High Temperature Compressive Deformation Research Articles

Effect of anisotropic microstructure on high-temperature compression deformation of CoCrFeNi based complex concentrated alloy

Effect of anisotropic microstructure on high-temperature compression deformation of CoCrFeNi based complex concentrated alloy

Texture formation behaviors of Mg-9Al-1Zn alloy during high-temperature compression deformation

The formation behavior of basal texture during high temperature deformation of AZ91 magnesium alloys in single phase was investigated by plane strain compression deformation. Three kinds of specimens with different initial textures were machined out from a rolled plate having a texture. The plane strain compression tests were conducted at a temperature of 723 K and a strain of 5.0 × 10-2s-1, with a strain range between -0.4 and -1.0. After deformation, the specimens were immediately quenched in oil. Before deformation, specimen A, {0001} was distributed at the center of pole figure; specimen B shows {0001} was distributed at TD direction; and specimen C, {0001} was distributed at RD direction. Texture evaluation was conducted by Schulz reflection method using nickel-filtered Cu Ka radiation and EBSD. It was found that the main component of texture and the accumulation of pole density vary depending on the deformation condition and the initial texture in all types of specimens. The crystal orientation components in this study were formed by continuous deformation and discontinuous deformation, also when (0001) existed before deformation, an extremely sharp (0001) (compression plane) texture was formed.

Effect of Micro-Alloying Elements on Recrystallization Behavior of Carbon Steels at Different Strain Rates

The present study deals with the effects of micro-alloying elements such as Ni, V, and Ti on the recrystallization behavior of carbon steels at different strain rates. Eight steel specimens were fabricated by varying the chemical composition and reheating temperature; then, a high-temperature compressive deformation test was conducted in order to investigate the relationship of the microstructure and the recrystallization behavior. The specimens containing micro-alloying elements had smaller prior austenite grain sizes than those of the other specimens, presumably due to the pinning effect of the formation of carbonitrides and AlN precipitates at the austenite grain boundaries. The high-temperature compressive deformation test results indicate that dynamic recrystallization behavior was suppressed in the specimens with micro-alloying elements, particularly at increased strain rate, because of the pinning effect of precipitates, grain boundary dragging and lattice misfit effects of solute atoms, although the strength increased with increasing strain rate.

Research on the High-Temperature Hot Compressive Deformation Behavior of Ni-Based Superalloy GH3128

Intermediate heat exchanger (IHX), which transfers the heat generated in the reactor core to the secondary loop, is one of the key structural components of the very high-temperature gas-cooled reactor (VHTR). The Ni-based superalloy GH3128 has good high-temperature strength and so is a promising main structural material for the IHX. In this paper, the flow stress behaviors and the deformation microstructure of superalloy GH3128 were investigated by high-temperature compression tests conducted at various temperatures (950–1150 °C) and strain rates (0.001–10 s−1), and the processing maps were analyzed in order to establish the hot deformation constitutive model and obtain the optimum hot forming condition. The results show that (1) both flow stresses and peak flow stresses increase along with the increase of strain rate or decrease of temperature, (2) GH3128 has excellent hot workability, (3) the dynamic recovery (DRV) plays the dominant role during the dynamic softening process due to the high stack fault energy, and (4) the optimum hot forming condition of GH3128 should be defined in the temperature of 1150 °C and strain rate range of 0.01–0.056 s−1. This work contributes to the application of GH3128 alloy on IHX structure.

Precipitation behavior during high-temperature isothermal compressive deformation of Inconel 718 alloy

The precipitation behaviors of γ″ and δ phases during high-temperature isothermal compressive deformation of Inconel 718 alloy are investigated under the strain rate of 2.2·10−4s−1. It is found that the precipitation behaviors are tailored by deformation temperatures, and lead to the disparately abnormal deformation characteristics. Under the deformation temperature of 800°C, the microstructure is composed of incoherent needle-shaped γ″ precipitates at grain boundaries and ultrafine spherical γ″ particles within grains, resulting in the exceptional decrease of flow stress with absence of DRX. When deformed at 900°C, it becomes needle-shaped δ precipitates at grain boundaries and intragranular disc-shaped γ″ precipitates, and the DRX softening degree is lowered consequently.

