Influence Of Severe Plastic Deformation Research Articles

Influence of Severe Plastic Deformation on the Magnetic Properties of Sm–Co Permanent Magnets

High pressure torsion (HPT) is presented as a new fabrication route to produce bulk Sm–Co magnets with a strongly refined microstructure down to the nanometer regime. The initial powders, based on the compositions SmCo5, Sm2Co7 and Sm2Co17, are compacted and subsequently deformed by HPT. The microstructural evolution in dependence on the applied deformation parameters is characterized by electron microscopy and the effect of HPT on the phase stability is monitored by synchrotron X‐ray diffraction. An increasing amount of applied strain leads to a stronger reduction in grain size while strain localization counteracts a homogeneous microstructural refinement. The positive effect of elevated deformation temperatures is demonstrated for Sm2Co17, which promotes homogeneous grain refinement, but causes strain‐induced phase transformations at the same time, strongly affecting the magnetic behavior. Superconducting quantum interference device magnetometry is used to characterize the magnetic properties after HPT deformation, which indicates the formation of a magnetic texture depending on the respective phase.

Influence of Severe Plastic Deformation and Aging on Low Cycle Fatigue Behavior of Al-Mg-Si Alloys.

Strain-controlled low cycle fatigue (LCF) tests were conducted on conventionally grained (CG) and ultrafine-grained (UFG) Al-Mg-Si alloys treated under various aging conditions. In the cyclic stress response (CSR) curves, CG peak-aged (PA) alloys showed initial cyclic hardening and subsequent saturation, whereas CG over-aged (OA) alloys displayed cyclic softening behavior close to saturation. The UFG materials exhibited continuous cyclic softening except for UFG 3; it originates from the microstructural stability of the UFG materials processed by severe plastic deformation (SPD). Using a strain-based criterion, the LCF behavior and life of the CG and UFG materials were analyzed and evaluated; the results are discussed in terms of strengthening mechanisms and microstructural evolution. In the CG materials, the LCF life changed markedly owing to differences in deformation inhomogeneity depending on the precipitate state. However, the UFG materials displayed a decreasing LCF life as cyclic softening induced by dynamic recovery became more severe; additionally, a relationship between the microstructural stability of the UFG materials and the cyclic strain hardening exponent n' was suggested.

Microstructure, mechanical properties, and corrosion behavior of a biodegradable Zn–1.7Mg–1Ca alloy processed by KoBo extrusion

The present study investigated the effects of Mg and Ca additions to pure Zn on its microstructure, mechanical properties, and corrosion resistance, as well as the influence of severe plastic deformation via KoBo extrusion on these properties for both pure Zn and the ternary Zn–1.7Mg–1Ca (wt.%) alloy. The microstructural analysis conducted using scanning electron microscopy and electron backscatter diffraction revealed that the addition of alloying elements led to the formation of Mg2Zn11 and CaZn13 intermetallic compounds. The equivalent strain generated via KoBo extrusion was calculated using FORGE® NxT software. The mechanical testing results revealed that the ternary Zn alloy had 186% higher hardness (100 ± 2.6 HV), 210% higher YS (31 ± 3.5 MPa), and 254% higher UTS (85 ± 7.4 MPa) compared to pure Zn. Moreover, the application of KoBo extrusion was found to be beneficial for further enhancing the mechanical properties of both pure Zn and the ternary Zn alloy. Furthermore, the results of the potentiodynamic polarization test performed in Ringer's solution for evaluating the corrosion resistance of the fabricated alloys revealed that the addition of alloying elements increased the corrosion rate by 11% compared to pure Zn (from 145 ± 9 to 161 ± 8 μm/year) due to the micro-galvanic cell formation between different phases, and the KoBo extrusion process increased the corrosion rate of pure Zn but decreased the corrosion rate of the ternary Zn alloy.

Influence of severe plastic deformation of Cu powder and space holder content on microstructure, thermal and mechanical properties of copper foams fabricated by lost carbonate sintering method

Micro-porous copper foam with open cell structure and acceptable mechanical behavior charts a path for developing the supreme chips and integrated circuit due to its large surface area and good thermal conductivity. In this study, semi-open cell structure copper foams were successfully produced using mechanically pre-activated (milled) Cu powders by different milling durations and 50–70 vol% K2CO3 as a filler material by lost carbonate sintering (LCS) method. The effect of mechanical milling of the used powder and volume fraction of K2CO3 on the microstructure, porosity, strength, energy absorption, and the cooling rate of the produced foam was examined. Microstructural analysis showed that long-duration milled powder creates foams with small pores and homogeneous size distribution, leading to plateau stresses up to ≈170 MPa. Cu foam with increased porosity showed a reduction in yield strength, plateau stress, and energy absorption but a significant increase in its cooling rate. The foam with 70% porosity prepared using 2.5h-milled Cu powders exhibited the highest cooling rate. The results of this study show that the fabrication of Cu foams using flake Cu powder obtained from short-time milling yields improvements in the mechanical and thermal performance of the foam. Mechanical milling of the used powder for a longer time leads to a decrease in cooling rate of the produced foam.

