0 alloy, which complicates the course of relaxation processes, as well as the rearrangement of the structure during creep with the formation of new deformation boundaries, which are more resistant to tensile loads.

Formation of nanocrystalline grain structure in an Mg-Gd-Y-Zr alloy processed by high-pressure torsion

In this paper, the microstructural and hardness evolutions of an Mg-5.91Gd-3.29Y-0.54Zr (wt%) alloy during high-pressure torsion (HPT) were investigated. Deformation twinning played a crucial role in the HPT-induced grain subdivision process. In the 1/8-revolution disk, 101¯1 and 101¯2 twins with different twin variants, 101¯1−101¯2 secondary twins and twin-twin interactions were activated. Primary twins prevailed at the very central region of the disk, while much finer multiple twins were formed at the edge region of the disk corresponding to the area subjected to a relatively large plastic strain. Besides, dislocation cell substructures were also developed. Nanocrystalline structure was attained after 5-revolution HPT processing, and the maximum hardness reached ~120 Hv at the edge region of the disk, which is much higher than that achieved from other traditional plastic deformation methods.

МЕТОДИ ВИМІРЮВАННЯ ТИСКУ ПОРОХОВИХ ГАЗІВ

The article analyzes possible methods for measuring the pressure of powder gases. The phenomenon of a shot is very complex. Many components of the processes themselves are very complex, interconnected one with the other and strongly depend on the scheme of the device and the design of the weapon, the powder charge and the projectile, on the properties of the gunpowder and on the state of the atmosphere in which the projectile moves. In addition, most of the processes of the phenomenon of a shot occur in very short periods of time and are characterized by high values of physical parameters: speed, pressure, temperature. The complexity and intensity of the phenomenon of a shot do not allow us to study it in full. Therefore, in ballistics they confine themselves to studying the basic regularities of the phenomenon of a shot, on which the movement of a projectile depends very much. This study, necessary for artillery practice, is carried out by theoretical and experimental methods. The parameters of the state of powder gases, as well as a number of parameters of most firing processes that are not directly measured, have to be determined indirectly, primarily from the results of measuring the pressure of powder gases. For this, various laws and relations established on the basis of theoretical and experimental research are usually used, which connect the desired quantities with the pressure of powder gases. Static pressure measurement methods are based on the principle of converting pressure values into strain values or other physical quantities associated with it. Dynamic pressure measurement methods are based on the principle of converting pressure values into kinematic elements of motion: acceleration, speed or path as a function of time. Keywords: pressure, static pressure measurement methods, dynamic pressure measurement methods, tensometric method, piezoelectric method, plastic deformation method, spring deformation method.

An extrusion−shear−expanding process for manufacturing AZ31 magnesium alloy tube

A new severe plastic deformation method for manufacturing tubes made of AZ31 magnesium alloy with a large diameter was developed, which is called the TCESE (tube continuous extrusion−shear−expanding) process. The process combines direct extrusion with a two-step shear−expanding process. The influences of expanding ratios, extrusion temperatures on the deformation of finite element meshes, strain evolution and flow velocity of tube blanks during the TCESE process were researched based on numerical simulations by using DEFORM-3D software. Simulation results show that the maximum expanding ratio is 3.0 in the TCESE process. The deformation of finite element meshes of tube blanks is inhomogeneous in the shear−expanding zone, and the equivalent strains increase significantly during the TCESE process of the AZ31 magnesium alloy. A extrusion temperature of 380 °C and expanding ratio of 2.0 were selected as the optimized process parameters from the numerical simulation results. The average grain size of tubes fabricated by the TCESE process is approximately 10 µm. The TCESE process can refine grains of magnesium alloy tubes with the occurrence of dynamic recrystallization. The (0001) basal texture intensities of the magnesium alloy tube blanks decrease due to continuous plastic deformation during the TCESE process. The average hardness of the extruded tubes is approximately HV 75, which is obviously improved.

On the solution treatment of severely deformed AA2024-O and subsequent natural aging

