Temperature Conditions Of Deformation Research Articles

Deformation mechanism and hardening behavior of gradient heterostructured magnesium alloys prepared by severe shear deformation

Lightweight equipment in aerospace and other fields urgently requires magnesium (Mg) alloys components with high-strength plasticity. For this reason, in this study, a gradient heterogeneous structure containing nanocrystallines was constructed successfully using a severe shear deformation process that combines severe plastic deformation techniques and torsional deformation characteristics. The evolution of the microstructure and hardness of Mg-12.12Gd-4.2Y-2.28Zn-0.36Zr (wt%) alloys prepared by severe shear deformation with changes in deformation temperature were investigated. The gradient heterogeneous structure of the alloys formed naturally under high hydrostatic pressure and severe shear stress, and its thickness increased with the deformation temperature. With the application of shear stress, a large amount of rotational dynamic recrystallization (RDRX) behavior occurs in the alloys, refining the coarse initial grains (∼126.3 µm) into fine grains (∼2.03 µm) or even ultrafine grains (∼1 µm). During the RDRX process, low angle grain boundaries (LAGBs) began to form at high distorted grain boundaries and unique lamellar structures, followed by a rapid expansion into the interior of the grains, which ultimately results in the grains being completely covered by subgrains. Meanwhile, the continuously broken long-period stacking-ordered (LPSO) phase and the precipitated bright rare earth rich (RE-rich) phase provide a large number of nucleation sites, further promoting the refinement process of the grains. Subsequently, the grains were further refined to nanocrystallines through the formation and rotation of subgrains under continuous loading of stress. The massive formation of nano-precipitated phases (β phases) along grain boundaries were accompanied by the complete disappearance of other types of second phases. The sources of β phases formation include the layer-by-layer decomposition of the cellular phases and the dissolution/re-precipitation of the LPSO phases. In addition, the introduction of shear stress promotes the random orientation of the DRXed grains through the extensive activation of pyramidal <a> and pyramidal <c+a> slip. The hardness of the alloys gradually decreased as the cumulative strain decreased at different deformation temperature conditions. When the deformation temperature was 440°C, the alloys reached a maximum hardness of 127.67 HV, which was nearly 43.5% higher than homogenized alloys. The ultra-high hardness of the alloys prepared by severe shear deformation is mainly attributed to grain boundary hardening, diffusion hardening and hetero-deformation induced (HDI) hardening.

Анализ характера течения металла при изготовлении авиационных панелей из различных групп алюминиевых сплавов методами изотермической штамповки

The article discusses the results of studies of the features of the formation of shape defects that occur during the manufacture of aircraft panels, shells and other finned parts from aluminum alloys under conditions of isothermal forging and forging in a state of superplasticity. The formation of defects in the manufacture of panels from various groups of aviation aluminum materials, in particular from alloys based on the Al – Mg system, alloys based on the Al – Mg – Si – Cu system, aluminum alloys of the Al – Zn – Mg – Cu system and alloys of the Al – Mg – Li. The mechanisms of the formation of such shape defects that occur during the production of aircraft panels by isothermal stamping are determined as: a sink on the back side of the panel web in the subcostal space, a rupture of the material of the product in the area of the articulation of the rib and the panel web at the final stages of deformation, the formation of a clamp on the side surface of the rib, the appearance of retracted in the body of the product oxide captivity in the central part of the rib. The dependences of the formation of all the previously mentioned defects on the conditions of the temperature-rate parameters of the deformation process are analyzed. Models of the nature of the metal flow during filling of the die cavity at various temperature-speed parameters of deformation are constructed. It has been established that the nature of the metal flow when filling the die cavity depends on a number of parameters, namely: the thickness of the web of the original slab, the temperature conditions of deformation, the speed conditions of deformation, the ratio of the thickness of the rib and the web of the original slab, the ratio of the height of the rib and the web of the original slab. As a result of the research, the parameters of the processes of deformation of aluminum alloys for the manufacture of defect-free parts of aviation equipment were determined under the conditions of minimizing the consumption rates of basic materials.

