Drop In Flow Stress Research Articles

Electroplasticity mechanism of Ti2AlNb alloys under hot compression with the application of a lower electric current

In this study, a lower electric current (1.0–2.0 A/mm2) was applied during hot compression of Ti2AlNb alloys, and the mechanical response, microstructure evolution, and electroplasticity mechanism were investigated. The results showed that the maximum flow stress drop could reach 18.7 % after applying a lower electric current of 2.0 A/mm2, which confirms the existence of electroplasticity. The stress drop increased with increasing electric current density. However, the flow stresses of the samples in the isothermal compression test and those subjected to a 1.0 A/mm2 electric current compression test were similar, indicating that there is a threshold value for the electroplasticity effect on flow stress. The lower strain hardening rate caused by the electric current confirmed the electroplasticity effect, promoting the softening effect. Additionally, the lower average activation energy Q, affected by the electric current, implied the improvement of the deformability of the alloy due to the deformation mechanism of dynamic recovery (DRV), dynamic globularization, or dynamic recrystallization (DRX). The gradual reduction of dislocation density with increasing electric current density resulted in the stress drop, which can be ascribed to the directional drifting electrons colliding with dislocations, which promoted the movement of dislocations by arranging the dislocations in parallel. The local high temperature induced by the local Joule heating effect at the O lamella had a strong promoting effect on the globularization of the O lamella by producing uniform lattice distortion/local strain at the O/B2 interface. With increasing furnace temperature, the drifting electrons accelerated the transformation of LAGBs to HAGBs which promoted the appearance of dynamic recrystallization grains.

Hydrogen Embrittlement of 27Cr-4Mo-2Ni Super Ferritic Stainless Steel.

The effect of hydrogen content on the deformation and fracture behavior of 27Cr-4Mo-2Ni super ferritic stainless steel (SFSS) was investigated in this study. It was shown that the plasticity and yield strength of SFSS were very susceptible to hydrogen content. The introduction of hydrogen led to a significant decrease in elongation and a concurrent increase in yield strength. Nevertheless, a critical threshold was identified in the elongation reduction, after which the elongation remained approximately constant even with more hydrogen introduced, while the yield strength exhibited a monotonic increase with increasing hydrogen content within the experimental range, attributed to the pinning effect of the hydrogen Cottrell atmosphere on dislocations. Furthermore, the hydrogen-charged SFSS shows an apparent drop in flow stress after upper yielding and a reduced work hardening rate during the subsequent plastic deformation. The more hydrogen is charged, the more the flow stress drops, and the lower the work hardening rate becomes.

Portevin-Le Chatelier characterization of annealed Al-Mg alloy sheets with different Mg contents

The stress-strain flow curves of solid solution treated and annealed Al-(2.86-9.41)Mg aluminum alloy sheets were investigated during tensile process at room temperature at a strain rate of 1 × 10−3 s−1, in order to reveal the effect of solute Mg atoms and β-phase nanoparticles in the α-Al matrix on their Portevin-Le Chatelier (PLC) characteristics. The results show that with the increase of Mg contents of alloys, the concentration of solute Mg atoms and the volume fraction of β-phase nanoparticles in the α-Al matrix of the annealed alloy sheets increase. The β-phase nanoparticles promote the PLC effect during the tensile process, causing the increase of stress drop amplitude Δσ of the tensile curves of the alloy sheets. However, the β-phase nanoparticles have little influence on the strain period ΔεTmax of rectangular waves. The flow strain difference Δεc−σ between the yield point and the beginning of PLC effect decreases monotonically from 5.4 × 10−4 to 5 × 10−5 as the Mg contents of alloy sheets increase from 2.86 wt.% to 9.41 wt.%. The strain period ΔεTmax of the rectangular waves corresponding to the high flow stress and stress drop amplitude Δσ obtained for the serrated stress-strain curves of the alloy sheets gradually increase with the increasing Mg contents of alloy sheets.

