High Temperature Compressive Deformation Research Articles

Effect of hydrogen content on the high-temperature compressive deformation behavior and microstructure evolution of TC17 alloy

Thermo-hydrogen process (THP) has been an important research direction of the titanium alloy heat treatment process. However, the effect of THP on the thermal deformation behavior and microstructure evolution of TC17 alloy during hot compression has not been investigated. In this study, a series of isothermal compression experiments were carried out on hydrogenated TC17 alloy specimens in the temperature range covering the α+β phase region and β phase region of TC17 alloys with different hydrogen contents, to investigate the effect of hydrogen on the high-temperature flow behavior and microstructure evolution. The results show that the primary α phase of the hydrogenated TC17 alloy is significantly reduced. Observing the XRD pattern, the substitutional solution effect of hydrogen causes the β phase lattice to expand, resulting in a shift of the β phase toward a small angle as the hydrogen content increases. The flow stress shows a tendency to decrease and then increase with increasing hydrogen content. This is attributed to the softening effect of hydrogen on the α phase and the hardening effect on the β phase. This also leads to the deformation activation energy showing the same trend. When the hydrogen content increases to 0.4 wt%, the activation energy decreases to the lowest point by about 24 %. Finally, the appropriate hydrogen concentration can effectively reduce the destabilization region in the hot working map and expand the processing window of TC17 alloy.

High-temperature compression deformation strengthening mechanism of Mg–Gd–Y–Zn–Zr alloy formed by cold metal transfer (CMT) arc additive forming

The Mg–Gd–Y–Zn–Zr alloy structural parts were formed by CMT arc additive forming. The high-temperature compression deformation strengthening mechanism of the alloy at 623–723 K, 0.01–1s−1, and 50 % deformation was studied. Upon a decrease in the temperature or an increase in the strain rate, the effect of fine-grain strengthening was obvious, which led to the improvement of the mechanical properties of the alloy after deformation. The grain refinement was mainly attributed to the DDRX and CDRX processes during hot deformation. Because the compression specimen was loaded along the building direction, the twins after deformation were compression twins {10–11}, and the content increased with an increase in the strain rate or a decrease in the temperature. As the strain rate increased, the texture distribution on the {10-10} plane became more concentrated and the texture intensity decreased from 6.79 to 2.24. This was attributed to the fact that the alloy was mainly dominated by a non-basal slip during high-temperature deformation, which increased the sensitivity of the strain rate to the texture.

High-temperature compression deformation behavior of the high Nb-containing TiAl alloys doped with Sn

In this work, the high-temperature compression behavior of high Nb-containing TiAl–Sn alloys was investigated at deformed temperatures of 700 °C–1000 °C and strain rates of 0.002 s−1–0.2 s−1. The true stress-strain curves, microstructures, and constitutive equations of TiAl-xSn (x = 0, 0.5, 1, 1.5) alloys under different deformation conditions were systematically compared. Sn addition can increase the flow stress of TiAl alloys at the same deformation temperature, which is caused by the solid solution strengthening effect. At 800 °C/0.002 s−1, the peak flow stress of TiAl–1Sn alloy increases by 180 MPa compared with TiAl–0Sn alloy of 600 MPa. Below the peak stress, the flow stress increases with the increase of strain. Above the peak stress, the flow stress first decreases and then gradually trends to a steady state as the increase of deformation. Furthermore, the Sn addition decreases the brittle-ductile transition temperature of TiAl alloys. The TiAl-xSn (x = 0.5, 1, 1.5) alloys displays obvious flow softening behavior at 700 °C while TiAl–0Sn alloy fractures before reaching the target deformation. The relationship between of the flow stress, strain rate, and deformation temperature for TiAl–0Sn and TiAl–1Sn alloys is suitable for the hyperbolic sinusoidal equation. The dominant softening mechanism of hot deformation for TiAl-xSn (x = 0, 1) alloys is dynamic recrystallization (DRX). The activation energies Q of hot deformation for TiAl–0Sn and TiAl–1Sn alloys are 311 kJ mol−1 and 429 kJ mol−1 at condition of 700–1000 °C/0.002–0.2 s−1, indicating that the TiAl–1Sn alloy exhibits a better stability under the same application condition.