Deformation Temperature Conditions Providing Prescribed Property Uniformity for Steel Vessels and a Device for Non-Destructive Control

Deformation Temperature Conditions Providing Prescribed Property Uniformity for Steel Vessels and a Device for Non-Destructive Control

Hot Deformation Behavior of a Beta Metastable TMZF Alloy: Microstructural and Constitutive Phenomenological Analysis

A metastable beta TMZF alloy was tested by isothermal compression under different conditions of deformation temperature (923 to 1173 K), strain rate (0.172, 1.72, and 17.2 s−1), and a constant strain of 0.8. Stress–strain curves, constitutive constants calculations, and microstructural analysis were performed to understand the alloy’s hot working behavior in regards to the softening and hardening mechanisms operating during deformation. The primary softening mechanism was dynamic recovery, promoting dynamic recrystallization delay during deformation at higher temperatures and low strain rates. Mechanical twinning was an essential deformation mechanism of this alloy, being observed on a nanometric scale. Spinodal decomposition evidence was found to occur during hot deformation. Different models of phenomenological constitutive equations were tested to verify the effectiveness of flow stress prediction. The stress exponent n, derived from the strain-compensated Arrhenius-type constitutive model, presented values that point to the occurrence of internal stress at the beginning of the deformation, related to complex interactions of dislocations and dispersed phases.

The mechanism of dynamic strain aging for type A serrations in tensile curves of a medium-Mn steel

The objective of the present study is to clarify the mechanism of dynamic strain aging (DSA) causing serrations in tensile flow curves of Fe-5.15Mn-0.15C-0.37Si-0.0039N (wt%) medium-Mn steel specimens with triple phases of retained austenite (γR), ferrite (α) and tempered martensite (α'T). For the purpose, tensile tests were performed at various conditions of deformation temperature (Td = 273 - 333 K) and initial strain rate (έini = 5 × 10−4 - 1 × 10−2 s−1). The medium-Mn steel specimens revealed type A serrations after the propagation of the Lüders band in their tensile curves. The serrations were not related to both α and α'T; they were not caused by strain-induced martensitic transformation, but by DSA in γR. The DSA was not explained by the short-range diffusion model based on the interaction between partial dislocations and C-Mn complexes due to the absence of intersection between staying time and reorientation time. In a viewpoint of the dislocation arrest model involving long-range diffusion, critical strains of γR for serrations (ecγ) were measured. They showed the normal Portevine-Le Châtelier behavior that the ecγ value decreases with increasing Td and with decreasing έini. The activation energy measured using the ecγ values was similar to the activation energy for the dislocation pipe diffusion of C atoms. This result indicates that the DSA occurring in the present medium-Mn steel is explained by the dislocation arrest model involving the long-range pipe diffusion of C atoms, not by the short-range diffusion model involving the reorientation of C-Mn complexes.

Brittle–ductile fabrics and P – T conditions of deformation in the East Pernambuco shear zone (Borborema Province, NE Brazil)

Fabrics of the East Pernambuco shear zone (EPSZ) were studied via microstructural analysis, mineral chemistry and isochemical phase diagram modelling to constrain the pressure and temperature conditions of deformation during shearing. Granitic mylonites show fractured feldspar porphyroclasts embedded in a fine-grained, recrystallized quartzo-feldspathic matrix. These mylonites grade laterally into banded ultramylonites characterized by stretched feldspar clasts alternated with recrystallized quartz bands. Fractures in these ultramylonites are filled by phyllosilicates. The mineral chemistry of the feldspars points to systematic changes between porphyroclasts, grains within fractures and fine-grained mixtures. Quartz crystallographic fabrics in the mylonites suggest activation of prism slip, while the ultramylonites show the activation of both rhomb and basal slip systems. Thermodynamic modelling suggests that the mylonites were formed at 4.75 ± 0.25 kbar and 526 ± 9°C, while the ultramylonites yield conditions of 5.9 ± 1 kbar and 437 ± 17°C. These observations suggest that the EPSZ records a heterogeneous path of strain accommodation, marked by decreasing temperature from its western sector to its eastern termination. The differences in metamorphic conditions are consistent with a transitional, brittle–ductile strain regime. Such characteristics indicate that the EPSZ is a Neoproterozoic shear belt nucleated and heterogeneously exhumed at the brittle–ductile transition, possibly in an intracontinental setting.Supplementary Material: EPMA analysis of feldspars in Caruaru and Gravatá domains and T-X(O2) pseudosections are available at https://doi.org/10.6084/m9.figshare.c.5125957