In this research, the effect of applying severe strain before solid solution treatment (SST) for AA2024-O was studied. Providing concurrent insights into solutionizing behavior and microstructural evolution corresponding to hardness is important. Multi-directional forging (MDF) was used as a severe plastic deformation (SPD) method. After applying SST on MDFed (4 passes) and as-annealed samples, natural aging (NA) was used as the following treatment to examine the role of severe strain on the solutionizing behavior. In most previous attempts, SPD has been used after SST, but one of the innovations of the present work is the study of SPD before SST. Experimental results show that adding a severe strain using the MDF method before SST results in a significant refinement in the grain size of the solutionized recrystallized microstructure (47 μm). In contrast, coarse-grained microstructures with grain sizes of 150 μm–300 μm are used in prior tries. The results indicate that continuous static recrystallization (CSRX) with a grain size of 47 μm occurs during the solution treatment of the MDFed sample, which is 220% less than that during solution treatment of the as-annealed sample (150 μm); also, rich presence of the second phase particles after its aging by FE-SEM was analyzed. By measuring the difference in hardness before and after NA in solution-treated MDFed and as-annealed samples, 500 °C and 5 min were found to be the most desirable temperature and times in terms of mechanical properties and microstructure. While, in previous efforts, no suitable time has been found for solution treatment of this alloy, and times of 2 h–24 h have been used. The present work found a suitable time of 5 min for solution treatment, which has significant energy savings. In the solution-treated MDFed sample, the maximum hardness of NA (100 HV) was reported; additionally, the percentage of increase in hardness before and after NA (ΔH %) for solution-treated MDFed and as-annealed samples were obtained at 43% and 23%, respectively. Using the DSC test, it was found that in the solution-treated MDFed sample, the peak of S′/S (Al2CuMg) phase formation spreads and shifts from 262 °C to a lower temperature of 235 °C. Using Johnson-Mehl-Avrami (JMA) equations, the values of 103 kJ/mol and 108 kJ/mol were obtained for the activation energy of solution-treated MDFed and as-annealed samples, respectively. Lower activation energy means utilizing Severe Plastic Deformation (SPD) before SST generates a high density of dislocations and vacancies that accelerate solute atoms dissolution and provide S′/S -phase nucleation sites.

Способы ультразвукового поверхностного пластического деформирования

The existing classification features of ultrasonic surface plastic deformation methods are viewed and their technological capabilities are studied. Methods of ultrasonic surface plastic deformation classification are proposed

Formation of ultrafine grains in magnesium alloy during dynamic extrusion at room temperature

Magnesium alloy is a class of lightweight structural materials with promise for many applications. Here, the authors report a significant grain refinement, high deformation twin density and obvious nanograined structures in magnesium alloy through a novel high strain rate plastic deformation method—dynamic extrusion. By using finite element simulation and transmission electron microscopy (TEM), the authors find that the stain rate during plastic deformation affects the microstructure evolution process, which results in the dynamic deformation mechanisms transition. The results are of interests not only for understanding the deformation mechanisms under dynamic plastic deformation but also for nanostructures formation of the magnesium alloy.

Finite element analysis of the springback behavior after V bending process of sheet materials obtained by Differential Speed Rolling (DSR) method

The Differential Speed Rolling (DSR) process is a severe plastic deformation method used in the production of microstructured materials with both high deformation and superior mechanical properties. This study has focused on determining the springback behavior and formability of the materials obtained by using the DSR method after the V bending process. Rolling processes were carried out at 4 different rolling speed ratios (1.0, 1.33, 1.66, and 2.0), 25% thickness reduction ratio, and 2 different rolling temperatures (room temperature and 580 °C). Then, the rolled sheet materials were bent using 3 different bending die angles (60°, 90°, 120°). As a result of this study, the greatest plastic deformation was reached at a speed ratio of 2.0 at 580 °C. Again, the lowest springback was obtained at 580 °C. As the die angle increased, the springback decreased. Springback has occurred in the bending process of all sheet materials obtained by rolling. In the bending process of the unrolled sheet material, both spring-forward and springback events were observed depending on the die angle.

Development of Ultrafine–Grained and Nanostructured Bioinert Alloys Based on Titanium, Zirconium and Niobium and Their Microstructure, Mechanical and Biological Properties

For this paper, studies of the microstructure as well as the mechanical and biological properties of bioinert titanium, zirconium, and niobium alloys in their nanostructured (NS) and ultrafine-grained (UFG) states have been completed. The NS and UFG states were formed by a combined two-step method of severe plastic deformation (SPD), first with multidirectional forging (MDF) or pressing into a symmetrical channel (PSC) at a given temperature regime, and then subsequent multi-pass groove rolling (MPGR) at room temperature, with pre-recrystallization annealing. Annealing increased the plasticity of the alloys in the NS and UFG states without changing the grain size. The UFG structure, with an average size of structural elements of no more than 0.3 μm, was formed as a result of applying two-step SPD and annealing. This structure presented significant improvement in the mechanical characteristics of the alloys, in comparison with the alloys in the coarse-grained (CG) or small-grained (SG) states. At the same time, although the formation of the UFG structure leads to a significant increase in the yield strength and tensile strength of the alloys, their elastic modulus did not change. In terms of biocompatibility, the cultivation of MG-63 osteosarcoma cells on the polished and sandblasted substrates demonstrated high cell viability after 10 days and good cell adhesion to the surface.