Influence of Severe Plastic Deformation by Extrusion on Microstructure, Deformation and Thermal Behavior under Tension of Magnesium Alloy Mg-2.9Y-1.3Nd

The microstructural investigation, mechanical properties, and accumulation and dissipation of energies of the magnesium alloy Mg-2.9Y-1.3Nd in the recrystallized state and after severe plastic deformation (SPD) by extrusion are presented. The use of SPD provides the formation of a bimodal structure consisting of grains with an average size 15 µm and of ultrafine-grained grains with sizes less than 1 µm and volume fractions up to 50%, as well as of the fine particles of the second Mg24Y5 phases. It is established that grain refinement during extrusion is accompanied by an increase of the yield strength, increase of the tensile strength by 1.5 times, and increase of the plasticity by 1.8 times, all of which are due to substructural hardening, redistribution of the phase composition, and texture formation. Using infrared thermography, it was revealed that before the destruction of Mg-2.9Y-1.3Nd in the recrystallized state, there is a sharp jump of temperature by 10 °C, and the strain hardening coefficient becomes negative and amounts to (−6) GPa. SPD leads to a redistribution of thermal energy over the sample during deformation, does not cause a sharp increase in temperature, and reduces the strain hardening coefficient by 2.5 times.

Structural Hierarchy of PA6 Macromolecules after Hydrostatic Extrusion.

This article presents the influence of severe plastic deformation by hydrostatic extrusion (HE) on the thermal and structural properties of polyamide 6 (PA6). During the hydrostatic extrusion process, a fibrous structure oriented along the extrusion direction is formed, which was visualized during microscopic observations. The degree of crystallinity was analyzed by differential scanning calorimetry (DSC). Wide-angle X-ray scattering diffraction (WAXS) analysis was used to partially characterize the PA6 structure after the HE process. The contents of various forms of the crystalline phase in PA6 samples before and after the HE process were analyzed in fragments of spectroscopy in infrared (FTIR). The favorable properties of PA6 after the HE process were obtained after deformation under conditions generating an adiabatic temperature higher than the glass transition temperature and lower than the temperature of the onset of melting of the crystalline phase. Thermal analysis using DSC allowed us to conclude that in the PA6 after the HE process generating deformations in the range of 0.68-1.56, the proportion of the crystalline phase α increases in PA6. As the deformation increases in the HE process, the crystalline phase proportion increases by 12% compared to the initial material (before HE). The glass transition temperature of PA6 is ca. 50.6 °C, reduced for the sample after the HE process at a small deformation of 0.68 (PA6_0.68) to ca. 44.2 °C. For other samples, Tg is ca. 53.2-53.5 °C. As a result of the analysis of WAXS diffractograms of PA6 samples after various deformations in the HE process, the presence of typical peaks of phases α1 and α2 and γ was observed. The results of the FTIR spectroscopic analysis confirm these observations that as the deformation increases, the proportion of the crystalline phase α increases.

Tribological Performance of Laser Shock Peened Cold Spray Additive Manufactured 316L Stainless Steel

Abstract In recent years, cold spray additive manufacturing (CSAM) has become an attractive technology for surface modification and protection. However, due to the intrinsic porous nature of CSAM coatings, they suffer from rapid material degradation due to premature brittle fracturing induced by tribological interactions. In this work, laser shock peening (LSP) was utilized as a post-processing technology to mitigate the surface porosity and augment the surface characteristics of CSAM 316L stainless steel (SS). Due to the synergistic influence of severe plastic deformation and rapid surface heating, the surface porosities were effectively healed, thus reducing the surface roughness. Combined with the surface-strengthening effects of LSP, the frictional resistance and transfer layer formation on the CSAM LSP surfaces were reduced. The underlying mechanisms for these findings were discussed by correlating the atomic, microstructural, and physical features of the LSP surfaces. Based on these findings, it can be suggested that LSP is indeed a useful technique to control the surface characteristics of CSAM 316L SS coatings.

