High Temperature Plane Strain Compression Research Articles

Texture Evolution by Strain-Induced Boundary Migration during Hot Deformation of Fe-3.0 wt.% Si Alloy: Experiment and Modeling

Texture and microstructure evolution during high-temperature plane-strain compression in Fe-3.0 wt.% Si alloy has been investigated by micro-texture analysis and modeling. In this study, hot deformation test is performed on the temperature range of 900 °C~1150 °C with a strain rate scope of 0.01 s−1~5 s−1, and the effect of deformation parameters is investigated by means of electron backscattered diffraction. Nucleation and growth assisted by strain-induced boundary migration result in strong {001}<110> and {001}<210> texture components with low Taylor factors, and the grain size of λ fiber increases significantly by consuming the {111}<110> and {111}<112> texture components with high Taylor factors. The critical Taylor factor above which nucleation by strain-induced boundary migration cannot occur, decreases continuously during hot deformation. With the decreasing critical Taylor factor, the increment rate of low-Taylor-factor orientation depends more sensitively on Taylor factor than the decrement rate of high-Taylor-factor orientation. The boundary separating enhanced and weakened orientations moves towards lower Taylor factor with the deformation proceeding, and medium-Taylor-factor texture components may experience a reversed change from enhancement to weakness. A quantitative model is proposed to describe texture development by incorporating the oriented nucleation probability dependent on a variable critical Taylor factor and the selective growth driven by a variable Taylor factor difference between adjacent grains. The present work can provide an efficient method for optimizing hot deformation texture by means of strain-induced boundary migration.

Characterization and Calculation of the Dynamic Recrystallization Texture in Fe-3.0 Wt.% Si Alloy.

High-temperature plane-strain compression tests were performed on Fe-3.0 wt.% Si alloy from 900 °C to 1150 °C at strain rates of 5 s−1 to 1 s−1, and the texture development from different initial textures was investigated by means of electron backscattered diffraction. Dynamic recrystallization occurs by strain-induced boundary migration, and the evolutions of the microstructure and different texture components vary with the initial texture. The critical orientation boundary separating the weakened and enhanced texture components moves with the initial texture, and a quantitative relationship is established to represent the dependence of the critical Taylor factor on the instantaneous texture. A model is proposed to describe the dynamic recrystallization texture by incorporating the oriented nucleation probability with a variable critical Taylor factor. The present work could improve the accuracy of hot deformation texture prediction based on strain-induced boundary migration.

Role of non-basal slip systems on the microstructure and texture development of ZXK-Mg alloy deformed in Plane Strain Compression at elevated temperature

This work investigates the deformation mechanisms active during high temperature plane strain compression and their impact on the microstructural and texture evolution of an Mg-Zn-Ca-Zr (ZXK) alloy. The microstructures of samples deformed at different strains and different loading directions were examined using electron backscatter diffraction measurements. Likely activated slip systems in grains and twins were determined by in-grain misorientation axis (IGMA), and their activity was compared to the simulation results using the Viscoplastic Self-Consistent (VPSC) model. The importance of the active deformation modes on texture development, specifically the formation of particular texture components, has been linked with a profuse activity of non-basal <a> dislocations and the preferential activation of pyramidal I <c+a> slip over pyramidal II <c+a> slip. Along with prismatic <a> slip, the activation of {101¯2} twins and pyramidal <a> slip seems to be pivotal for the stabilization of the so-called TD-texture component in a specific loading configuration.

Mechanism of Texture and Microstructure Evolution during High Temperature Plane Strain Compression in AZ31B and AZ80 Magnesium Alloys with Various Initial Textures

Mechanism of Texture and Microstructure Evolution during High Temperature Plane Strain Compression in AZ31B and AZ80 Magnesium Alloys with Various Initial Textures

The effect of continuous deformation behaviors on texture formation in magnesium alloy

