Severe Plastic Deformation Method Research Articles

The impact toughness and mechanism of low-carbon steel fracture at low temperatures

The goal of the work is to study the effect of severe plastic deformation (SPD) on the impact toughness and fracture mechanism of St3sp low-carbon structural steel within a test temperature range of 293 – 213 K. The issues of deformation processing of steel St3sp billets using SPD method in conditions of the equal-channel angular pressing scheme (ECAP) are considered. The results of low-temperature tests by impact bending of Charpy steel samples in various states are presented. The impact toughness decreased by ~1.3 times as a result of ECAP in 16 passes. It is shown that the temperature dependence of the impact toughness of steel subjected to ECAP differs from that for steel in the delivery condition. A fractographic study of the fracture mechanisms of the steel in the initial state and after processing by ECAP at a test temperature of 293 – 213 K is carried out. It is shown that for the steel in the initial the transition from fracture with the formation of viscous and brittle fracture zones at 293 K to brittle at 213 K occurs through successive expansion of the brittle fracture area with decreasing temperature, whereas for hardened steel, the mixed fracture area appears in the local region at 233 K and expands to the entire cross section of the sample at 213 K. The microstructure formed as a result of ECAP in 16 passes in the temperature range up to 213 K prevents pure brittle fracture and leads to a mixed fracture pattern.

Micromanufacturing by severe plastic deformation

Beygelzimer Y., Kulagin R., Estrin Y., Davydenko O., Pylypenko A. Micromanufacturing by severe plastic deformation // Material working by pressure. – 2019. – № 2 (49). - Р. 87-90.
 The production of precision small-scale objects is now a rapidly expanding industry worldwide. In English literature, it has been named "Micromanufacturing" and covers the production of meso (1-10 mm) and micro size (1-1000 microns) for aerospace, automotive, optical, biomedical and other engineering fields. Features of "Micromanufacturing" poses the following challenges for material science. First, the mechanical properties of materials for small-sized products are significantly different from those of traditional mechanical engineering. This means that micromanufacturing requires new materials, and in very small quantities, for traditional mechanical engineering quantities. Small-scale production of new materials by traditional metallurgical methods is, at least, unprofitable. Thus, the problem arises to create technologies that allow to produce small batches of various metallic materials with specified properties. Secondly, micromanufacturing requires sub-microcrystalline materials. Finally, to produce a series of identical products from the same workpiece, the statistical variation in the material properties in its bulk is as narrow as possible. Metallurgical methods designed to produce large volume blanks may not provide the degree of uniformity of materials required for micro-production. The article shows that the solution of these three problems is possible by applying the methods of severe plastic deformation.

A new severe plastic deformation method: thin-walled open channel angular pressing (TWO-CAP)

In this study, a novel severe plastic deformation method, named as thin-walled open channel angular pressing (TWO-CAP), was developed and applied to AZ31 magnesium alloy beams in U-type cross-sectional shape. First of all, the principles of the method with all parameters were determined, and the analytical model of the system was generated, and then the study was supported with the numerical analysis. Then, a proper experimental setup was established by considering theoretic outputs. After that, AZ31 magnesium alloy specimens were machined from bulk material in U-type shape as to fit the die channel, and then these specimens were annealed and pressed along the TWO-CAP die. Following the experimental studies, the specimens were tested in order to define the changes in mechanical and microstructural properties. In this stage, the tension test and hardness test were applied to determine the mechanical properties, while optical microscope, scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, and transmission electron microscope analyses were applied to see the changes in microstructure. As a result, an improvement on strength, hardness, and toughness was observed depending on the changes on the microstructure and grain refinement due to the large plastic deformation.

Architectured hybrid conductors: Aluminium with embedded copper helix

This study is inspired by the potential of application-designed aluminium-copper conductors. This work combines recently discovered advantages of hybrids with one constituent having a helical architecture with the benefits provided by severe plastic deformation (SPD) methods. The hybrids are made by embedding copper helixes in melted aluminium and subjecting cast hybrid ingots to different SPD techniques. The electrical conductivity, microstructure features and strength of the produced samples are discussed in relation to effect of SPD and annealing on both constituents and an interface zone formed during the hybrids' production. It was shown that between all processing techniques the reciprocal extrusion (RE) has the great potential for production of lightweight conductors with high conductivity and enhanced strength. A new model describing the effective electrical conductivity of hybrid samples, consisting of an aluminium matrix with an embedded copper helix and intermetallic containing interface, is developed and justified by experimental data. The model is shown to be instrumental for analysis of the effect of the helix's parameters and interface width on effective conductivity of the hybrid samples and could be used for optimal design of hybrid conductors.