The influence of severe plastic deformation on the thermal expansion of additively manufactured Ti6Al4V alloy

The thermal expansion properties of the Ti6Al4V alloy deposited with direct energy subjected to severe plastic deformation through ECAP were studied in the temperature region 23–700 °C. The deposit samples exhibited two orientations: with the longitudinal axis in the deposition plane and perpendicular to the deposited layers. The microstructure of the deposited alloy and the alloy after thermomechanical treatment was analysed on a scanning electron microscope using the EBSD method. The ECAP process substantially refined the structure of the grains. The temperature dependence of the thermal expansion coefficient estimated for the alloy after ECAP processing exhibited a non-monotonous course. The microstructural changes are the reason for this finding.

Изменение структурно-фазового состояния и механических свойств сплава ВТ35 после интенсивной пластической деформации и последующих отжигов

The influence of severe plastic deformation and subsequent pre-recrystallization annealings on the structural-phase state and mechanical properties of the VT35 titanium alloy has been studied. It is shown that the formation of an ultrafine-grained structure leads to an increase in the mechanical properties of this alloy at room temperature by 65-75% compared to the initial coarse-grained state. It has been established that a significant scatter in the mechanical properties of the alloy after such treatment is due to the inhomogeneity of the distribution of α and β phases in the bulk of the workpieces. Subsequent pre-recrystallization annealings of the VT35 ultrafine-grained alloy at temperatures of 723 and 773 K lead to an additional increase in its mechanical properties (the yield strength and ultimate strength values can exceed 1700 MPa). Using the example of alloy samples after annealing at 723 K for 0.5 h, it is shown that the increase in mechanical properties is due to an increase in the volume fraction of the α-phase due to the β→α phase transformation occurring inside the β phase regions and, as a result, a more uniform distribution of α and β phases.

Fatigue crack growth of deformed pearlitic rail steels under multiaxial loading

A new non-standard experiment is developed to measure fatigue crack propagation in the shear crack growth mechanism occurring in rail and crossing parts. Pre-cracked tubular specimens are loaded under cyclic Mode-II and static compressive Mode-I stresses to reproduce those shear crack growth conditions. To investigate the influence of severe plastic deformation as found in the top of rails in track, specimens are pre-deformed using high pressure torsion. For the pearlitic rail steel, the crack path and crack growth behavior changes distinctively with material pre-deformation: In the undeformed material cracks bifurcate under the Mode-II loading and turn into a Mode-I dominated mixed-mode. After severe plastic deformation, the crack propagates in Mode-II at significantly lower load levels without bifurcating. A detailed analysis of the fracture surfaces as well as the correlation of the crack path and microstructural alignment confirm these findings. Therefore, the proposed experimental procedure could provide Mode-II fatigue crack growth data required to predict crack propagation within rolling contact fatigue in rails and crossings.

Precipitation behavior of a Co-free Fe-Ni-Cr-Mo-Ti-Al maraging steel after severe plastic deformation

Maraging steels are martensitic steels that are strengthened by the precipitation of nano-sized intermetallic phases. Severe plastic deformation is known to influence diffusion, stability and properties of metallic materials. The goal of this study is to reveal the influence of severe plastic deformation on the hardness and the precipitation behavior of a Co-free maraging steel. For this study the as-quenched material was deformed with high-pressure torsion. Afterwards, a series of heat treatments were conducted. The hardness increase was measured and correlated with micro-to-nanoscale microstructural characteristics, focused on the precipitate characterization with atom probe tomography. Severe plastic deformation transformed the microstructure to a globular microstructure, delayed and minimized austenite reversion as well as accelerated and influenced the precipitation reaction, affecting the size, morphology and type of intermetallic phases.

The effect of severe plastic deformation on the IF steel properties, evolution of structure and crystallographic texture after dual rolls equal channel extrusion deformation

This paper presents some results of the influence of severe plastic deformation on the microstructure evolution, grain refinement aspect, and mechanical properties of ultra-low carbon steel. Ti-stabilized experimental IF steel was deformed at a room temperature with unconventional SPD process—dual rolls equal channel extrusion (DRECE). Mechanical properties and structure of ferritic steel in initial state and after selected steps of deformation were investigated. The mechanical properties were determined by static tensile tests carried out at a room temperature and microhardness research. The structural investigations involved using scanning transmission electron microscopy observations, electron back scattered diffraction and measurements of the crystallographic texture. The DRECE process affects the evolution of the structure. The microstructural investigations revealed that the processed strips exhibited a dislocation cell and grain structures with mostly low angle grain boundaries. The electron backscattering diffraction (EBSD) examination showed that the processed microstructure is homogeneous along the strips thickness. The mechanical properties of the DRECE-processed IF steel strips increased with an increase the number of passes.

