Effect Of High-pressure Torsion Research Articles

Effect of high pressure torsion on magnetic properties and corrosion resistance of MnBi/NdFeB composite magnets

The MnBi/NdFeB composite magnets have been fabricated by high pressure torsion (HPT). The effects of NdFeB content, torsional pressure and torsional degree on the microstructures, magnetic properties, and corrosion resistance of the MnBi/NdFeB composite magnets are systematically investigated. The results show that the remanent magnetization (Mr) of MnBi/NdFeB composite magnets increases with the Nd2Fe14B content. A peak value of the maximum energy product ((BH)max) = 5.61 MGOe is obtained while the Nd2Fe14B content is 75 wt%. Addition of MnBi increases the coercivity temperature coefficient and the density of MnBi/NdFeB composite magnets. The MnBi/NdFeB composite magnets prepared by HPT show perpendicular anisotropy, which can be explained by the (0kl) texture in the perpendicular direction observed by TEM. With the increase of degree of HPT, the intrinsic coercivity (Hcj) difference between perpendicular direction and parallel direction is more obvious, the (0kl) texture is enhanced by the degree of HPT. The first-order reversal curve (FORC) demonstrates that MnBi/NdFeB composite magnets exhibits weaker exchange coupling compared with pure MnBi magnet. Besides, a remarkably improvement in electrochemical stability for the MnBi/NdFeB composite magnet is achieved with the MnBi added.

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.

Effect of high-pressure torsion on the structure and microhardness of biodegradable Fe-30Mn-5Si (WT.%) alloy

The effect of high-pressure torsion (HPT), including a new method of accumulative HPT (AccHPT), on the microstructure and mechanical properties of Fe-30Mn-5Si alloy is studied. It is shown that during HPT and AccHPT, stress-induced ε-martensite is predominantly formed, and a mixture of nanograined structure, nanosubgrained structure and highly-dislocated substructure after HPT, while predominantly nanograined structure after AccHPT, are obtained. The increase in the number of HPT revolutions results in a broadening of the X-ray diffraction lines and higher microhardness values. The highest values were achieved on samples after AccHPT.

Effect of high-pressure torsion and subsequent annealing on mechanical properties of alloy Al—4% Cu—3% Mn

Effect of high-pressure torsion and subsequent annealing on mechanical properties of alloy Al—4% Cu—3% Mn

Interfacial characteristics of multi-material SS316L/IN718 fabricated by laser powder bed fusion and processed by high-pressure torsion

This study focuses on investigating the microstructure and mechanical properties across the interface of a multi-material, Austenitic Stainless Steel 316 L (SS316L) and Inconel 718 (IN718), fabricated using laser powder bed fusion (LPBF) additive manufacturing (AM) technique. Challenges such as distortion, porosity, and intermetallic formation are common in such structures. To address these challenges, high-pressure torsion (HPT), a severe plastic deformation (SPD) process, was employed to eliminate porosity and create a homogeneous microstructure. The samples underwent HPT with varying numbers of turns, namely quarter, half, one, five, and ten turns, at room temperature and under 6 GPa of pressure at a speed of 1 rpm. The process aimed to create ultrafine and nano-grains in the microstructure and reduce the defects. A comprehensive characterization approach was adopted to analyze the interface. The results showed reduced porosity, improved bonding, and enhanced material density through HPT. X-ray diffraction (XRD) analysis confirmed the retention of the austenitic face-centered cubic (FCC) phase in both materials. The dislocation density reached a saturation point of 1.85 × 1015 m−2, while the crystallite size decreased to 26 nm. Transmission electron microscopy (TEM) analysis provided insights into the microstructure, showing dislocation networks at lower torsional strain and homogenous nano-grains at higher torsional strain. Vickers microhardness and nanoindentation measurements demonstrated an increase in hardness with increasing torsional strain, with the peripheral region exhibiting rapid hardness saturation and the central region showing lower hardness due to reduced strain. Overall, this study provides valuable insights into the effects of HPT on multi-material SS316L/IN718, contributing to the understanding of their interfacial characteristics and enhanced utilization of multi-materials in various engineering applications.

