Increase In Degree Of Deformation Research Articles

Origins and optimization mechanisms of periodic microstructures in Al-Cu alloys fabricated by wire arc additive manufacturing combined with Interlayer Friction Stir Processing

Inter-layer Friction Stir Processing on Arc Additive Manufactured Components offers significant potential for performance enhancement, yet the homogenization of microstructures has become a challenge for industrial application. To address this, 2319 Al-Cu alloy components were fabricated through the Wire Arc Additive Manufacturing + Interlayer Friction Stir Processing (WAAM-IFSP)1 technique, and a systematic study was conducted on the effects of deformation degree, deformation temperature, and strain rate changes on the microstructural evolution, revealing three distinct periodic microstructures. An increase in deformation degree resulted in a uniform periodic microstructure, attributed to the more uniform internal deformation caused by the increased deformation degree. At a deformation degree of 24.1 %, higher strength and ductility were achieved, along with a notable bimodal grain structure (BGS). Further research indicated that this structure would distribute more widely within the matrix with increasing strain rate, aiding in further performance breakthroughs, ultimately reaching an ultimate tensile strength (UTS) of 404 MPa and an elongation (EL) of 32 %. However, imperfections in the process led to inhomogeneity in the structure. Focusing on the dynamic recrystallization (DRX) mechanisms during stirring can improve this phenomenon. The research revealed that the fine grains in the BGS were controlled by a synergy of dominant discontinuous dynamic recrystallization (DDRX) and auxiliary continuous dynamic recrystallization (CDRX) nucleation mechanisms. The findings are expected to provide a theoretical basis for the optimization of WAAM-IFSP processes and microstructural and performance regulation, which is crucial for enhancing the industrial application prospects of aluminum alloys.

Effect of deformation degree on the mechanical properties of Al-Zn-Mg-Cu alloys: an industrial study

Abstract Hot deformation is a crucial process in the manufacturing of aluminum alloy products, as its parameters exert a profound influence on the ultimate properties of the alloys. This work reports on the Al-Zn-Mg-Cu alloys at a deformation temperature of 450°C, a deformation rate of 5 mm/s, and deformation degrees of 50% and 90% in industrial settings. Following that, an extensive assessment of the alloys’ mechanical characteristics, including their fracture toughness, tensile strength, and fatigue performance. Furthermore, a quantitative analysis of the microstructure was undertaken using OM and EBSD, which revealed that both the average and sub-grain sizes of the two alloys exhibited comparable characteristics. However, the recrystallization fraction showed a difference, with the alloy deformed to 90% exhibiting a higher fraction than the alloy deformed to 50%, while these recrystallized grains are distributed in chains. With the increase of deformation degree from 50% to 90%, the yield and ultimate strengths increase slightly. The opposite law is demonstrated by fatigue crack propagation resistance and fracture toughness. Put otherwise, compared to the alloy deformed to 50%, the alloy deformed to 90% exhibited a faster rate of fatigue crack propagation and a lower fracture toughness. In summary, this research examines how the degree of deformation affects the mechanical characteristics and microstructure of Al-Zn-Mg-Cu alloys.

Mechanical and electrical properties of two-dimensional BN doped with carbon group elements: first-principles calculations

Abstract Research of low-dimensional nanomaterials provides a direction for solving the problems of energy and environmental pollution. In this work, the regulation mechanism of doping carbon group elements X (X = C, Si, Ge, Pb, Sn) on mechanical and electrical properties of 2D monolayer BN are investigated by first-principles calculations. Two doping sites were selected, replace B atoms (B15N16X) or N atoms (B16N15X). Lower relative enthalpies and the elastic constants, which conforming to the mechanical stability standard, fully prove the stability of the doping system. Compared with B15N16X, B16N15X has larger structural distortion, smaller elastic constants and modulus, and is more inclined to ductility. With the increase of atomic radius, the deformation degree increases and the elastic parameters decrease. C-doped by replacing B atoms improves the elastic mechanical properties of monolayer BN. Sn-doped and Pb-doped modulate the monolayer BN into ductility. More importantly, all doped configurations exhibit magnetism. The indirect band gap of the undoped system can also be modulated into a direct band gap, B15N16C, B16N15Si and B16N15Ge all have direct band gaps in the spin-down direction. Asymmetric impurity energy levels DOS further verify the magnetism of the reference system.