In previous study, it was investigated texture formation behavior of high temperature compression test in various AZ magnesium alloy. These authors investigated AZ31, AZ61, AZ80 and AZ91 magnesium alloy of compression test at temperature 673K to 723K, a strain rate of 5.0x10−2s−1, and a strain -0.4 to -1. It was found two characteristics of texture formation behaviour – 1) the basal texture was increase with solute concentration increasing, 2) the main texture component developed depending on deformation conditions. However, additional experiment was needed to clarify why the development of these texture occur. Therefore, this study investigated the mechanism of texture development behaviors in the AZ91 magnesium alloy with three different types initial textures during high-temperature plane strain compression deformation. This compression test conditions were temperature of 673K to 723K, and a strain rate of 5.0x10−4s−1, with up to a strain -1.0. After compression test, the specimens were immediately quenched in water. The texture measurement was conducted by the Schulz reflection method using Cu Kα radiation and EBSD. As a result, in all specimens, fiber texture was formed at located at a position 25° away from (0001) texture. In addition, changes in the main component occurred depending on the temperature and the initial texture.

Texture Formation Behaviour during High-Temperature Plane Strain Compression Deformation in AZ91 Magnesium Alloy

In previous study, it was investigated texture formation behaviour of high-temperature plane strain compression test at 723K, under a strain rate of 5.0. It was found that the main texture component and it was sharpness vary depending on deformation conditions. To clarify the characteristic of texture formation behaviour, it is necessary to investigate at various deformation condition. Therefore, in this study, is investigating the influence or texture formation behaviour and strain, strain rate at 673K. Three kinds of specimens with different initial textures were machined out from a rolled plate having a &lt;0001&gt; texture. The plane strain compression tests were conducted at a temperature 673K, and a strain rate of 5.0, with strain between-0.4 to-1.0. After compression tests, the specimens were immediately quenched in oil. The texture evolution was conducted by the Schulz reflection method using Cu Kα radiation and EBSD. Before the deformation, {0001} of specimen A was accumulated in the center of pole figure. The {0001} of specimen B was accumulated at the RD direction. The {0001} of specimen C was accumulated TD direction. As a result, work softening is observed in all the cases at the true stress – true strain curve for three types of specimens. After deformation, the maximum pole density of increases with increasing strain. In this study, it was found that the stable orientation was (0001)&lt;100&gt; and (0001)&lt;110&gt; during deformation.

Dynamic recrystallization behaviour of AlxCoCrFeNi high entropy alloys during high-temperature plane strain compression

AlxCoCrFeNi high entropy alloys (HEAs) with Al molar ratios of 0.3, 0.6 and 0.9 were subjected to hot plane strain compression testing at varying strain rates and strains in the temperature range of 930–1030 °C. A detailed analysis of the flow curves and microstructural evolution of these alloys was conducted under different hot working conditions. Very slow dynamic recrystallization kinetics and a relatively high activation energy of hot deformation (Q=549 kJ/mol) were found for the Al0.3CoCrFeNi FCC HEA. The main restoration mechanism for this alloy was the formation of new grains through strain-induced migration of the grain boundaries. Increasing the Al content to 0.6 and 0.9 molar ratio changed the microstructure to a duplex one comprising of FCC and BCC phases. A complex restoration behaviour was observed for the FCC phase in the duplex structures consisting of discontinuous dynamic recrystallization at the vicinity of the interphases, and a gradual evolution of substructures resembling continuous dynamic recrystallization within the grains in regions far from interphases. The main softening mechanism within the BCC phase in the duplex microstructures was continuous dynamic recrystallization, characterised by a progressive conversion of low-misoriented subgrains into grains bounded by a mixture of low and high angle grain boundaries.

High-Temperature Deformation Behavior of Ti-6Al-2Sn-4Zr-2Mo Alloy with Lamellar Microstructure Under Plane-Strain Compression

High-temperature plane-strain compression of a Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) alloy with a lamellar structure was applied by a thermal simulation machine Gleeble 3800 at a temperature of 1223-1370 K and a strain rate of 0.01-10 s−1. Constitutive relations between the flow stress and strain at different temperatures and strain rates were constructed based on the Arrhenius equation. Processing maps based on the dynamic material model at strains of 0.5, 1.0, and 1.25 were also constructed to analyze the mechanism and instability of high-temperature deformation. Dynamic recrystallization was found to occur at 1223-1313 K and 0.01-0.1 s−1, with a peak efficiency of power dissipation of 70%. Observations of the microstructure demonstrated that α platelets and dynamic globularization were responsible for dynamic softening in the α + β phase field. Flow instability behaviors occurred at 1263-1343 K/1.78-10 s−1, 1233-1283 K/0.1-3.16 s−1, and 1353-1373 K/0.56-1.78 s−1, and adiabatic shear bands and microcracks were observed in these domains. Thus, for the lamellar Ti-6242 alloy, the recommended hot rolling parameters were 1243-1333 K and 0.01-0.1 s−1. Electron backscattered diffraction results revealed that the dynamic restoration mechanism in the β phase field was dynamic recovery when the strain rate was as high as 10 s−1.