Effect of High-Pressure Torsion on Phase Formation and Mechanical Properties of a High-Entropy TiZrHfMoCrCo Alloy.

This investigation delved into the alterations in the mechanical properties of a TiZrHfMoCrCo high-entropy alloy due to phase transformations induced by high-pressure torsion (HPT). The alloy's genesis involved levitation melting within an argon atmosphere, presenting two distinct states for analysis: the initial, post-manufacturing state and the state subsequent to HPT treatment. The original alloy featured a composition comprising a singular A2 phase with a bcc lattice and two Laves phases, C15 and C14. The HPT process triggered significant phase modifications: a retention of one C15 Laves phase and decomposition of the bcc phase into two distinct phases exhibiting different bcc lattice parameters. The HPT-induced effect prominently manifests as strong grain refinement. However, scanning electron microscopy (SEM) observations unveiled persistent inhomogeneities at a micron scale both before and after HPT treatment. Thus, grain refinement occurs separately within each of the bcc and Laves phases, visible in the light, dark, and gray areas in SEM images, while mixing does not occur on the scale of several microns. The examination of Ti, Cr, Co, Zr, Mo, and Hf via X-ray absorption spectroscopy (EXAFS) at specific K-edges and L3-edge revealed that the HPT treatment conserves the local atomic environment of metal atoms, albeit with a slight elevation in static disorder. Assessments through microhardness and three-point bending tests demonstrated the material's inherent hardness and brittleness. The microhardness, standing at a substantial value of 600 HV, displayed negligible augmentation post-HPT. However, the microhardness of individual phases exhibited a notable alteration, nearly doubling in magnitude.

Effect of Nanostructuring on Operational Properties of 316LVM Steel

In this study, high-pressure torsion (HPT) was used to process austenitic 316LVM stainless steel at 20 °C and 400 °C. The effects of HPT on the microstructure, mechanical, and functional properties of the steel were investigated. By applying both HPT modes on the 316LVM steel, a nanocrystalline state with an average size of the structural elements of ~46–50 nm was achieved. The density of the dislocations and twins present in the austenite phase varied depending on the specific HPT conditions. Despite achieving a similar structural state after HPT, the deformation temperatures used has different effects on the mechanical and functional properties of the steel. After HPT at 20 °C, the yield strength of the 316L steel increased by more than nine times up to 1890 MPa, and the fatigue limit by more than two times up to 550 MPa, when compared to its coarse-grained counter-parts. After HPT at 20 °C, the 316LVM steel exhibited better ductility, higher low-cycle fatigue resistance, greater resistance to corrosion, and improved in vitro biocompatibility compared to processing at 400 °C. The reasons for the deterioration of the properties after HPT at 400 °C are discussed in the article.

Effect of high pressure torsion on interfaces and mechanical properties of SiC/Al composite

Powder mixture of pure Al and oxidized SiC was consolidated into 10 wt% SiCP/Al composite by high pressure torsion at 473 K with the torsion numbers of 1, 4 and 8. The SiC–Al interfaces evolutions and Al matrix were studied by transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), the valence of elements was detected by X-ray photoelectron spectroscopy (XPS). The results show three different interfaces in the HPT-processed samples, namely the SiO2–Al interface, SiO2–Al2O3 interface and SiC–Al2O3 interface. Elements inter-diffusion occurred at both of these three interfaces, but the solid-state atomic reaction 3SiO2+Al→Al2O3+3Si only can be characteristic at the original SiO2–Al interface. High-density dislocation and Al2O3 layer increase the element diffusion distance. After 8 turns HPT process, the SiC particles remained in the fracture of 8 turns HPT sample is the least. The relative density and mechanical properties (Vickers hardness, tensile strength and elongation) are the best compared to 1 and 4 turns sample which imply the desirable interface bonding between 1, 4 and 8 HPT turns.