Revealing the ultra-high high-temperature compressive mechanical properties and deformation mechanism of a heterostructured AlNp/Al nanocomposite

Heterostructured materials have attracted increasing attention owing to their superior mechanical properties. In this work, the high-temperature mechanical property and deformation mechanism of a heterostructured AlNp/Al composite were revealed by isothermal compression tests. The results showed that the superior compressive strength of the AlNp/Al composite could be maintained at both room temperature and high temperature of 300–500 °C during the whole deformation process. The strong pinning effect of the dispersive AlN nanoparticle (AlNp) on the matrix grains could prevent grain boundary softening and grain growth, as well as the special layered heterogeneous structure and network structure could avoid high temperature softening. The hot deformation mechanism of the AlNp/Al composite could be affected by the strain rate and deformation temperature. It was confirmed that continuous dynamic recrystallization (CDRX) dominated the whole deformation process when deformed at low strain rates (0.0001–0.01 s−1) and high temperatures (400–500 °C); while dynamic recovery (DRV) was the main mechanism at high strain rate (0.1–1 s−1) and low temperature (300–350 °C) Furthermore, the strain rate sensitivity exponent (m) was used to assess the relationship between peak stress and deformation temperature and strain rate, which could predict the instability region of the composite. It shows that the simultaneous action of high temperatures and high strain rates should be avoided during hot deformation. This work shed light on the microstructure design of the high-strength heat-resistant aluminum matrix composite.

Recrystallisation Characteristics of a Cu Bearing HSLA Steel Assessed Through High Temperature Compressive Deformation

Dynamic (DRX) operative duringdeformation and static recrystallization (SRX) operative after deformation are considered responsible for the changes in microstructure and texture of deformed materials. Especially in the case of advanced steels that are required in the form of plates of various thicknesses, hot rolling is the main manufacturing process during which the steel undergoes DRX under the rolls and SRX between rolling passes/strands. Knowledge on DRX and SRX characteristics of such steels is crucial for optimisation of hot rolling parameters,achieving the desired microstructure and consequently the targeted mechanical properties.In this study, certain key aspects of both dynamic (DRX) and static recrystallisation (SRX) behaviour of aCu-bearing HSLA steel, which was developed at DMRL, have been explored through high temperature deformation studies using Gleeble thermo-mechanical simulator. Through uniaxial compression testing in the austenitic regime, domains of continuous and discontinuous DRX prevalent in the steel were identified and critical parameters for initiation of dynamic recrystallisation viz., critical strain (ec), critical stress (sc), peak stress (sp) and peak strain (ep) were determined as a function of temperature and strain rate. SRX characteristics were assessed through uniaxial double hit compression tests with fixed strain rate and strain per hit but at different temperatures and with different imposed intermediate static recrystallisation (ISRT) times. From the fractional softening data, parameters such as time for 50% recrystallisation, t0.5, temperature for 50% recrystallisation, T0.5, and activation energy, QSRX have been estimated.Although the steel exhibited good plastic deformation characteristics, the results suggest that the role of copper in retarding recrystallisation is significant.

High-temperature and room-temperature compression deformation behavior comparing of GH4169 Alloy

The hot deformation characteristics of a Ni-Fe based superalloy (GH4169) were studied in the temperature range 900-1020 °C and strain rate range 0.001-0.1 s−1 using hot compression tests. The cold deformation characteristics of the alloy were studied at room-temperature and strain rates of 0.1-1.0 s−1 using room-temperature compression tests. A hot deformation equation is given to characterize the dependence of peak stress with temperature and strain rate. A cold deformation equation is given to characterize the dependence of peak stress. Comparing the results of the high-temperature and room-temperature deformations of the GH4169 alloy indicated that hot deformation is sensitive to both temperature and strain rate, while the cold deformation is sensitive to strain. At room-temperature deformation conditions, for true strain ≈0.2, the dynamic recrystallization nucleates and grains refine.

Microstructure and high temperature compressive deformation in lightweight open cell titanium foam

Ti-foam of varying relative densities has been synthesis through the PM route using ABC as a space holder. Microstructure, cell size and cell wall were evaluated. The compressive deformation of Ti-foams samples with different relative densities was conducted at different temperatures. The yield stress, elastic modulus, energy absorption increases with increasing relative density and also decrease with increase testing temperature. Densification strain decreases with increasing relative density and testing temperature. The micro shear bands visible when deformed at 400–600 °C whereas at lower temperatures foam crumbled. It is due to improved ductility at a higher temperature.