Characterization of stress drop and strain localization for titanium alloy subjected to electrically-assisted tension

The stress drop and strain localization behaviors of Ti–6Al–4V titanium alloy under the action of single pulse were investigated using electrically-assisted (EA) tension tests in this study. It is found that the flow stress drop gradually increases with the increase of current density and pulse width during EA tension. The digital image correlation (DIC) technology was adopted to analyze the strain distribution evolution and fracture regulation in EA micro-tension process. It turn out that the EA tensile sample will suddenly form two new intersecting high-strain bands at the moment of applying a pulse. With the increase of strain, the two high-strain bands converge toward the center and gradually evolve into a crossed localized flow zone, which makes the EA tensile sample exhibit a high local plastic deformation compared with room temperature tension. Furthermore, with the increase of current density, the temperature gradient in the tensile direction of the sample increases gradually, resulting in the narrowing of localized flow zone. The transformation of the localized flow zone eventually leads to the increase of fracture angle and the formation of a sawtooth shape fracture morphology. Finally, a material flow model for the single-pulse EA tension process was established. The calculation results show that about 11 % of the stress drop comes from the contribution of non-thermal electroplastic, the main mechanism of stress drop is thermal softening and thermal expansion induced by Joule heat during EA tension.

Dynamic phase transformation driven microstructure and texture development during deformation of Zr-2.5wt.%Nb in α+β phase field

This work demonstrates and explains how, during the hot deformation of a Zr alloy in the two-phase field, the texture developed in the α phase is influenced by that developed in the β phase. For this Zr-2.5wt.%Nb alloy was hot compressed in the α+β phase field (700, 750 and 800°C) at 0.1 s−1 to a true strain of 1.1. The microstructure and texture were characterized using scanning electron microscopy and electron backscatter diffraction. The flow curves showed a sharp drop in flow stress at ε≈0.01 due to plastic deformation induced α→β phase transformation. At 700°C, α-Zr developed 〈21¯1¯3〉 parallel to compression axis (||CA) (as is commonly observed in α-Zr system), whereas at 750 and 800°C 〈21¯1¯0〉||CA formed. At all studied temperatures, β-Zr developed {001}〈110〉 and {111}〈110〉 texture components that were shown to be dependent on the elongated morphology of the α-Zr grains and not on the α-Zr texture. From experimental observations and thermodynamic calculations of the free energy changes in absence and presence of stress, it was shown that the formation of 〈21¯1¯0〉α−Zr||CA occurred by migration of β-Zr into 〈21¯1¯3〉α−Zr followed by the reverse β→α transformation (through Burgers orientation relationship) driven by low flow stress in 〈21¯1¯0〉α−Zr and low Nb content in the transforming β-Zr. It was concluded that the presence of β-Zr with 〈001〉||CA and 〈111〉||CA is a necessary condition for the formation of 〈21¯1¯0〉||CA in α-Zr. In addition, temperature promotes the development of 〈21¯1¯0〉α−Zr through enhanced boundary mobility of β-Zr into harder α-Zr.

Decoupling electroplasticity by temporal coordination design of pulse current loading and straining

Multi-mechanism coupled electroplasticity (EP) has not been fully elucidated yet due to the difficulty in eliminating thermal effect, although isothermal, air-cooled, and cryogenic methods are usually used, there are different heating histories from electrically-assisted deformation. The 0–7% pre-strained Ti–6Al–4V alloy is taken as the case material. Based on the two different characteristics of the time-accumulation of thermal effect and the instantaneous nature of the athermal effect, a comparative study is conducted by designing two temporal coordination methods of pulse current and straining, viz., asynchronous loading with high-energy current (ALHC) and synchronous loading with low-energy current (SLLC), where the thermal and athermal effects are highlighted by different loading times, loading and unloading moments of pulse current of different magnitudes. Under ALHC condition, the decreasing yield strength and increasing elongation of the 7% pre-deformed material are observed with increasing current density and loading times, and stress reduction up to 20.7% for yield strength and ductility recovery of maximal 99.1% for elongation are obtained for 14.0 A/mm2 and loading three times. Moreover, stage B of the work hardening rate related to dislocation de-pinning disappears, and the TEM shows an annealing effect that the tangled dislocations are annihilated and rearranged by climbing. Thus, the Joule heat-based thermal effect dominates this condition. Under SLLC condition, the loading and unloading of pulse current of 2.81 A/mm2 in the plastic stage result in an instantaneous drop and rebound in flow stress and work hardening rate (stage B exists), respectively, and are accompanied by the negligible instantaneous temperature rise, while loading at the elastic stage, the overall flow stress and work hardening rate is decreased. It is concluded that the athermal effect can lower the dislocation phonon drag effect and the deformation activation energy, and change the athermal atomic state and dislocation slip mode, which dominates the varied flow stress and elongation. A dislocation dynamics-based physical model is developed by taking into account phonon drag, diffusion activation energy, and deformation activation energy to account for the thermal and athermal effects on dislocations, providing a self-consistent explanation of the above behaviors and mechanisms of the flow stress and ductility under ALHC and SLLC conditions.