Constrained groove pressing process of Al/Cu bimetal sheet

ABSTRACTConstrained groove pressing (CGP) process is a severe plastic deformation (SPD) method to reach to good mechanical and metallurgical properties in sheet metals. In this study, semi-CGP process was performed on the Al/Cu bimetal sheet to investigate the variations in its mechanical and metallurgical properties. The sheet was annealed, and then the CGP-processed. The sheet was fractured after applying two passes (eight steps). Also for studying the strain distribution, the process was simulated using the finite element (FE) method and verified by the experimental test. Results showed that the CGP process increased the yield stress and ultimate tensile strength of the bimetal sheet while reducing its ductility. Grain size was reduced in both Al and Cu layers, and reduction rate in the single-passed sample was greater than the double-passed one. Fracture mode before and after the process was ductile in both layers. FE results indicated that the strain imposed on the Cu layer was lower than the Al layer in all steps.

Investigation of mechanical properties on composite materials by several of severe plastic deformation (SPD) methods

The technology of severe plastic deformation (SPD) is the process on forming metals of large plastic strain that is used for mass production in order to make ultrafine-grained (UFG). Through research on the characterization of aluminium-based composite materials with several SPD methods, the ideal variable will be obtained in producing high-strength materials. The development of a new SPD method driven by requirements simplifies the process, so that it can be applied for mass production, some of the development of SPD technology is able to produce high plastic strain. The market for nanostructured materials produced by SPD technology is in sectors where superior traits such as specific strength is needed. This research is focused on a comparison of several SPD methods; APB, MAF, ECAP-PC and RPRF, in the scope of mechanical characterization on aluminium based composites. Result of mechanical properties obtained, the RPRF method is the best that is able to produce higher mechanical characteristics than other methods. That produces 75.9 VH10 hardness on RPRF, while APB 45.82 VH10, ECAP-PC 66.12 and MAF of 42.9 VH10

Study of the thermal stability of structure and mechanical properties of submicrocrystalline aluminum alloys Al-2.5Mg-Sc-Zr

The paper provides the results of experimental studies of the microstructure, mechanical properties, and corrosion resistance of cast and submicrocrystalline (SMC) aluminum alloys Al-2.5Mg-Sc-Zr with different ratios of scandium and zirconium (Sc + Zr = 0.32 wt.%). SMC structure in alloys was formed by methods of severe plastic deformation: equal-channel angular pressing and rotary swaging. In our paper, we demonstrate that the alloys have high thermal stability – the recrystallization point in SMC alloys is 250-275 °C. We prove that the replacing scandium with zirconium leads to an increase in the thermal stability of the solid solution of scandium in cast and SMC aluminum alloys Al-Mg-Sc-Zr.

Mechanical Properties of Ti-15Mo Alloy Prepared by Cryogenic Milling and Spark Plasma Sintering

Metastable β-Ti alloy Ti-15Mo was prepared by cryogenic ball milling in a slurry of liquid argon. Material remained ductile even at low temperatures, which suppressed particle refinement, but promoted intensive plastic deformation of individual powder particles. Repetitive deformation of powder particles is similar to the multidirectional rolling and resembles bulk severe plastic deformation (SPD) methods. Initial and milled powders were compacted by spark plasma sintering. Sintered milled powder exhibited a refined microstructure with small β-grains and submicrometer sized α-phase precipitates. The microhardness and the yield tensile strength of the milled powder after sintering at 850 °C attained 350 HV and 1200 MPa, respectively. Low ductility of the material can be attributed to high oxygen content originating from the cryogenic milling. This pioneering work shows that cryogenic milling followed by spark plasma sintering is able to produce two-phase β-Ti alloys with refined microstructure and very high strength levels.

Comparison of different methods of Severe Plastic Deformation for grain refinement

The methods of severe plastic deformation are the procedures of grain refinement of bulk crystalline materials to ultrafine or up-to Nano crystalline structure followed by improvement in mechanical properties of different metals and alloys used for various automobile, aerospace and defence applications. In this research paper, discussion has been made about the comparison of different methods of severe plastic deformation for perfection in microstructure and subsequent changes in mechanical properties for industrial applications. The results achieved by Equal Channel Angular Pressing method are more useful for grain refinement by the reason of high imposed shear strain in the material. It has also been observed that using this method strength is also increased with ductility as desired in most of the cases. It can be concluded here that detailed study is still to be explored after processing the material after severe plastic deformation.