Severe plastic cold rolling effects in nickel–vanadium alloy: Microstructure, texture evolution and mechanical properties

The microstructural characteristics and morphological attributes of the target material, along with its intrinsic properties, can significantly influence the performance of the resultant film. Currently, commercially available nickel-vanadium targets employed in the industry have not been subjected to investigations aimed at controlling grain size and grain orientation. This study examines the effects of unidirectional rolling at room temperature, combined with substantial deformation, on the alterations in microstructure, texture evolution, and mechanical properties of the NiV7 alloy. The process of severe plastic cold rolling leads to a continuous elongation and refinement of the grains. The changes in microstructure and texture of the cold-rolled sheets were analyzed using electron backscatter diffraction (EBSD) technology. At an 80% reduction, a significant number of sub-grains are observed, which transform into deformed grains as the reduction reaches 95%. With a thickness reduction of 96.6%, the average grain size is approximately 1.10 μm. Further increases in reduction do not lead to significant alterations in the grain structure; instead, the grain orientation progressively becomes more uniform with higher levels of deformation. The combination of substantial deformation and lower rolling rates results in an increased number of high-angle grain boundaries. The alloy displays various textures throughout the rolling process, including S-type, copper-type, brass-type, fiber, and cubic textures. Notably, the prevalence of S-type and fiber textures diminishes as the degree of deformation increases, while the cubic texture becomes increasingly prominent. Upon achieving a reduction of 95%, the cubic texture emerges as the dominant texture. A transmission electron microscope (TEM) was utilized to examine the extensive array of dislocations, dislocation cells, dislocation walls, and shear bands generated during the cold rolling process. At a deformation level of 96.6%, the ultimate tensile strength of the alloy demonstrates a significant enhancement, attributed to mechanisms of dislocation strengthening and grain strengthening, reaching a value of 1231 ± 20 MPa, accompanied by a post-fracture elongation of approximately 2%. The ultimate tensile strength exhibited an increase of 781 ± 20 MPa compared to the sample prior to the rolling process; however, there was a notable reduction in plasticity.

Effect of Tectonic Deformation on the Pore System and Methane Adsorption of Anthracite Coal.

Tectonic deformation significantly alters the physical structure of coals, holding great importance to the coal mining industry and coalbed methane. In this study, eight anthracite coal samples with varying degrees of deformation were collected to investigate the effects of tectonic deformation on the pore system and CH4 adsorption of anthracite coals. In addition, low-temperature gas adsorption (N2 and CO2), Raman spectroscopy, and CH4 isothermal experiments were performed. The results revealed that coal samples with higher degrees of deformation exhibited larger ratios of D-band intensity to G-band intensity (I D/I G), indicating increased molecular defects induced by tectonic deformation. As the deformation degree of the coal samples increased, the mesopore volume increased from 0.00044 cm3/g (primary coal) to 0.0019 cm3/g (scaly coal). Conversely, the micropore volume tended to decrease with the increasing deformation degree of the coal samples. Moreover, the impact of deformation degree on the CH4 adsorption capacity of anthracite coals was complex. With the deformation degree increasing, the Langmuir volume initially decreased from 32.0 to 24.55 cm3/g and then rose to 30.14 cm3/g. This complexity arose from the differential effects of tectonic deformation on various pore types, where micropores and mesopores collectively determined the CH4 adsorption capacity of anthracite coals. This study analyzed the influence of tectonic deformation on the pore structure and CH4 adsorption capacity at the molecular level, providing valuable insights for evaluating the in situ CH4 content in anthracite coal seams.

Effects of strain induced martensite on high temperature electrochemical performance of 321 stainless steel in the simulated PWR first circuit environment

The electrochemical properties of 321 stainless steel with different cold strains in simulated PWR first circuit environment were studied mainly by electrochemical impedance spectroscopy (EIS). The results show that with the increase of strain (0, 20%), the charge transfer resistance increases and the film resistance decreases. By combining the electrochemical experiments and microscopic characterization results of different specimens, including solution annealed, cold worked and hot worked, it is found that the charge transfer resistance increases with the increase of deformation degree, the increase of strain induced martensite content enriches Cr in the oxide layer, but with the decreased material corrosion resistance.