Effect of high-pressure torsion on first hydrogenation of Laves phase Ti0.5Zr0.5(Mn1-xFex)Cr1 (x = 0, 0.2 and 0.4) high entropy alloys

Laves phase high-entropy alloys are considered as good candidates for hydrogen storage applications. However, they usually suffer from poor first hydrogenation kinetics, the so-called activation process. In this paper, we attempt to solve the activation problem of the Ti0.5Zr0.5(Mn1-xFex)Cr1 (x = 0, 0.2 and 0.4) by high-pressure torsion (HPT). The HPT process was carried out under 6 GPa pressure for 5 revolutions in air on samples synthesized by arc melting. The hydrogenation kinetics were measured using a Sievert’s type apparatus at room temperature under 2 MPa of hydrogen pressure. While the as-cast alloys become totally inert to hydrogen after air exposure, the HPT-processed samples absorb 1.6–1.8 wt% of hydrogen at room temperature in a few seconds even after air exposure for 2 months. The easy activation of alloys processed by HPT is due to the formation of lattice defects that act as nucleation points. These results confirm that HPT processing is an effective strategy to develop active hydrogen storage materials.

The effect of high-pressure torsion on irradiation hardening of Eurofer-97

The effect of high-pressure torsion on irradiation hardening of Eurofer-97

Simultaneous enhancement of strength and ductility in nonflammable Mg alloys through dynamic precipitation using severe plastic deformation under high pressure

This study focuses on the effect of high-pressure torsion (HPT) on the microstructure, mechanical properties, electrical conductivity and ignition temperature of a Mg–6Al–3Ca-0.02Mn-0.008Be (at%) alloy. The HPT-processed samples exhibit high tensile yield strengths of 400 MPa with total elongations of ∼5%. Quantitative evaluation shows that the high tensile strength is attributed to the ultrafine grain refinement, the generation of high dislocation density and the fragmentation of intermetallic particles to nanoscales. Dynamic precipitation of nanosized particles during the HPT processing at elevated temperature might have also contributed to the high strengthening. It is shown that homogeneous grain refinement throughout the sample leads to the simultaneous enhancement of strength and ductility. The electrical conductivity is restored due to concomitant precipitation during the HPT processing at 573 K. There is no appreciable difference in the ignition temperature between before and after the HPT processing.

The Effect of High-Pressure Torsion on the Structure and Mechanical Properties of the Al–Ca–Cu Alloy

The Effect of High-Pressure Torsion on the Structure and Mechanical Properties of the Al–Ca–Cu Alloy

Comparative analysis of the aging kinetics in low-alloyed Cu – Cr – Hf and Cu – Cr – Zr alloys after high pressure torsion

The kinetics of phase precipitation during aging in the Cu – Cr – Hf and Cu – Cr – Zr alloys after high pressure torsion (HPT) has been studied and compared with quenching state. The effect of HPT on the kinetics of aging was revealed by the differential scanning calorimetry (DSC) and confirmed by changes in the microhardness and electrical resistivity. Analysis of the microstructure and phase precipitation after HPT and subsequent aging using a transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) revealed three types of phases in each of the alloys: Cu matrix, chromium and zirconium- or hafnium-rich phases. By measuring the microhardness, a higher degree hardening after HPT and subsequent aging was revealed in the Cu – Cr – Hf alloy compared to the Cu – Cr – Zr alloy.

Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy.

The Ti-18Zr-15Nb shape memory alloys are a new material for medical implants. The regularities of phase transformations during heating of this alloy in the coarse-grained quenched state and the nanostructured state after high-pressure torsion have been studied. The specimens in quenched state (Q) and HPT state were annealed at 300-550 °C for 0.5, 3, and 12 h. The α-phase formation in Ti-18Zr-15Nb alloy occurs by C-shaped kinetics with a pronounced peak near 400-450 °C for Q state and near 350-450 °C for HPT state, and stops or slows down at higher and lower annealing temperatures. The formation of a nanostructured state in the Ti-18Zr-15Nb alloy as a result of HPT suppresses the β→ω phase transformation during low-temperature annealing (300-350 °C), but activates the β→α phase transformation. In the Q-state the α-phase during annealing at 450-500 °C is formed in the form of plates with a length of tens of microns. The α-phase formed during annealing of nanostructured specimens has the appearance of nanosized particle-grains of predominantly equiaxed shape, distributed between the nanograins of β-phase. The changes in microhardness during annealing of Q-specimens correlate with changes in phase composition during aging.