Strain rate-dependent high temperature compressive deformation characteristics of ultrafine-grained pure aluminum produced by ECAP

To explore the effect of strain rate ▪ on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain rates ▪ were systematically studied through compression tests and microscopic observations. The increase in ▪ eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473–573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10−3 s−1; however, at 1×10−2 s−1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in ▪ inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.

Effect of high temperature compression deformation strain rate on the microstructure and corrosion behavior of 2205 duplex stainless steel

Purpose – The aim of this paper was to investigate the effect of strain rate on microstructure and corrosion behavior of 2205 duplex stainless steel, after high-temperature compression tests. Design/methodology/approach – The specimens were prepared using a Gleeble3800 thermo-simulation machine over a range of temperatures from 850 to 1,250°C and strain rates from 0.005 to 5 s−1, and the corresponding flow curves and deformation microstructure obtained were further analyzed. To evaluate the effect of strain rate on corrosion behavior, potentiodynamic polarization tests and double-loop electrochemical potentiodynamic reactivation (DL-EPR) were used to characterize the electrochemical performance. Findings – Compared with strain rate of 0.5 s−1, the worst corrosion resistance behavior from the potentiodynamic polarization test results after deformation at 0.005 s−1 was attributed to more austenite (γ) and ferrite (δ) grain boundaries or δ/γ phase interface formation due to the better effect of γ dynamic recrystallization (DRX) or δ dynamic recovery (DRV). Increasing strain rate to 5 s−1 lowered the corrosion resistance, due to the increase in dislocation density. At the low strain rate of 0.005 s−1, the susceptibility to intergranular corrosion (IGC) was comparatively high after deformation at 1050 and 1150°C with more γ/γ grains and δ/γ phase boundary formation, which was lowered with the strain rate increase to 0.5 s−1, due to suppressing effect of γ DRX. Originality/value – The paper provides the scientific basis for the practical application of hot working of 2205 duplex stainless steel.

High Temperature High Strain-Rate Tensile and Compressive Deformation Behaviors of Cu-Zn-Sn-Al Alloy

The present work gives a systematic study on the high temperature and high strain-rate deformation behaviors of a two-phase α/β Cu-Zn-Sn-Al alloy, by combining the split Hopkinson bar experiments and microstructural investigations. The results show that under high strain-rate, both the dislocation slip and deformation twins within the α phase contribute to the plastic strengthening of Cu-Zn-An-Al alloy, resulting in the strain-rate-hardening effect. As the deformation temperature increases, the shapes of the stress-strain curves are mainly influenced by the temperature-softening effect and the dynamic recrystallization of the α phase. Finally, material constants regarding the strain-rate-hardening and temperature-softening effects are determined, based on the Johnson-Cook constitutive model. The results show that compared with other metallic materials, the present Cu-Zn-Sn-Al alloy has a relatively stronger strain-rate-hardening effect and weaker temperature-softening effect.

High Temperature Deformation Behaviors and Constructive Relation of the Porous Cu-Ni-Al Sintered Alloys

The Cu-Ni-Al powders are prepared by atomization method, are hot pressing sintered in the vacuum furnace to prepare the porous Cu-Ni-Al alloy. The microstructure, high-temperature compressive deformation behavior and its effect factors are investigated,respectively. The deformation mechanism of the porous Cu alloy is also analyzed and discussed. The results show that the compression strength, elastic modulus and yield strength decrease with increasing temperature and decreasing strain rate. The compression deformation process is classified in terms of three stages of linear elastic deformation, yield platform area with pore wall buckling, collapse, and plastic deformation with pore densification. In the high temperature compression deformation process, stress concentration and deformation are preferred to occur at the areas with pore concentration and thinner pore walls. The compressive mechanical model of the porous Cu alloy is established using the method of linear regression. It is obvious that the calculation curves is in accordance with the experimental curves in the first and second stages of the deformation process, however, at the third stage,the former is above the experimental curves, which is possibly attributed to the inhomogeneous pore distribution of the porous Cu alloy.