Establishment of the High Temperature Constitutive Relationship of the Haynes 230 Ni-Based Superalloy

The high temperature flow behavior of materials is an important basis to study their formability and to determine reasonable forming process parameters. In this work, the high temperature plane strain compression (HTPSC) tests were employed to reveal the high temperature flow behavior of Haynes 230 Ni-based superalloy under the wide range of temperatures (950°C-1200°C) and strain rates (0.01/s-10/s). The stress-strain data from the tests were applied to model the strain-compensated Arrhenius physically-based constitutive equation and considering the dynamic recovery (DRV) and dynamic recrystallization (DRX) phenomenological constitutive equation. The comparison indicated that the predictions of the two modeled constitutive equations are in good agreement with the experimental data. The prediction of the flow behavior of Haynes 230 Ni-based superalloy of strain-compensated Arrhenius constitutive equation is more accurately (average absolute relative error (AARE) is 2.84%) than that of considering DRV and DRX constitutive equation (AARE is 7.57%).

Research on precise control of microstructure and mechanical properties of Ni-based superalloy cylindrical parts during hot backward flow spinning

Ni-based superalloy cylindrical parts widely used in the fields of aviation and aerospace have high requirements for the microstructure and mechanical properties. Hot flow spinning is an effective forming technology for manufacturing cylindrical parts with thin walls. The high-temperature plane strain compression test was put forward as the physical simulation test of hot backward flow spinning (HBFS) of cylindrical parts, and a new method for controlling the microstructure and mechanical properties of spun parts precisely based on hot processing map was proposed as the basis of selecting the reasonable processing parameters of HBSF. The results show that the relationships between the large true strains and stresses of Haynes 230 alloy during HBFS can be obtained effectively by the high-temperature plane strain compression test; the reasonable processing parameters which are beneficial for dynamic recrystallization and hot plastic deformation can be selected directly on the basis of the hot processing map. The influence of the processing parameters of HBSF on the microstructure of Haynes 230 cylindrical spun workpiece was also investigated, the results show that the influence of thinning ratio and forming temperature on the microstructure of the spun workpiece is remarkable, while the average grain size of spun workpiece decreases slightly with the increasing of feed rate. The yield strength and tensile strength of the Haynes 230 cylindrical spun part at the temperature of 800°C are both increased obviously compared with the original cylindrical blank, and the elongation is also slightly increased, which is particularly helpful in the high-temperature service of the Ni-based superalloys.

Investigation of hydrogen influencing γ-phase true and pseudo twinning in a TiAl based alloy during high-temperature plane strain compression

In this paper, the effect of hydrogen on true and pseudo twinning of γ phase in a TiAl based alloy was investigated by means of plane strain compression tests at elevated temperature. The results showed that hydrogen could increase true- and pseudo-twin boundaries of γ phase. Hydrogen-decreased stacking fault energy, hydrogen-promoted Shockley dislocation movement, hydrogen-decreased stacking fault energy and hydrogen-enhanced element diffusion promoted γ-phase mechanical twinning and grain boundary migration. Furthermore, more γ-phase mechanical twinning and grain boundary migration led to more true-twin boundaries. Additionally, hydrogen could promote order twinning. The interaction between true- and order-twin boundaries cloud result in pseudo-twin boundaries. Therefore, hydrogen-promoted true and order twinning could indirectly increase pseudo twinning.

Particle stimulated nucleation during dynamic and metadynamic recrystallisation of Ni-30%Fe-Nb-C alloy

For the first time, a combination of scanning transmission electron microscopy and electron back-scattering diffraction is used to elucidate the early stages of particle stimulated recrystallisation at Nb carbides in Ni-30wt.%Fe alloy subjected to high temperature plane strain compression. While particles with sizes even below 1μm were found to induce dynamic or metadynamic recrystallisation, only a small fraction of coarse particles served as nucleation sites.