The Mechanism of Dynamic Strain Aging for Type a Serrations in Tensile Curves of a Medium-Mn Steel

The objective of the present study is to clarify the mechanism of dynamic strain aging (DSA) causing serrations in tensile flow curves of Fe-5.1Mn-0.15C (wt%) medium-Mn steel specimens with triple phases of retained austenite (γR ), ferrite (α) and tempered martensite (α'T ). For the purpose, many tensile tests were performed at various conditions of deformation temperature ( Td = 273 - 333 K) and initial strain rate ( έini = 5 × 10 -4 - 1 × 10 -2 s -1 ). The medium-Mn steel specimens revealed type A serrations after the propagation of the Luders band in their tensile curves. The serrations were not related to both α and α'T ; they were not caused by strain-induced martensitic transformation, but by DSA in γR . The DSA was not explained by the short-range diffusion model based on the interaction between partial dislocations and C-Mn complexes due to the absence of intersection between staying time and reorientation time. In a viewpoint of the dislocation arrest model involving long-range diffusion, critical strains of γR for serrations (ecγ ) were measured. They showed the normal Portevine-Le Châtelier behavior that the ecγ value decreases with increasing Td and with decreasing έini . The activation energy measured using the ecγ values was similar to the activation energy for the dislocation pipe diffusion of C atoms. This result indicates that the DSA occurring in the present medium-Mn steel is explained by the dislocation arrest model involving the long-range pipe diffusion of C atoms, not by the short-range diffusion model involving the reorientation of C-Mn complexes.

Study on Hot Deformation Behavior and Constitutive Relation of Cr-77.5Nb Alloy

Isothermal compression test at constant strain rate for Cr-77.5Nb alloy were performed on Gleeble simulator with conditions of deformation temperature from 800 to 1200°C and strain rate from 0.001s-1to 0.1s-1. The influence of deformation parameters including temperature, strain rate and strain related with flow stress during hot deformation were investigated and the constitutive relation of Cr-77.5Nb alloy was established by stepwise regression method. The result of error analysis shows that the constitutive relation established has high accuracy and can well characterize the hot deformation behavior of this alloy.

Deformation Resistance of Alloy 2.25Cr1Mo0.25V of Heavy Cylinder for Hydrogenation Reactor

2.25Cr1Mo0.25V alloy steel of making heavy cylinder for hydrogenation reactor was taken as research subject. The compression experiment was carried out on Gleeble-3500 thermal simulator under different conditions of deformation temperature, strain rate and deformation degree. The relationship between deformation resistance and deformation temperature, strain rate, deformation degree was analyzed. Two different types (dynamic recovery and dynamic recristallization) of deformation resistance model were established through multiple nonlinear regression method. The relative error of deformation resistance between the calculated value and the measured value was under 10% and the maximum error of the rolling force between the calculated value and the measured value was 9.7%, which showed that this deformation resistant model was accurate and met industry requirements.

Study of Static Recrystallization Microstructure Evolution of 304 Stainless Steel

The effect of various deformation degree and temperature on static recrystallization of 304 stainless steel during two-passes hot compression deformation with the strain rate of 0.1s-1 was investigated by use of Gleeble-1500D thermo-mechanical simulation. It is indicated that deformation degree is the most obvious factor to static recrystallization. Besides, the grain sizes after deformation were also measured by metallographic method. The results show that the grain sizes decreased dramatically with the conditions of deformation temperature (1050°C), holding time (30s) and total deformation degree (0.35). The result has provides the corresponding scientific basis for the quality forecast of 304 stainless steel during hot thermoplastic deformation.