Regularities of formation of microstructure and mechanical properties of copper m1 under combined plastic deformation

The influence of combined plastic deformation, including methods of intense plastic deformation and traditional metal forming, on the structure and mechanical properties of M1 copper was studied. It has been shown that combined processing helps to increase the dimensional uniformity of hardness across the cross-section of the workpiece and contributes to the refinement of microstructure elements. Thus, with an increase in the equivalent degree of deformation, the level of mechanical properties of M1 copper increases accordingly.

Influence of deformation degree on grains size and borders between them in metal alloys during cold rolling of sheets

The internal structure of metal products was investigated and it was identified that it affects quality and workability of equipment parts. Changes that occur in metal products structure during cold treatment by pressure, which lead to changes in physical and mechanical properties of products, have been analyzed. It was established that grains and borders between them, which determine internal structure of metal products, change their shape and size during cold rolling, depending on percentage reduction value. It is offered to consider grain borders as amorphous layer. Methodology has been developed to study influence of deformation degree during cold rolling to grain size of metal internal structure and intergranular layer volume. Intergranular surface area, its volume and part of surface volume from metal volume were determined. Parameters of internal structure of low-carbon steel were calculated depending on reduction value during cold rolling. According to study results, interconnection between grains size and deformation degree was established; and percentage reduction influence to grain size and borders between them was determined, obtaining a minimum standard grain size with percentage reduction of over 80 %; yield strength and its growth for metal alloy during cold rolling are established, which allows controlling the strength of steel by adjusting the grain size and their junction surface. It is shown that with an increase in deformation degree, yield strength of metal product material increases in hyperbolic dependence, and fraction of amorphous layer and strength properties of low-carbon steel change almost equally in exponential functions. It is revealed that during cold rolling, it is possible to control internal properties of obtained product by adjusting reduction value.

Development of temperature-speed modes of hot deformation of Co – 28Cr – 6Mo alloy based on processing maps

In the article, the tests of the medical alloy Co – 28Cr – 6Mo after homogenization for uniaxial compression at temperatures of 1000, 1100 and 1200 °C and strain rates of 1, 10, and 50 s­–1 were carried out using the Gleeble System 3800. The stress-strain curves describing the alloy deformation behavior were obtained. The calculations of hot deformation parameters (activation energy, Zener-Hollomon parameter) were performed using three models (power-law, exponential, and hyperbolic sine function) describing the flow stress. The highest degree of convergence was shown by the calculation results based on the power function and the hyperbolic sine function. These models can be used to accurately calculate the flow stress at given temperature and strain rate parameters, or to simulate the deformation process. Also, based on processing maps, the authors developed the deformation-speed modes of hot deformation of the Co – 28Cr – 6Mo alloy. It will make it possible to choose the optimal rolling modes in the future. According to the data obtained, favorable temperature-speed conditions for hot deformation are shifted as deformation accumulates to the region of high temperatures and low strain rates. At the same time, the extremely unfavorable zone with negative values of the ξ-criterion, which appears at e = 0.3 – 0.4, continues to grow quite significantly with an increase in the deformation effect. Hot deformation of the Co – 28Cr – 6Mo alloy at low compression ratios (e < 0.2) is more expedient to perform at temperatures above 1150 °C and strain rates of at least 20 s–1. With an increase in deformation degree, it is necessary to choose lower strain rates (1 – 5 s–1) and higher deformation temperature.

Structural Phase Transformation of Rail Steel in Compression

The analysis of structure and defective substructure of rail steel in uniaxial compression to a degree of 50% is carried out. It is revealed that cold hardening has a multi-stage character and is accompanied by fragmentations of pearlite grains which is in field as the degree of deformation increases and reaches ≈ 0.4 volume of the foil studied at ε = 50%. The fragments being formed in ferrite plates are separated by low-angle boundaries. The average size of the fragmented ferrite decreases from 240 nm at ε = 15% to 200 nm at ε = 50%. Concurrently with the ferrite fragmentation, fragments of cementite are also observed. It is found that the sizes of the cementite fragments are in a range of 15 to 20 nm and depend weakly on the degree of sample deformation. The cementite fragmentation is caused by deformation-induced carbon dissolution and dislocation-induced fracture. The carbon atoms diffuse from cementite crystal to dislocations, which move through an interplanar space to form particles of tertiary cementite at nanoscale (2–4 nm). It is found that the increase in the degree of deformation is accompanied by a decrease in the scalar and an excess dislocation density. A physical interpretation of the observations has been given.