Influence of severe plastic deformation on superconducting properties of Re and In

The positron lifetime annihilation spectroscopy, magnetic and electrical resistivity data obtained for the pure polycrystalline rhenium and indium samples were compared with corresponding results obtained for samples after severe plastic deformation (rolling at room temperature). In the case of Re, the results clearly show that the superconducting properties of this material can be greatly enhanced by introducing large number of lattice defects into Re matrix. In particular, the rolled Re sample is type-II superconductor with the critical temperature Tc= 2.6 K and the upper critical field μ0Hc2≤0.034 T. Moreover, the resistivity data reveal that in the highly defected parts of the Re metal, the superconductivity emerges at 3.2–3.3 K and the magnetic field of μ0H=0.09 T is not high enough to fully restore the normal state in those parts of the studied material. In contrast to Re, severe plastic deformation performed at room temperature does noticebly not affect the superconducting properties of the In material. The positron lifetime annihilation spectra reveal that the concentration of the lattice defects in the rolled and the annealed samples is close to each other. We conclude that, the observed changes in superconducting properties of rolled Re (this work) and Ta (earlier work) cannot be caused by introducing additional quantities of impurities during rolling procedure and it must be connected with the presence of lattice defects in the rolled foils.

The Influence of Severe Plastic Deformation and Subsequent Annealing on Structure and Mechanical Properties of VT35 Titanium Alloy

The Influence of Severe Plastic Deformation and Subsequent Annealing on Structure and Mechanical Properties of VT35 Titanium Alloy

Advanced materials and technologies for compressor blades of small turbofan engines

BACKGROUND: Manufacturing costs, along with operational performance, are among the major factors determining the selection of the propulsion system for unmanned aerial vehicles (UAVs), especially for aerial targets. OBJECTIVES: In this paper, the design requirements and operating parameters of small turbofan engines for single-use and reusable UAVs are analysed to introduce alternative materials and technologies for manufacturing their compressor blades, such as sintered titanium, a new generation of aluminium and an alloy based on titanium aluminides. METHODS: To assess the influence of severe plastic deformation (SPD) on the hardening efficiency of the proposed materials, the alloys in the coarse-grained and submicrocrystalline states were studied. Changes in physical and mechanical properties of materials were taken into account. The thermodynamic analysis of the compressor was performed in a finite element analysis system (ANSYS) to determine the impact of gas pressure and temperature on the aerodynamic surfaces of compressor blades of all stages. RESULTS: Based on thermal and structural analysis, the stress and temperature maps on compressor blades and vanes were obtained, taking into account the physical and mechanical properties of advanced materials and technologies of their processing. The safety factors of the components were established based on the assessment of their stress-strength reliability. Thanks to nomograms, the possibility of using the new materials and the technologies was confirmed in view of the permissible operating temperature and safety factors of aerofoils. CONCLUSIONS: The proposed alternative materials and production technologies for the compressor blades and vanes meet the design requirements of the turbofan at lower manufacturing costs.

A review paper on magnesium alloy fabricated by severe plastic deformation technology and its effects over microstructural and mechanical properties

Abstract This review paper mainly focused on microstructural and mechanical properties ofultrafine grained nanocrystalline (Nc) Magnesium alloy fabricated by Severe Plastic Deformation(SPD) process. The influence of SPD over mechanical, microstructural, physical, optical, and corrosion properties of Nanocrystalline magnesium alloy are detailed and discussed. It has been observed that nanocrystalline (Nc) magnesium materials has shown superior properties over the bonding of grains while during the Extrusion, Annealing, quenching, Normalizing, Spark Plasma Sintering (SPS) processes. The outcome based by many researchers showed that nanocrystalline Magnesium alloy processed by Severe Plastic Deformation (SPD) showed an improved properties over the Hardness, Dislocation density, Compressive, Tensile and texture, and it’s found to be increased up to certain limit beyond that decrease of microstructural stability, micro hardness and dislocation density were seen to be observed. The Microstructural and Mechanical properties are well improved by Spark Plasma Sintering (SPS), Extrusion, Annealing, Equal channel angular pressing (ECAP), Accumulative Roll Bonding (ARB) and High-Pressure Torsion (HPT) processes. Grain growth Mechanism, Energies Activation during grain growth, Thermal stability, Relative density and stress corrosion rate were observed by previous Researchers during Fractography analysis over several nanocrystalline (Nc) Magnesium alloy specimens.