Dynamic recrystallization behavior of an as-cast TiAl alloy during hot compression

High temperature compressive deformation behaviors of as-cast Ti–43Al–4Nb–1.4W–0.6B alloy were investigated at temperatures ranging from 1050°C to 1200°C, and strain rates from 0.001s−1 to 1s−1. Electron back scattered diffraction technique, scanning electron microscopy and transmission electron microscopy were employed to investigate the microstructural evolutions and nucleation mechanisms of the dynamic recrystallization. The results indicated that the true stress–true strain curves show a dynamic flow softening behavior. The dependence of the peak stress on the deformation temperature and the strain rate can well be expressed by a hyperbolic-sine type equation. The activation energy decreases with increasing the strain. The size of the dynamically recrystallized β grains decreases with increasing the value of the Zener–Hollomon parameter (Z). When the flow stress reaches a steady state, the size of β grains almost remains constant with increasing the deformation strain. The continuous dynamic recrystallization plays a dominant role in the deformation. In order to characterize the evolution of dynamic recrystallization volume fraction, the dynamic recrystallization kinetics was studied by Avrami-type equation. Besides, the role of β phase and the softening mechanism during the hot deformation was also discussed in details.

High temperature deformation behavior of near γ-phase high Nb-containing TiAl alloy

High temperature compressive deformation behaviors of a high Nb-containing PM-TiAl alloy (Ti–45Al–7Nb-0.3 W, at.%) were investigated at temperatures ranging from 1050 °C to 1200 °C, and strain rates from 0.001 s−1 to 1 s−1. The microstructure mainly consists of γ phase. The data obtained from the flow curves were employed to develop the constitutive equation, and the apparent activation energy (Q) was determined to be 414 kJ mol−1. The size of the dynamically recrystallized grains (DRX) decreased with the increasing value of Zener–Hollomon (Z) parameter. A processing map was constructed on the basis of the flow stress, and the condition of intermediate Z (1150 °C, 0.1 s−1) was determined to be the optimum hot forging parameter for industrial productions. DRX was observed under all the deformation conditions. At high Z and intermediate Z condition, dislocation climbing and twinning accompanied by DRX can act as the main deformation mechanisms. At low Z condition, DRX becomes the dominant softening mechanism, accompanied by the bending of lamellar colonies as well as the broken of γ grains and α2 grains.

High temperature compressive deformation behavior of ZA27–SiC foam

Compressive deformation behavior of closed cell zinc aluminum alloy (ZA27)–SiC composite foams with varying relative densities has been studied at varying strain rates (0.001–1s−1) and temperatures (100–250°C). The compressive deformations of these foams are characterized in terms of plateau stress, densification strain and energy absorption capacity as a function of cell size, relative density, strain rate and temperature. Plateau stress and energy absorption increase with increase in relative density and strain rate; and decrease with increase in temperature. The densification strain on the other hand is noted to be almost invariant to the cell size, strain rate and temperature. The plateau stress, however, decreases marginally with cell size. On the other hand, the energy absorption decreases comparatively to a larger extent with increase in the cell size. This has been discussed in line with the deformation mechanism of the ZA27–SiC foam.

High Temperature Compression Deformation Behavior and Rheological Stress Model of HRB400

A series single-pass compression tests of HRB400 slab under the circumstances of different deformation temperature and deformation rate are carried out with Gleeble-1500D thermal simulation testing machine. The experimental results shows as follows. The true stress-true strain curves of the compression process are got from the tests. The state activation energy is 353.542kJ/mol and a mathematical model of high-temperature rheological stress is established. The calculated results by the rheological model are consistent with the experiments.

Effect of Nb particles on the flow behavior of TiAl alloy

High temperature compressive deformation behaviors of PM-TiAl alloy containing Nb particles (Ti–45Al–5Nb–0.4W/2Nb (at. %)) were investigated at temperatures ranging from 1050 °C to 1200 °C, and strain rates from 0.001 s−1 to 1 s−1. The flow curves were employed to develop constitutive equations, and the apparent activation energy of deformation Q was determined as 447.35 kJ/mol. A revised processing map was constructed on the basis of the flow stress, which can accurately describe the deformation behaviors and predict the optimum hot forging condition. The addition of 2% Nb particles reduces the peak stress and increases the activation energy of TiAl-based intermetallic, however, it increases the instable domain in the processing map.