Effect of High Pressure Torsion on Microstructure and Properties of Intermetallic Containing CoCrFeNi2.1Nb0.2 High Entropy Alloy: Comparative Insights

Effect of High Pressure Torsion on Microstructure and Properties of Intermetallic Containing CoCrFeNi2.1Nb0.2 High Entropy Alloy: Comparative Insights

EFFECT OF HIGH-PRESSURE TORSION ON MICROSTRUCTURE CHANGES IN MICROALLOYED STEEL

Тhe most common method of manufacturing parts is metal pressure treatment, as a result of which the entire reserve of strength and ductility of the material is not exhausted. Therefore, the issues of the influence of plastic deformation on the cyclic durability and endurance limits of steel rings are relevant. In this article experimental studies of the effect of high pressure torsion in a die of new design on the evolution of the microstructure and the change of mechanical properties have been carried out. As a result, the fundamental possibility and efficiency of using the proposed method for the formation of ultrafine grained structure and increasing the strength properties of steel rings has been proved. Strain was carried out at ambient temperature in six passes. The strain resulted in an ultrafine-grained structure with an average grain size of 0.5 μm and a great number of large-angle boundaries. The strength properties of microalloyed steel increased almost threefold compared to the initial state, the microhardness also increased threefold, i.e. increased from 760 MPa in the initial state to 1935 MPa after strain. The greatest increase in strength properties occurred in the first 3 cycles of strain.

Structure, Biodegradation, and In Vitro Bioactivity of Zn-1%Mg Alloy Strengthened by High-Pressure Torsion.

The effect of high-pressure torsion (HPT) on the microstructure, phase composition, mechanical characteristics, degradation rate, and bioactive properties of the Zn-1%Mg alloy is studied. An ultrafine-grained (UFG) structure with an average grain size of α-Zn equal to 890 ± 26 nm and grains and subgrains of the Mg2Zn11 and MgZn2 phases with a size of 50-100 nm are formed after HPT. This UFG structure leads to an increase in the ultimate tensile strength of the alloy by ~3 times with an increase in elongation to 6.3 ± 3.3% due to the formation of a basal texture. The study of corrosion resistance did not show a significant effect of HPT on the degradation rate of the alloy. In addition, no significant changes in the bioactivity of the alloy after HPT: hemolysis, cellular colonization and Escherichia coli growth inhibition.

Effect of High-Pressure Torsion on the Microstructure and Magnetic Properties of Nanocrystalline CoCrFeNiGax (x = 0.5, 1.0) High Entropy Alloys.

In our search for an optimum soft magnet with excellent mechanical properties which can be used in applications centered around “electro mobility”, nanocrystalline CoCrFeNiGax (x = 0.5, 1.0) bulk high entropy alloys (HEA) were successfully produced by spark plasma sintering (SPS) at 1073 K of HEA powders produced by high energy ball milling (HEBM). SPS of non-equiatomic CoCrFeNiGa0.5 particles results in the formation of a single-phase fcc bulk HEA, while for the equiatomic CoCrFeNiGa composition a mixture of bcc and fcc phases was found. For both compositions SEM/EDX analysis showed a predominant uniform distribution of the elements with only a small number of Cr-rich precipitates. High pressure torsion (HPT) of the bulk samples led to an increased homogeneity and a grain refinement: i.e., the crystallite size of the single fcc phase of CoCrFeNiGa0.5 decreased by a factor of 3; the crystallite size of the bcc and fcc phases of CoCrFeNiGa—by a factor of 4 and 10, respectively. The lattice strains substantially increased by nearly the same extent. After HPT the saturation magnetization (Ms) of the fcc phase of CoCrFeNiGa0.5 and its Curie temperature increased by 17% (up to 35 Am2/kg) and 31.5% (from 95 K to 125 K), respectively, whereas the coercivity decreased by a factor of 6. The overall Ms of the equiatomic CoCrFeNiGa decreased by 34% and 55% at 10 K and 300 K, respectively. At the same time the coercivity of CoCrFeNiGa increased by 50%. The HPT treatment of SPS-consolidated HEAs increased the Vickers hardness (Hv) by a factor of two (up to 5.632 ± 0.188) only for the non-equiatomic CoCrFeNiGa0.5, while for the equiatomic composition, the Hv remained unchanged (6.343–6.425 GPa).