Effect of Zener–Hollomon Parameter on High-Temperature Deformation Behaviors of Mg–6Zn–1.5Y–0.5Ce–0.4Zr Alloy

High-temperature compressive deformation behaviors of Mg–6Zn–1.5Y–0.5Ce–0.4Zr alloy were investigated at temperatures and strain rates ranging from 523 to 673 K and from 0.001 to 1 s−1, respectively. The studied alloy was mainly composed of α-Mg, Mg3Zn6Y (I phase), Mg–Zn–Ce and Mg3Zn3Y2 (W phase). The constitutive equation of Mg alloy was obtained, and the apparent activation energy (Q) was determined as 200.44 kJ/mol, indicating that rare earth phase increases the difficulty of deformation. The work hardening involves three stages: (1) linear hardening stage; (2) strain hardening stage; and (3) softening and steady-state stage. During these three stages, the dislocation aggregation and tangling, dynamic recovery and recrystallization occur sequentially. To characterize the dynamic recrystallization (DRX) volume fraction, the DRX kinetics was investigated using the Avrami-type equation. The deformation mechanism of magnesium alloy under different Zener–Hollomon parameter (Z) value conditions was also studied. At high Z values and intermediate conditions, dislocations rapidly generate and pile up in the alloy. Recrystallization is hardly seen at this time. At low Z condition, the DRX occurs in the alloy.

Room and high-temperature mechanical properties of ZrB2-based composite alloyed with Ti and refractory metal Nb

ZrB2 and ZrB2-based composites have extensive applications; however, their application is hindered by their low fracture toughness at room temperature. A ZrB2/(NbTi) composite with 60 wt% ZrB2 was densified to 97.1% through hot-pressing sintering at 1600 °C under 30 MPa. The phase, microstructure, and room and high-temperature (800–1200 °C) mechanical properties of the composite were investigated. The composite mainly consisted of a (Ti,Nb,Zr) solid solution (ss), Nb-rich (Ti,Nb)B, Ti-rich (Nb,Ti)B, and ZrB2. The room-temperature fracture toughness of the composite was up to 6.9 MPa·m1/2 due to crack bridging, crack defection, and pull-out toughening mechanisms. The high temperature deformability of ZrB2/(NbTi) improved as the test temperature increased from 800 °C to 1200 °C due to the plastic rheological behaviour of the ductile (Ti,Nb,Zr)ss phase and the localised temperature rise. The room and high-temperature compressive deformation processes and failure mechanisms were discussed in detail.

Constitutive Equation and Hot Processing Map of Mg-16Al Magnesium Alloy Bars

A Gleeble-2000D thermal simulation machine was used to investigate the high-temperature hot compression deformation of an extruded Mg-16Al magnesium alloy under various strain rates (0.0001–0.1 s−1) and temperatures (523–673 K). Combined with the strain compensation Arrhenius equation and the Zener–Hollomon (Z) parameter, the constitutive equation of the alloy was constructed. The average deformation activation energy, Q, was 144 KJ/mol, and the strain hardening index (n ≈ 3) under different strain variables indicated that the thermal deformation mechanism was controlled by dislocation slip. The Mg-16Al alloy predicted by the Sellars model was characterized by a small dynamic recrystallization (DRX) critical strain, indicating that Mg17Al12 particles precipitated during the compression deformation promoted the nucleation of DRX. Hot processing maps of the alloy were established based on the dynamic material model. These maps indicated that the high Al content, precipitation of numerous Mg17Al12 phases, and generation of microcracks at low temperature and low strain rate led to an unstable flow of the alloy. The range of suitable hot working parameters of the experimental alloy was relatively small, i.e., the temperature range was 633–673 K, and the strain rate range was 0.001–0.1 s−1.

The effect of addition of Sn to copper on hot compressive deformation mechanisms, microstructural evolution and processing maps

The high-temperature compressive deformation behavior of a Cu-10wt.% Sn solid solution alloy was studied in the temperature range of 843–993K and in the strain rate range of 10−3 – 10s−1 and the relationships among the flow stress, strain rate and temperature were determined. Based on the data obtained from the compression tests, the deformation mechanism was identified, and the processing maps were constructed. The Cu-10Sn alloy exhibited solute drag creep at low strain rates and high temperatures and power law breakdown (PLB) at high strain rates and low temperatures. In the processing maps, above the temperature of 933K, the alloy did not show flow instability up to a high strain rate of 10s−1 and showed high power dissipation efficiencies (31–35%) even at the very high strain rate of 10s−1. Furthermore, at 993K, the fraction of dynamically recrystallized grains after compressive deformation was as high as 0.83 at 10s−1. These results indicate that the Cu-10Sn alloy exhibits a significantly better hot workability and a higher quality of post-deformation microstructures compared to the pure Cu where dislocation climb creep is the main deformation mechanism. Continuous dynamic recrystallization occurred at 843K, while discontinuous dynamic recrystallization occurred at 993K. Comparison of the current results with the previous work on the Cu-4.9Sn alloy indicates that the increase of Sn concentration in Cu matrix extends the regime of solute drag creep and delays the onset of PLB to a lower temperature and a higher strain rate.