Recrystallization Behaviour of Nb and Ti+Nb Added Ferritic Stainless Steels

The effect of alloying elements and rough rolling condition on the microstructure evolution of ferritic stainless steel has been investigated in order to understand the recrystallization and precipitation behaviour during hot rolling. In the present study, a series of high temperature compression tests with plane strain deformation mode were conducted for Nb added and Ti+Nb added ferritic stainless steels. Compression tests then were subjected to various conditions of deformation temperature, reduction ratio and holding time. After the tests, EBSD mapping and SEM observation were performed to analyze the recrystallization and precipitation behaviour. Nb added and Ti + Nb added steels show an increasing tendency of recrystallization with an elevation of deformation temperature, holding time and reduction ratio. An increase of holding temperature and holding time enlarges the recrystallized regime due to a decrease of activation energy for recrystallization and a growth of recrystallized grain. A higher reduction ratio also increases the recrystallized regime due to a rise of stored energy for recrystallization. Nb added steel, however, is more resistant to recrystallization because most of Nb (C, N) particles in Nb added steel are finely dispersed in the matrix.

Modelagem metalogenética para prospecção de urânio nas rochas do núcleo da Anticlinal Abaíra-Jussiape, Chapada Diamantina, Bahia

The NNW-SSE-trending Abaira-Jussiape Anticlinal is an antiformal culmination of folding and shearing in the Paramirim Corridor of the Western Chapada Diamantina. In its core Paleoproterozoic, mylonitized Caraguatai Suite, tonalites-granodiorites, alkali-feldspar granites, syenites to quartz-syenites and Jussiape Suite granites crop out. Compressional and distensional stresses mark the structural geology of the area. The compressional structures are related to two distinct deformation phases, named D1a and D1b. The main compressional phase is ductile D1a, which is related to the nucleation of dextral to dextral-reverse shearing zones. Deformation and syn-D1a recrystallization involving plagioclase and the K-feldspar suggest deformation temperature conditions above 550°C. The following phase D2 is of ductilebrittle nature and culminates in reverse shearing zones. The distensional structures correspond to the D3 phase and are represented by frontal shear zones with normal movement. The petrographic study helped identify a pre-D1a hydrothermal alteration process related to albitization and potassification, syn-D1 oxidation process, and hydration and saussuritization related to phases D2 and D3. The integration of lithological, petrographic, structural and geophysical data by means of the logic Fuzzy, plus the existing information regarding structural and lithologic controls of the known uranium mineralization in the Paramirim Corridor, led us to identify two promising areas for radioactive element exploration in the nucleus of Abaira-Jussiape Anticlinal.

Compression Superplasticity of Ultrahigh Carbon Steel in Electric Field

Taking 1.4%C and 1.6%C ultrahigh carbon steels (UHCSs) with ultra-fine structures developed through thermo-mechanical processing as research objects, the influences of superplastic deformation conditions and electric field on compression superplasticity were conducted without electric field and with electric field. The experimental results indicate that 1.4%C and 1.6%C UHCSs have respectively superplasticity or electro-superplasticity under the conditions of deformation temperature of 800°C, the initial strain rate of 0.75-3.75×10-4 s-1 and deformation temperature of 780 °C, the initial strain rate of 0.5-5.0×10-4 s-1 and the suitable external electric field. Its strain rate sensitivity are respectively 0.32 and 0.46.When the electric field intensity of 3 kV/cm in the manner of the specimen connected to positive terminal, the steady flow stress of 1.6%C UHCS decreases more than 10.5% as compared with electric field intensity of 0 kV/cm.

Influence of preliminary elastoplastic yclic deformation on the mechanical characteristics of 1201 alloy at cryogenic temperatures

1. Preliminary elastoplastic deformation for 100 load cycles increases the tensile strength of 1201 alloy. 2. For each test temperature cycle the level of deformation stresses at which the extreme (maximum or minimum) strength in failure occurs was determined. 3. Preliminary mechanical deformation by pulsating tension decreases the plasticity of 1201 alloy, and the rate of decrease in plasticity depends both upon the temperature conditions of deformation and upon the failure temperature.