Evolution of structure of rail steel lamellar pearlite under compression deformation

The article presents the results of analysis of evolution of the defective substructure of rail steel pearlite with lamellar morphology under deformation by uniaxial compression. The strain hardening of the studied steel under such deformation has a multistage character. Deformation of steel is accompanied by fragmentation of pearlite grains, which intensifies as the degree of deformation increases and reaches 0.4 of the studied foil volume at ε = 50 %. Fragments formed in ferrite plates are separated by low-angle boundaries. It was established that the average sizes of ferrite plate fragments decrease from 240 nm (ε = 15 %) to 200 nm (ε = 50 %) with an increase in the deformation degree. Fragmentation of cementite plates was revealed. It was found that the size of the fragments varies within 15 – 20 nm and weakly depends on the degree of steel deformation. Fracture of cementite lamellae, proceeding by their dissolution and cutting by mobile dislocations, was discovered. Carbon atoms that have passed from the crystal lattice of cementite to dislocations are carried out into the interlamellar space and form particles of tertiary cementite, the size of which is 2 – 4 nm. In the process of steel deformation, an inhomogeneous dislocation substructure is formed, which is due to the deceleration of dislocations by cementite particles. It was found that an increase in the deformation degree is accompanied by a decrease in the scalar and excess density of dislocations, which may be due to the escape of dislocations into low-angle boundaries, as well as their annihilation. It was established that the sources of internal stress fields are the interfaces between pearlite grains and colonies, cementite plates in pearlite grains, particles of the second phase located in the volume of ferrite plates.

Deformation behavior, microstructure evolution, and dynamic recrystallization mechanism of an AZ31 Mg alloy under high-throughput gradient thermal compression

A high-throughput gradient thermal compression process was adopted to investigate the effects of thermal deformation parameters on the deformation behavior and microstructure evolution of a rolled AZ31 Mg alloy. The results showed that with increasing deformation degree, the flow stress-strain curves of the double-cone samples compressed along the normal direction (ND), transverse direction (TD), and rolling direction (RD) of rolled Mg alloy rapidly reached their peak value, then decreased gradually, and finally maintained a trend of horizontal change. Under the same strain condition, the dynamic recrystallization (DRX) degree of the double-cone sample increased gradually with increased deformation temperature. Twins were more likely to occur when compression occurred in the TD and RD, rather than along ND. With increasing temperature or strain, the number of twins that formed during compression gradually decreased. At deformation temperatures of 250 °C and 300 °C, continuous dynamic recrystallization was the main DRX mechanism in the double-cone samples compressed along the ND, TD, and RD. Furthermore, the twin-assisted DRX mechanism also occurred in the double-cone samples compressed at 250 °C along the TD and RD. During compression at 350 °C and 400 °C along the ND, TD, and RD, discontinuous dynamic recrystallization occurred in the double-cone samples, indicating that the DRX mechanism changed with increasing compression temperature.

Comparison of Nanopore Structure Evolution in Vitrinite and Inertinite of Tectonically Deformed Coals: A Case Study in the Wutongzhuang Coal Mine of Hebei Province, North China

The understanding of the nanopore structure in tectonically deformed coal (TDC) could be expanded from the perspective of a single maceral. A total of 10 TDCs with an increasing deformation degree (in the order of unaltered, cataclastic, porphyroclast, scaly, and powdery coal), were collected in a single coal seam and stripped into 10 vitrinite and 10 inertinite samples. Carbon dioxide (CO2) adsorption and nitrogen (N2) adsorption/desorption experiments were conducted to reveal the nanopore structure, whereas 13C solid-state nuclear magnetic resonance and X-ray diffraction experiments were conducted to detect the macromolecular structure. The results reveal that the macromolecular structures of both vitrinite and inertinite can be altered by tectonic stress. As the deformation degree increases, the aliphatic carbons decrease, the aromatic carbons increase, and the aromatic interlayer spacing decreases, whereas the crystallite stacking height and the average number of crystallites in a stack increase. For mesopores, the pore volume of vitrinite slowly decreases and then increases at the stage of scaly coal, whereas that of inertinite fluctuates with no obvious regularities. For micropores, the pore volume of vitrinite deceases as the deformation degree increases, whereas that of inertinite decreases since the deformation stage of porphyroclast coal, and little changed from the deformation stage of unaltered to cataclastic coal. As the coal deformation degree increases, the aromatic interlayer spacing decreases, resulting in a decrease in the micropore volume; however, the average crystallite stacking height and the average number of crystallites in a stack increase, leading to an increase in the micropore volume. Therefore, the micropore decreases and then increases as the coal deformation degree increases. However, the macromolecular changes weakly affect the mesopore evolution in the coal deformation process.