高温平面ひずみ圧縮変形下でAZ31マグネシウム合金に生ずる特異な結晶粒組織と集合組織の繰り返し変化

高温平面ひずみ圧縮変形下でAZ31マグネシウム合金に生ずる特異な結晶粒組織と集合組織の繰り返し変化

Texture Formation Behaviors in AZ80 Magnesium Alloy during High-Temperature Plane Strain Compression

The behavior of texture formation during high-temperature deformation in AZ80 magnesium alloy is investigated. Three kinds of specimens were machined out from rolled plates. The plane strain compression tests were conducted at various deformation conditions – temperature, strain and strain rate. After compression deformation, texture measurement was carried out on the mid-plane section parallel to the compression direction by the Schulz reflection method and EBSD measurement. The maximum values of the flow stress are observed in all the cases at the true stress – true strain curve for three type of specimens. It is found that the main component of texture and the accumulation of pole density vary depending on deformation condition and initial texture. Six kinds of crystal orientation components have been observed after deformation in total. (0001)&lt;10-10&gt; is formed regardless of the initial texture.

Formation behavior of basal texture under the high temperature plane strain compression deformation in AZ80 magnesium alloy

The formation behavior of basal texture during high temperature deformation of AZ80 magnesium alloys in single phase was investigated by plane strain compression deformation. Three kinds of specimens with different initial textures were machined out from an extruded bar having a <101̄0> texture. Plane strain compression tests were conducted at temperatures of 623K and 723K and a strain rate of 5.0×10-2s-1, with a strain range of between - 0.4 and -1.0. After deformation, the specimens were immediately quenched in oil. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. Electron backscatter diffraction (EBSD) measurements were also conducted in order to examine the spatial distribution of orientations. Three kinds of specimens named A, B and C were prepared from the same extruded bar. In the specimens A, B and C, {0001} was distributed preferentially parallel to ND, TD, and RD, respectively. After deformation, texture evaluation was conducted on the mid-plane section. At the plane strain compression deformation, peaks appeared in the true stress-true strain curves irrespective of the kinds of specimen used. It was found that the main components and the pole densities of the textures vary depending on deformation condition and initial texture. Six kinds of texture components were observed after deformation. The (0001)<101̄0> has formed regardless of the initial texture. There are two types of texture components; one exists before the deformation, and the other does not. Either types are considered to have stable orientations for plane strain compression. Also, the basal texture is composed of two crystal orientation components - (0001)<101̄0> and (0001)<112̄0>. When (0001) existed before deformation, an extremely sharp (0001) (compression plane) texture is formed.

Texture development in Fe–3.0 mass% Si during high-temperature deformation: Examination of the preferential dynamic grain growth mechanism

A new mechanism of texture evolution, named “preferential dynamic grain growth mechanism”, is examined experimentally by high-temperature plane-strain compression deformation of Fe–3.0mass% Si alloy. The proposed mechanism is based on preferential growth of the orientations having low Taylor factors and stability against deformation. According to the mechanism, the growing orientation is expected to be {001}〈110〉 in the case of plane-strain compression deformation. In fact, the textures formed by deformations up to the desired strain of −1.0 have high orientation densities around {001}〈110〉 in accordance with the proposed mechanism. With decreasing strain rate, the volume fraction of {001}〈110〉 increases with the increase in the average intercept length of crystal grains along the transverse direction at both 1093K and 1173K, which implies the occurrence of dynamic grain growth during the deformation. The volume fraction of {001}〈110〉 is higher at 1173K than at 1093K for the same strain rate. Electron backscatter diffraction measurements show that the density of small-angle grain boundaries decreases with increasing temperature and decreasing strain rate. The lower density of small-angle grain boundaries implies that distribution of dislocations in grains approaching homogeneity results in the enhancement of preferential dynamic grain growth at higher temperatures and lower strain rates. This suggests that high-temperature deformation might be applied as a new method for controlling texture.