Effect of high-pressure torsion on high cycle fatigue of commercially pure Cu: Some insights from formation of surface micro-cracks

In most technical applications, fatigue is related to highly localized load distributions. While high-pressure torsion (HPT) materials cannot prevent crack initiation, they promise to improve the resistance to crack nucleation and propagation. Herein, commercially pure Cu was processed through HPT at a pressure of 6 GPa up to 50 turns. Small “cantilever” type samples were fabricated from annealed and HPT samples. The cantilever samples were subjected to fully-reversed cyclic bending. The maximum stress amplitude was chosen to reach the high cycle fatigue regime, and the experiments were stopped when the resonant frequency decayed by 20%. Compared to the annealed samples, the HPT samples showed higher lifetimes. The grain size in the HPT samples remained stable during fatigue, and dislocation substructures, a stacking of parallel dislocations, could be observed in all samples. In HPT samples, the area fraction of surface micro-cracks increased with the local stress amplitude. This can be attributed to the inhibition of crack nucleation at low stresses due to the high strength of HPT samples and the crack arrest at the boundaries of their ultra-fine grains. The obtained insights into the microstructure-fatigue response relationship are vital for understanding the initial stages of fatigue failure in ultra-fine-grained materials and their technological adoption for applications in extreme environments.

Evaluation of texture weakening and microstructural evolution in an Fe–10Ni–7Mn martensitic steel severely deformed by six turns of high-pressure torsion

The effect of high-pressure torsion (HPT) on textural components and microstructural evolution of an Fe–10Ni–7Mn steel was investigated. Six turns of HPT, with a rotation rate of 1 rpm and with a pressure of 6.0 GPa, were applied to a solution annealed steel. Microstructural and textural evolution, including dislocation characteristics and grain size/misorientation measurements, were accomplished using electron backscatter diffraction (EBSD). The results showed that a fully martensitic structure, containing a high density of dislocations, was developed during the solution annealing stage and subsequently the application of six turns of HPT process converted the low-angle grain boundaries (LAGBs) of the solution annealed condition into high-angle grain boundaries (HAGBs). Thus, the sub-grain boundaries established in the solution annealed condition were altered into very sharp HAGBs. The grain size was also decreased from ∼ 25 μm in the solution annealed situation to ∼210 nm in the severely deformed condition of six-turn high-pressure torsion state. Yield strength, and tensile strength were increased from 765 MPa, and 840 MPa in the solution annealed case to 1890 MPa, and 2230 MPa in the six-turn HPT-processed sample, respectively. Under such a condition, ductility was decreased from 15.2% to 6.1% in the severely deformed state. Applying six turns of HPT developed a predominantly {111}//ND texture. However, the overall texture intensity of the HPT-processed sample was weakened to a value of about one-quarter of the as-quenched solution treated sample. This was related to dynamic recrystallization and grain subdivision as well as a dislocation density reduction in the HPT-processed sample. The texture components of strong Copper ({112}<111>), S ({123}<634>) and some average intensity Cube {100}<0001> were observed in the {100} pole figure in the solution annealed condition. As well, γ-fibre (<111>//ND) and β-fibre were seen in this condition. However, {110}<uvw> fibres were mostly developed in the six-turn sample with the texture components of E1{011‾}<111>, E2{01‾1}<111>, J1{01‾1}<2‾11>, J2+{11‾0}<1‾1‾2>, D2{1‾1‾2}<111> , D1{112‾}<111> and F {110}<001>. In addition, the Cu{112}⟨111⟩ component was significantly diminished. This weakened Cu{112}⟨111⟩ component would have caused enhancement of the mechanical properties, particularly the formability and toughness, as previously reported by the current authors. Finally, it was found that applying severe plastic deformation (SPD) in the form of HPT reduces the effect of martensitic texture in the solution treated steel.