Constitutive Behavior of an AA4032 Piston Alloy with Cu and Er Additions upon High-Temperature Compressive Deformation

Aluminum piston alloys of the AA4032 type are produced by direct-chill (DC) casting and subsequent forging; therefore, it is important to understand their thermomechanical behavior. In recent years, it was shown that additions of Cu and Er could improve mechanical properties of these alloys at room and high temperatures. In this work, we studied the constitutive behavior of AA4032-type alloys with and without Cu and Er additions. The experimental true stress–true strain curves were obtained by compression tests under various temperatures [683 K to 723 K (410 °C to 450 °C)] and strain rates (0.01 to 10 s−1) to determine constitutive parameters [strain-rate sensitivity, activation energy, and Zener–Hollomon (Z) parameter] for the hot deformation behavior of AA4032-type piston alloys with and without additions of Cu and Er. The flow stress decreased with increasing deformation temperature and decreasing strain rate. The results also showed that increasing the Cu content increased the flow stress over the applied range of deformation conditions due to solid-solution strengthening and the formation of primary Si particles, which led to an increase in the activation energy during hot deformation. Moreover, the main microstructural damage in the AA4032 alloy with 3.5 pct Cu was predominantly due to the cracking of primary Si particles. Additions of 0.4 pct Er and 3.5 pct Cu lower the activation energy of deformation, Q, as compared to the base alloy and the alloy with 3.5 pct Cu. The microstructures in the deformed specimens consisted of subgrains, recrystallized grains, and fine eutectic phases. The alloys containing Er demonstrated more polygonized grains at a low strain rate than the alloys without Er, indicating that Er hindered recrystallization development. The peak stress of the AA4032 alloy with 3.5 pct Cu alloy was higher than for the base AA4032 alloy and for the AA4032 alloy with 3.5 pct Cu and 0.4 pct Er additions, which was attributed to the prevalence of the work-hardening mechanism over the softening mechanism.

Basal texture formation behavior of M1 magnesium alloy during high-temperature compression deformation

Understanding the formation behavior of basal texture is important for improving formability. Many researchers found that deformation condition was an important factor in order to texture control on AZ system magnesium alloy. In case of M1 magnesium alloy has been investigated in texture formation resulting from grain size manipulation by precipitation, but there seems no studies on the texture development during high temperature on M1 magnesium alloy by deformation condition. In this study, microstructure evolution and texture formation behavior is investigated under various deformation conditions in M1 magnesium alloy. In order to make the same initial conditions, M1 magnesium ingot was rolled at 673K with a rolling reduction of 30%. Uniaxial compression test specimens were machined in such a way that the compression plane was parallel to the rolling plane, and subsequently annealed at 823 K for 1h. Uniaxial compression tests were carried out at 673K and 723K under a strain rate of 5.0x10−2s−1up to a strain of -1.0. EBSD measurement was performed for observation of crystal orientation distribution. As a result, occurrence of the dynamic recrystallization was confirmed. The position of maximum axis density of the texture and its intensity were varied depending on deformation conditions.

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.

Study on the Constitutive Equation of High-Temperature of High-Elastic Cu-20.0Ni-5.0Sn-0.25Zn-0.22Mn Alloy

The high-elastic Cu-20.0Ni-5.0Sn-0.25Zn-0.22Mn alloy was designed and prepared using a 830°C/2h+850°C/2h dual-stage homogenization annealing process. The true stress-strain curves of well annealed Cu-20.0Ni-5.0Sn-0.25Zn-0.22Mn alloy were plotted as a function of compressive temperature and strain rate. The results showed that the stage division of thermal compression deformation is temperature dependent, which involves work hardening, dynamic recovery and recrystallization stages. The maximum value of the true stress increases as the strain rate gets larger, but decreases as the deformation temperature rises. The high temperature compression deformation process of the alloy is a thermal activated process, and the corresponding constitutive equation of the true stress-strain is established.