High temperature deformation of silicon steel

The microstructure and texture development during high temperature plane strain compression of 2% in weight silicon steel was studied. The tests were carried out at a constant strain rate of 5 s−1 with reductions of 25, 35 and 75% at temperatures varying from 800 to 1100 °C. The changes in microstructure and texture were studied by means of scanning electron microscopy and electron backscattered diffraction. The microstructure close to the surface of the samples was equiaxed, which is attributed to the shear caused by friction, whereas that at the centre of the specimens was made of a mixture of elongated and fine equiaxed grains, the last ones attributed to the action of dynamic recovery followed by recrystallization. It was found that the volume fraction of these equiaxed grains augmented as reduction and temperature increased; a 0.7 volume fraction was accomplished with a 75% reduction at 1100 °C. The texture of the equiaxed and elongated grains was found to vary with the increase of deformation and temperature, as the γ-fibre tends to disappear and the α-fibre to increase towards the higher temperature range.

Texture Evolution in AZ80 Magnesium Alloy by the Plane Strain Compression Deformation at High Temperature

The formation behavior of textures during high temperature plane strain compression deformation is experimentally studied on AZ80 magnesium alloy. Three kinds of specimens with different initial textures are prepared from the extruded bars having a h10� 10i fiber texture. Plane strain compression is conducted at 723K, 5.0 © 10 ¹2 s ¹1 and strains ranging from ¹0.4 to ¹1.0. New grains appeared after the deformation up to ¹0.4 in true strain. Initial texture gradually changes with increasing strain. After the deformation up to ¹1.0 in true strain, (0001)h10�i, f11� 20gh10� 10i, (0001)h11�i and f10�gh0001i appeared depending on the initial texture. (0001)h10� 10i and f11�gh10�i are formed irrespective of the initial texture. Simple crystallographic examination showed that all the texture components are orientations stable for the plane strain compression. [doi:10.2320/matertrans.L-M2012828]

Formation Process of Texture in AZ80 Alloy during High Temperature Plane Strain Compression Deformation

Formation process of textures in AZ80 is investigated on polycrystal specimens with different initial textures by plane strain compression deformation at 673 K and 723 K with strain rates between 5.0×10-4s-1 and 5.0×10-2s-1. Three kinds of specimens were taken out from the extruded bars with (direction of the extrusion) fiber texture by changing the geometrical relationship with the extrusion direction. In the case of the specimen having parallel to the compression direction before deformation, the initial fiber texture gradually transformed into several orientations with increasing strain at 723K with a strain rate of 5.0×10-2s-1. oriented grains, which was not seen in the pole figures before deformation appeared after the deformation up to -1.0 in true strain. The other two kinds of specimens have compression directions perpendicular to direction. The textures after deformation of these two kinds of specimens also consisted of several components. Some of them are common among the three kinds of specimens and the others are retained components of the initial texture.

Texture Evolution during High Temperature Plane Strain Compression of High Silicon Steels

High silicon steel is used for electrical applications because its electrical resistivity is increased and the magnetostriction is reduced. A silicon content up to 6.5 wt.-% gives excellent magnetic properties. The improvement of the magnetic properties stays in contrast with the lack of ductility of these alloys, making their thermo-mechanical processing difficult. The optimum final microstructure and texture depends on the final application of the material: extremely big grains with a Goss orientation ({110} &lt;001&gt;) are desired in transformers and grains with an average size of 100 -m and cube component ({100} &lt;001&gt;) are used in electrical motors. A series of plane strain compression (PSC) tests were performed on 3 electrical steels, with a silicon content from 1.8 to 4.1 wt.-%, in a temperature range of 800 to 1100°C, strain rates between of 0.5 and 5 s-1. Reductions and time between deformation and quenching were also varied in order to study the recrystallisation progress. Apparent activation energies for hot working, calculated using the hyperbolic sine equation, was in good agreement with literature and higher than the activation energy for self diffusion in iron. These values increase with the silicon content. The high temperature texture evolution was investigated by means of electron back scattering Diffraction (EBSD) technique, which allows the quantification of important texture components in function of the thermo-mechanical parameters applied during hot rolling and the plane strain compression tests. The hot rolled microstructures have shown an average grain size of 140 -m and a texture with a maximum on the cube fibre ({001} &lt;-1-10&gt;). The conventional α (&lt;110&gt; // RD) / γ (&lt;111&gt; // ND) fibre texture was developed after plane strain compression and their intensities depend on the deformation temperature and reduction. A similar tendency was observed for the fraction of static recrystallised grains.