Influence of severe plastic deformation and some additives on hydrogenation of ZK60 alloy

Using ZK60 commercial magnesium alloy as hydrogen storage material, the effects of equal channel angular extrusion (ECAP) passes and different weight percentages of additives (activated carbon, vanadium and titanium) on hydrogen absorption characteristics were studied. ECAPed ZK60 with additives was prepared by high-energy ball milling for 20 h.The rate of hydrogenation was measured at different temperatures for five cycles using a Sievert's apparatus. The results reveal that hydrogen absorption increased to 5.3 wt% after 12 passes of ECAP in monolithic ZK60. The 12-pass ECAPed ZK60 along with the addition of 5 wt% activated carbon, and 2 wt% vanadium has improved hydrogenation to 6.7 wt% at 350 °C. The hydrogen absorption capacity is increased after each cycle for most ECAPed ZK60 samples, except that doped with 10 wt% activated carbon and 2 wt% titanium in which hydrogen absorption capacity is significantly reduced from 5.6 wt% to 3.2 wt% after the first cycle at 300°C.

Advanced Materials and Technologies for Compressor Blades of Small Turbofan Engines

Manufacturing costs, along with operational performance, are among the major factors determining the selection of the propulsion system for unmanned aerial vehicles (UAVs), especially for aerial targets and cruise missiles. In this paper, the design requirements and operating parameters of small turbofan engines for single-use and reusable UAVs are analysed to introduce alternative materials and technologies for manufacturing their compressor blades, such as sintered titanium, a new generation of aluminium alloys and titanium aluminides. To assess the influence of severe plastic deformation (SPD) on the hardening efficiency of the proposed materials, the alloys with the coarse-grained and submicrocrystalline structure were studied. Changes in the physical and mechanical properties of materials were taken into account. The thermodynamic analysis of the compressor was performed in a finite element analysis system (ANSYS) to determine the impact of gas pressure and temperature on the aerodynamic surfaces of compressor blades of all stages. Based on thermal and structural analysis, the stress and temperature maps on compressor blades and vanes were obtained, taking into account the physical and mechanical properties of advanced materials and technologies of their processing. The safety factors of the components were established based on the assessment of their stress-strength characteristics. Thanks to nomograms, the possibility of using the new materials in five compressor stages was confirmed in view of the permissible operating temperature and safety factor. The proposed alternative materials for compressor blades and vanes meet the design requirements of the turbofan at lower manufacturing costs.

Influence of severe plastic deformations in the bridgman anvil on lattice parameters and microhardness of ferromagnetic metals

The influence of severe plastic deformation by torsion in the Bridgman anvil on the lattice parameters of pure ferromagnetic metals Ni and Co is investigated by x-ray diffraction analysis. It is shown that torsion combined with strong compression leads to decrease in the lattice of these metals and to the change in the level of crystal lattice microstrains. The mechanisms of deformation influence on the lattice parameters are proposed.

The Influence of Severe Plastic Deformation on Microstructure and In Vitro Biocompatibility of the New Ti-Nb-Zr-Ta-Fe-O Alloy Composition.

In this work, severe plastic deformation (SPD) of the newly designed Ti-Nb-Zr-Ta-Fe-O GUM metal was successfully conducted at room temperature using high speed high pressure torsion (HSHPT) followed by cold rolling (CR) to exploit the suitability of the processed alloy for bone staples. The Ti-31.5Nb-3.1Zr-3.1Ta-0.9Fe-0.16O GUM alloy was fabricated in a levitation melting furnace using a cold crucible and argon protective atmosphere. The as-cast specimens were subjected to SPD, specifically HSHPT, and then processed by the CR method to take the advantages of both grain refinement and larger dimensions. This approach creates the opportunity to obtain temporary orthopedic implants nanostructured by SPD. The changes induced by HSHPT technology from the coarse dendrite directly into the ultrafine grained structure were examined by optical microscopy, scanning electron microscopy and X-ray diffraction. The structural investigations showed that by increasing the deformation, a high density of grain boundaries is accumulated, leading gradually to fine grain size. In addition, the in vitro biocompatibility studies were conducted in parallel on the GUM alloy specimens in the as-cast state, and after HSHPT- and HSHPT+CR- processing. For comparative purposes, in vitro behavior of the bone-derived MC3T3-E1 cells on the commercially pure titanium has also been investigated regarding the viability and proliferation, morphology and osteogenic differentiation. The results obtained support the appropriateness of the HSHPT technology for developing compression staples able to ensure a better fixation of bone fragments.