Constitutive modeling for high temperature compressive deformation of non-oriented electrical steel

Abstract A material mechanical model provides basic data for numerical simulation and technological optimization during the forming process. In this paper, the flow behavior of the hot compressive deformation 0.3 wt.-% Si non-orientation electrical steel were investigated by thermal simulation tests, and a constitutive model was built based on a new modeling method. The thermal simulation tests conducted on a Gleeble 1500 thermo-mechanical simulator over a range of temperatures from 750 to 1050 °C and strain rates from 0.1 to 10 s−1. To predict the hot deformation process of the silicon steel, a constitutive model based on the multiple regression method was developed. Prediction results showed that the proposed model can track deformational behavior accurately. The model was applied to finite element (FE) simulation, and the FE calculation results matched the industry production data satisfactorily.

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 <0001> 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)<100> and (0001)<110> during deformation.

Effect of Stress Relieving Heat Treatment on the Microstructure and High-Temperature Compressive Deformation Behavior of Ti-6Al-4V Alloy Manufactured by Selective Laser Melting

This study aims to investigate the effect of stress relieving heat treatment on the microstructure and high-temperature compressive deformation behavior of the Ti-6Al-4V alloy, manufactured by selective laser melting. Initial microstructural observation confirmed elongated prior β grains in the building direction of both specimens (as-fabricated and heat-treated specimens). Along with such, the as-fabricated specimen only featured α′-martensite phase, while the heat-treated specimen featured α′-martensite and some α and β phases. Compression tests carried out at room temperature gave yield strengths of 1365 and 1138 MPa for the as-fabricated and heat-treated specimens, respectively. Such values are similar or greater than those of commercial wrought materials. The compressive fracture strain significantly increased after heat treatment. There was a general tendency of reducing yield strength as compressive temperatures increased. At temperatures greater than 700 °C, the as-fabricated and heat-treated specimens achieved similar strength. Microstructural observation after deformation confirmed that the initial microstructure was retained up to temperatures of 500 °C. At 700 °C or greater, both specimens showed drastic microstructural evolution.

High-temperature deformation and processing maps of Zr-4 metal matrix with dispersed coated surrogate nuclear fuel particles

Abstract High-temperature compression deformation of a Zr-4 metal matrix with dispersed coated surrogate nuclear fuel particles was investigated at 750 °C–950 °C with a strain rate of 0.01–1.0 s−1 and height reduction of 20%. Scanning electron microscopy was utilized to investigate the influence of the deformation conditions on the microstructure of the composite and damage to the coated surrogate fuel particles. The results indicated that the flow stress of the composite increased with increasing strain rate and decreasing temperature. The true stress–strain curves showed obvious serrated oscillation characteristics. There were stable deformation ranges at the initial deformation stage with low true strain at strain rate 0.01 s−1 for all measured temperatures. Additionally, the coating on the surface of the surrogate nuclear fuel particles was damaged when the Zr-4 matrix was deformed at conditions of high strain rate and low temperature. The deformation stability was obtained from the processing maps and microstructural characterization. The high-temperature deformation activation energy was 354.22, 407.68, and 433.81 kJ/mol at true strains of 0.02, 0.08, and 0.15, respectively. The optimum deformation parameters for the composite were 900–950 °C and 0.01 s−1. These results are expected to provide guidance for subsequent determination of possible hot working processes for this composite.

High temperature deformation behavior of carbon-containing FeCoCrNiMn high entropy alloy

High temperature compressive deformation behaviors of a carbon-containing FeCoCrNiMn high entropy alloy (HEA) was investigated at temperatures ranging from 700 °C to 1000 °C, and strain rates from 0.001s−1 to 1s−1. The microstructure mainly consists of fcc solid solution. The data obtained from the flow curves was employed to develop the constitutive equation, and the apparent activation energy (Q) was determined to be 385.43 kJ/mol. The size of the dynamically recrystallized grains decreased with the increasing value of Zener-Hollomon (Z) parameter. At high Z condition, dislocation cross slip can act as the main deformation mechanism. At intermediate Z condition, dislocation cross slip accompanied by discontinuous dynamic recrystallization (dDRX) becomes the main deformation mechanisms. At low Z condition, continuous dynamic recrystallization (cDRX) becomes the dominant softening mechanism. Nano carbides can be precipitated at intermediate Z and low Z condition, which prevent grain from growing up and promote the nucleation of DRX.