Combining methods of severe plastic deformation as an effective way to increase the strength of metallic materials

The article reviews the combined methods of severe plastic deformation (SPD) for hardening metallic materials. The combined deformation processing, extrusion with the equal-channel angular pressing (ECAP) is presented. The comparison is made of the mechanical characteristics and the fracture mode of the Fe360 low carbon steel strengthened by the combined methods of extrusion with ECAP and ECAP with extrusion.

Evolution of Physical and Mechanical Properties of Nanostructured Titanium upon Annealing

Nanocrystalline and submicrocrystalline titanium are synthesized using the methods of severe plastic deformation by twisting and equal channel angular pressing with subsequent cold rolling. The microhardness, magnetic susceptibility, and electrical resistivity have maximum values in highly strained titanium. Annealing in the temperature range of 673–1123 K leads to restoration and recrystallization manifested in decreases in the microhardness by a factor of 2, in the magnetic susceptibility by 15%, and in the resistivity by 20%.

Effect of ultrasonic pretreatment on the superplasticity of titanium alloy Ti-6Al-4V processed by ECAP

Improving the superplasticity characteristics of alloys widely used in industry, such as titanium alloy Ti-6Al-4V, is an important practical problem. Processing by the methods of severe plastic deformation can reduce the temperature of superplasticity. However, the material exhibits high flow stresses. In this work we studied the effect of preliminary ultrasonic treatment with an amplitude of oscillating tension-compression stresses of 100 MPa on the characteristics of superplasticity of the Ti-6Al-4V alloy processed by equal channel angular pressing (ECAP). It is shown that high-frequency oscillating stresses resulted in the reduction of the flow stress, the increase in elongation and the strain rate sensitivity coefficient during tensile tests in the conditions of superplasticity.

Strength and electroconductivity of bulk nanostructured copper alloys

The results of a study of the strength and conductivity of electrotechnical bulk nanostructured copper alloys obtained by methods of severe plastic deformation is presented. The contribution of the microstructure parameters to the formation of high strength while maintaining sufficient electrical conductivity is discussed.

Ion nitriding effect on the structure and mechanical properties of R6M5 high-speed steel after SPD

The paper studies the effect of ion nitriding in a glow discharge on the structure and mechanical properties of R6M5 steel obtained by the method of traditional hot thermomechanical treatment and subsequent severe plastic deformation (SPD). It is found out that the surface microhardness of material increases significantly (~ 1.7 times) as a result of ionic nitriding after SPD and for the sample without SPD an increase is twice as much times in the line region of carbide-nitride inclusions. It is proved that the microhardness distribution over the diffusion zone depth in the sample after the SPD is smoother, and the thickness of the diffusion layer exceeds almost 2 times.

Microstructure and mechanical properties of the Mg–Zn–Ca biodegradable alloy after severe plastic deformation

Mg-Zn-Ca alloys are considered as promising biodegradable metals for implants because of their biocompatibility and proper physical properties. In this study, microstructure and strength of magnesium alloy Mg-1% Zn-0.2% Ca after a combination of the severe plastic deformation (SPD) methods have been investigated. It was shown that with an increase in the degree of deformation, an increase in the strength properties occurs. It was established that the ultimate tensile strength of the initial state was 125 MPa and after SPD a 2-fold increase in strength up to 283.3 MPa was achieved with sufficient ductility.

Features of a severe plastic deformation method for threaded steel reinforcing bars used in construction

Enhancing the mechanical properties of products by developing new technologically advanced SPD methods, as the most efficient for strengthening of materials due to deep refinement of the initial structure, is an urgent task. For this purpose, a method was developed for the continuous forming of threaded rods with the required properties, using successive operations of rolling and transverse shear. The produced rods with a threaded profile can be used in construction as reinforcing bars for the reinforcement of concrete structures. The studies were conducted using mathematical modeling and physical experiments. We analyzed the stress-strain state of the produced billets. In one processing cycle, the strength of the initial billet from low-carbon steel 10 was raised from 350 to 530-550 MPa and simultaneously a threaded profile was formed. The obtained parameters comply with the Russian state standard GOST for steel reinforcing bars of the A500 class used in construction.