Alternate Thermomechanical Heat Treatment Cycles for the Enhancement in Hardness and Tensile Properties of Commercial Grade AA6061

Numerous research incorporating precipitation hardening and/or strain hardening on Al-Mg-Si alloys has demonstrated improved mechanical properties in the alloys. However, there is a lack of research on how these processes can be combined efficiently to provide better strength and hardness for the alloys. The present study describes the effects of low temperature thermomechanical treatment (LTMT - combination of conventional age hardening and strain/work hardening) carried at two isothermal aging temperatures on the hardness and strength of the aluminium alloy 6061 (AA6061). Further, an innovative LTMT process is also proposed, which aims at further enhancing the mechanical properties of the alloy. The study revealed the increase in degree of deformation improved the strength and hardness of the alloy with reduced aging time. The effect of the degree of deformation, pre-deformation, and alternate deformation and aging cycles on the hardness and strength of the alloy was studied with the help of fracture surface analysis.

Carbide-facilitated nanocrystallization of martensitic laths and carbide deformation in AISI 420 stainless steel during laser shock peening

Severe plastic deformation (SPD) techniques such as laser shock peening (LSP) have been widely adopted to modify microstructure of materials. Understanding the plastic deformation mechanisms during SPD will enable the optimization of SPD process to obtain desired microstructures. Using LSP technique, we modified surface microstructure of AISI 420 martensitic stainless steel containing both martensitic lath and carbide, and investigated deformation mechanisms based on microstructural evolution. High-resolution transmission electron microscopy and X-ray diffraction results revealed that the laser shock wave induced severe deformation in the original sub-micron carbide, resulting in carbide fragmentation in AISI 420 martensitic stainless steel. These LSP-induced carbide fragments and original carbides promote nanocrystallization of martensitic laths, because the carbide/matrix interface acts as an effective dislocation nucleation sites and an obstacle to the dislocation movement. The LSP-generated martensitic lath nanocrystallization is rationalized by two simultaneous subdivision modes: the intersection between longitudinal and transverse sub-boundaries developed from dense dislocation walls and transverse sub-boundaries transformed from dislocation tangles. In addition, the carbide decomposition happened simultaneously with severe plastic deformation, which was reflected by the decreasing continuous Cr concentration and the increment of Fe concentration with increasing deformation degree in the deformed carbide. Finally, fine grain strengthening, precipitation strengthening and dislocation strengthening induced by LSP contribute to an increase in the strength and ductility of AISI 420 martensitic stainless steel.

Complex Structural Effects in Deformed High-Manganese Steel.

The research presented in this paper is part of a larger project concerning deformation behavior, microstructure and mechanical properties of high-manganese steels with different chemical compositions and processed under various conditions. The current investigation deals with the development of microstructure and crystallographic texture of Fe-21.2Mn-2.73Al-2.99Si steel deformed in tension until fracture at ambient temperature. The deformation process of the examined steel turned out to be complex and included not only dislocation slip and twinning but also strain induced phase transformations (γ → ε) and (γ → α′). The formation of ε-martensite with hexagonal structure was observed within the microstructure of the steel starting from the range of lower strains. With increasing deformation degree, the α′-martensite showing a cubic structure gradually began to form. Attempts have been made to explain the circumstances or conditions for the occurrence of the deformation mechanisms mentioned above and their impact on the mechanical properties. The obtained results indicate that the strength and plastic properties of the steel substantially exceed those of plain carbon steels. Since both, mechanical twinning and the strain-induced phase transformations took place during deformation, it seems that both types of deformation mechanisms contributed to an increase in the mechanical properties of the examined manganese steel.