Constitutive equation and processing map for hot compressed as-cast Ti-43Al-4Nb-1.4W-0.6B alloy

High temperature compressive deformation behaviors of as-cast Ti-43Al-4Nb-1.4W-0.6B alloy was investigated at temperatures ranging from 1323 K to 1473 K, and strain rates from 0.001 s−1 to 1 s−1. The results indicated that the true stress—true strain curves show a dynamic flow softening behavior. The flow curves after the friction and the temperature compensations were employed to develop constitutive equations. The effects of temperature and the strain rate on the deformation behavior were represented by Zener-Holloman exponential equation. The influence of strain was incorporated in the constitutive analysis by considering the effect of the strain on material constants by a five-order polynomial. A revised model was proposed to describe the relationships among the flow stress, strain rate and temperature and the predicted flow stress curves were in good agreement with experimental results. Appropriate deformation processing parameters were suggested based on the processing map which was constructed from friction and temperature corrected flow curves, determined as 1343 K, 0.02 s−1 and were successfully applied in the canned forging of billets to simulate industrial work condition.

Constitutive relationship for high temperature deformation of Al-3Cu-0.5Sc alloy

The high temperature compressive deformation behavior of Al-3Cu-0.5Sc alloy was investigated at temperatures from 350 to 500 °C, and strain rates from 0.01 to 10 s−1 with the Gleeble-1500 thermo-mechanical simulator machine. The flow curves after corrections of the friction and temperature compensations were employed to develop constitutive equations. The effects of temperature and strain rate on deformation behaviors were represented by Zener-Hollomon parameter in an exponent type equation. The influence of true strain was incorporated in the constitutive equation by considering the effect of true strain on material constants. A four-order polynomial is found to be suitable to represent the influence of strain on the constitute equations.

The microstructure and flow behavior of 2205 duplex stainless steels during high temperature compression deformation

The deformation behavior of a 2205 duplex stainless steel has been investigated over the range of temperatures from 850 to 1250°C and strain rates from 0.005 to 5s−1 by compression testing. The results show that the characteristics of flow stress curves and deformed microstructures mainly rely on the variations of deformation temperature and strain rate. At a low strain rate of 0.005s−1, the flow curve characteristics of dynamic recrystallization (DRX) were exhibited with deformation temperatures at 950 and 1050°C, whereas the region of stable flow stress became narrower as the strain rate increased to 0.5s−1 at 850 and 950°C, leading to more work hardening deformed microstructures formation. The leading softening effect in flow curves is characterized by dynamic recovery (DRV) with higher deformation temperature at 1150 and 1250°C, and the ferrite grains of DRV became coarser simultaneously. As the strain rates are 0.005 and 0.5s−1, the corresponding austenite content shows the highest at 950 and 1050°C respectively, indicating the best effect of austenite DRX, which was weakened by increasing strain rate to 5s−1. Meanwhile, the values of apparent activation energy and hot deformation equation have been obtained by hot deformation equation analysis.

Perfect High‐Temperature Plasticity Realized in Multiwalled Carbon Nanotube‐Concentrated α‐Al2O3 Hybrid

We investigate the high‐temperature compressive deformation behavior of a novel, fully dense and structurally uniform, 20 vol% multiwalled carbon nanotube (MWCNT)–α‐Al2O3 matrix hybrid, which has a strong room‐temperature interfacial shear resistance (ISR) and a unique MWCNT‐concentrated grain‐boundary (GB) structure. We realized a perfect plastic deformation at 1400°C and a rather high initial strain rate of 10−4 s−1 by a low ~30 MPa flow stress, which is contrary to the strain hardening response of fine‐grain monolithic Al2O3. This unique performance in CNT–ceramic system in compression is explained as follows: the concentrated network of individual MWCNTs perfectly withstands the high‐temperature and shear/compressive forces, and strongly preserves the nanostructure of Al2O3 matrix by preventing the dynamic grain growth, even during a large ~44% deformation. Furthermore, the presence of large amount of radially soft/elastic, highly energy‐absorbing MWCNTs in the GB and specially multiple junction areas, and a potentially weak 1400°C‐ISR, could greatly facilitate the GB sliding process (despite the hybrid's strong room‐temperature ISR), as evidenced by the formation of some submicrometer‐scale MWCNT aggregates in GB area, the equiaxed grains and dislocation‐free nanostructure of the deformed hybrid. The results presented here could be attractive for the ceramic forming industry and could be regarded as a reference for oxide systems in which, the GB areas are occupied with soft/elastic, highly energy‐absorbing nanostructures.

Fe-3mass%Si合金の高温単軸圧縮変形中に生じる優先動的結晶粒成長による集合組織形成に及ぼすP添加の影響

Fe-3mass%Si合金の高温単軸圧縮変形中に生じる優先動的結晶粒成長による集合組織形成に及ぼすP添加の影響

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.