A novel single pass severe plastic deformation method using combination of planar twist extrusion and conventional extrusion

Forward shear normal extrusion (FSNE) as a new single pass severe plastic deformation (SPD) method was based on conventional extrusion combined with planar twist extrusion. The proposed method was studied by finite element analysis to investigate the effect of FSNE die geometrical parameters, i.e. deformation zone Length (LDZ) and distortion angle (α), on uniform stress-strain distribution during deformation. Consequently, the optimum condition was considered in design and the process was experimentally performed on aluminum alloy (0.27% Fe, 0.08% Si and balance Al (wt. %). It was found that L = 15 mm and α = 40° are the optimum die parameters that can result in higher effective plastic strain with a more uniform distribution. Microstructural evolution was also studied to demonstrate the capability of this technique in grain refinement and microstructure observations revealed the presence of ultra-fine grains after FSNE. Tensile testing results indicated that yield (YS) and ultimate (UTS) strengths increase 2.7 and 2 times for the processed sample compared to the annealed sample. Hardness results showed increase in hardness level from 25HV0.3/10 for non-processed to 53 HV0.3/10 for the processed state. The uniform distribution of hardness values in both transverse and longitudinal directions was achieved due to the uniform distribution of effective strain resulting from the optimum die design. Compared to other SPD methods, the present technique resulted in high accumulated plastic strain and hardness with uniform distribution and significant grain refinement after one pass.

An experimental investigation on the influence of elevated-temperature constrained groove pressing on the microstructure, mechanical properties, anisotropy and texture of 2024 Al sheets

The constrained groove pressing (CGP) is one of severe plastic deformation (SPD) methods for producing ultra-fine grained sheet metal. The present research work is concerned with CGP process of 2024 Al alloy, with a high strength to weight ratio, at 300 °C, and for three cycles. With this regard, several tensile tests were performed to study the mechanical properties of various samples in different directions. By computing the Lankford anisotropy coefficient, normal and planar anisotropy were determined for specimens produced via up to three CGP passes. Moreover, pole figures (PF) and inverse pole figures (IPF) of various samples were prepared for texture analyses and finding the causes of variations in their UTS, elongation and anisotropy parameters. On the basis of texture analysis, it was found that 1-pass CGP could result in the highest normal anisotropy which means the lowest risk of fracture in a subsequent metal forming process such as deep drawing. The highest texture intensity was also owned by the 1-passed specimen. On the other hand, the 2-passed workpiece demonstrated the lowest absolute planar anisotropy value which could be beneficial for an additional forming operation.

Influence of Combined Severe Plastic Deformation and Sheet Extrusion Process on the Superplastic Formability of AA 5083 Aluminum Alloy Assessed by Free Bulge Test

A combination of two forming operations is considered for producing metal sheets with improved mechanical properties. As the first operation, a newly introduced severe plastic deformation method called dual equal channel lateral extrusion (DECLE) was performed at 300 °C for different passes on the AA 5083 aluminum blocks. Following the DECLE operation, sheet extrusion was conducted to convert the bulk samples, severely deformed through various passes, into 1.8-mm-thick sheets. Mechanical properties of the processed specimens, after each step of deformation, were examined using tensile and shear punch tests. It was found that the material after three passes of DECLE and also the corresponding forwardly extruded sheet presented the greatest strength. In order to evaluate the biaxial formability of the sheets, gas bulge forming tests were conducted using a PLC-controlled gas circuit. It was shown that the material processed via three passes of DECLE operation and extrusion demonstrated the maximum biaxial superplastic formability with an effective strain associated with 400% uniaxial elongation. This sheet specimen also required the minimum forming time, coinciding with a strain rate of 4 × 10−4 s−1, which is higher than strain rate for the sheet extruded from the annealed sample.

Microstructure evolution of ultrafine grained aluminum alloy prepared by large strain extrusion machining during annealing

As a new type of severe plastic deformation (SPD) method for efficiently preparing ultrafine grained (UFG) material, large strain extrusion machining (LSEM) has attracted the attention of researchers. At the same time, the UFG material prepared by the process has a small size, and the influence of external heat is involved in the subsequent utilization. Therefore, in this paper, the microstructure evolution of UFG 6061 Al alloy chips prepared by LSEM during annealing has been investigated. The UFG chips were subjected to isochronous and isothermal annealing treatments. The microstructure of UFG chips was characterized by scanning electron microscope (SEM) with electron backscattered diffraction (EBSD) system. The results showed that with the increase of annealing temperature, the UFG aluminum alloy chips underwent three processes of recovery, recrystallization and grain growth. When the annealing temperature was 160 °C, with the extension of annealing time, the UFG aluminum alloy chips remained at the recovery stage, the point defects and dislocations were reduced, the dislocation density was reduced, and the grain size was not changed significantly.