Microstructure and crystallographic texture of Cu-Zn alloys subjected to ECAP and flat rolling

This paper presents the results of the microstructure and crystallographic texture investigations of the Cu-Zn alloys system with different stacking fault energies (SFE) subjected to severe plastic deformation (SPD) by equal channel angular pressing (ECAP) and subsequent flat rolling. It is shown that ECAP leads to the formation of an ultrafine-grained (UFG) structure. Further flat rolling is accompanied by a decrease in the size of structural elements and the formation of nanoscale twins, which are more likely to be detected in an alloy with a lower SFE. As the deformation degree increases, the main crystallographic textures components of the investigated alloys become Brass and Goss components.

Improving ductility of AlSi7Mg alloy by casting-forging process: effect of deformation degree

To improve its ductility and clarify the mechanism, the AlSi7Mg alloy fabricated by a novel casting-forging process was solid-soluted at 535 °C for 5 h, followed by aging at 170 °C for 2 h. Phase component, microstructure were observed and mechanical properties were tested. The results show that the alloy contains Al, Si and Al–Si intermetallics. The eutectic Si particles present equiaxed and the Al–Si precipitations present filamentous morphorgy in the alloy. The eutectic Si particles present quasi-continuous network distribution, dividing the matrix into equiaxed units. When the deformation degree increased from 15% to 35%, the units are refined and the precipitation of Al–Si intermetallics is prevented. The difference of ultimate strength between surface and center was decreased, while the elongation improved obviously with the increase of deformation degree. The most excellent elongation reached 12% when the deformation degree was 35%, with the improvement of 7%. The improvement of ductility is owed to the fine, equiaxed eutectic Si particles, the refined units and the prevented precipitations.

Simulated synthesis of silica nanowires by lyotropic liquid crystal template method

ABSTRACT Dissipative particle dynamics simulations were adopted to study the mechanism of lyotropic liquid crystal (LLC) formation and the synthesis process of silica nanowires by LLC template method. Simulation results show that the one-dimensional (1D) LLC channel can be formed at the Pluronic F127 concentration range of 61 ∼ 67%. With the increase of Pluronic F127 concentration, the diameter of LLC channel decreases and the deformation degree increases. The effect of PEO: PPO ratio on the diameter of LLC channel is slight. The appropriate PEO: PPO ratio of Pluronic is 40:70 for the formation of 1D LLC channel, as the deformation degree of channel is the smallest in this case. The effect of polymerisation degree on the diameter and deformation degree of LLC channel is both little. With the increase of TEOS concentration, the nanowire diameter increases rapidly at first, and then increases quite slowly. This work can provide guidance for silica nanowires synthesis by LLC template method.

Fe/Ni diffusion behavior in the shear-extrusion solid state bonding process

• A diffusion layer about 3 μm thick can be formed through Fe/Ni interdiffusion during the SEB process. • The main composition of the diffusion layer is Fe-Ni substitutional solid solution distributed in Ni base. • The maximum actual interdiffusion coefficient of Fe/Ni atoms can achieve 5.4 × 10 −13 cm 2 /s during the SEB process. • Relative diffusion layer thickness increases with the increase of deformation degree with a linear relationship. The shear-extrusion bonding (SEB) of pure iron (99.9 %) and pure nickel (99.5 %) are carried out under the experiment condition of heating temperature 1050℃, top die speed 12 mm/s with different deformation degrees. The Fe/Ni diffusion behavior is analyzed through experimental studies and theoretical analysis. The results indicate that a diffusion layer about 3 μm thick is formed through Fe/Ni interdiffusion and the main compositions of the diffusion layer are Ni and Fe-Ni solid solution. It is found a large number of vacant clusters are formed at the Fe/Ni interface in the SEB process. The diffusion of matrix atoms or substitutional solute atoms is mainly realized by vacancies, so the diffusion mechanism of Fe/Ni in SEB process is vacancy diffusion mechanism or vacancy pair diffusion mechanism. The actual interdiffusion coefficient of Fe/Ni in SEB process is 100∼1000 times higher than the interdiffusion coefficient of Fe/Ni atoms under thermal action. So the plastic deformation provides additional vacancies to promote the formation of diffusion layer. The relative diffusion layer thickness increases from 6.02 μm to 12.01 μm when the deformation degree increases from 50 % to 74.2 %, and the relative diffusion layer thickness increases linearly with the increase of deformation degree.