Effects of process parameters and loading direction on the impact strength of additively manufactured 18%Ni-M350 maraging steel under dynamic impact loading

The microstructural and damage evolution of 18%Ni M350 maraging steel fabricated by laser-based directed energy deposition (DED) process under dynamic impact loading are investigated in this study. The influence of additive manufacturing (AM) processing parameters, including laser power, powder feed rate, and energy area density (EAD) are discussed. The mechanical testing of the additively manufactured alloy was done using the split Hopkinson pressure bar (SHPB) system. The dynamic impact test was conducted using strain rates ranging from 100 to 4000 s−1. The test was conducted on cylindrical specimens (7 mm diameter and 8 mm long) with axes parallel to the build direction (Z-axis) and perpendicular (X- and Y-axis) to the build direction to evaluate the effects of loading directions on mechanical responses and microstructural evolution in the alloy under the impact loading conditions. The test results revealed that the materials processed using the lowest EAD parameters exhibit the greatest impact strength under dynamic impact loading for all directions. Specimens impacted along the build direction (Z-axis) exhibit a continuous drop in peak flow stress once the strain rates exceeded 2300 s−1 indicating the greatest susceptibility to thermal softening at high strain rates. Strain localization leading to the formation of adiabatic shear bands (ASB) was observed in some specimens. Cracks developed along the ASBs, while some AM-process-related defects, such as the lack-of-fusion, interacted with adiabatic shear bands, promoting cracking inside the shear bands. Despite possessing the highest impact strength, the materials produced by the lowest EAD parameters are the most susceptible to the development of adiabatic shear bands leading to cracking and fracture.

The Effect of Strain Rate on the Tensile Deformation Behavior of Single Crystal, Ni-Based Superalloys

Single crystal Nickel-based superalloys exhibit an anomalous yield point, the yield stress increasing with temperature to a maximum at around 750 ºC. Here, we demonstrate in the alloy CMSX-4 at 750 ºC that, although there is virtually no effect of strain rate on the initial yield point, at slow strain rates a second mechanism can initiate leading to a considerable softening effect. By examining the microstructures of a series of interrupted tests, this is attributed to the initiation of stacking fault shear after the operation of a secondary slip system. Using high-resolution TEM, the dislocation structures are shown to be identical in both structure and in the segregation of Co, Cr, and W, to those observed during creep deformation of single crystal alloys, although the conformation of the dislocations and faults differs from that observed during creep. This drop in flow stress at low strain rates is not observed in the alloys TMS138A and SRR99, in the former case, the improved creep resistance of this fourth-generation alloy would require a much slower strain rate to match the creep rate achievable at this temperature.

Effect of Pulsed Current-Assisted Tension on the Mechanical Behavior and Local Strain of Nickel-Based Superalloy Sheet

Electrically assisted (EA) forming is a plastic forming technique under the coupling action of multiple energy fields, such as force field, temperature field, and electric field. It is suitable for the forming of difficult-to-deform materials such as nickel-based superalloys. In this paper, uniaxial tensile tests on nickel-based superalloy sheets were carried out using the pulsed current assisted with different parameters. The experimental results show that the flow stress of the material decreased with the increase in the current density under a high-frequency pulsed current, and the Joule heating effect explains the flow stress drop. In the pulsed current application process, the different types of Portevin-Le Chatelier phenomena appeared with the increase in the current density. The decrease in elongation assisted by the pulsed current was explained by analyzing the inhomogeneity of the maximum Joule heating temperature distribution. In addition, the digital image correlation (DIC) analysis was used to analyze the local strain behavior of the pulsed current-assisted tensile process. Under the application of a high-frequency pulse current, the specimen exerted an inhomogeneous temperature increase and local hot pressing stress, which resulted in the inhomogeneous distribution of the local strain.

Dynamic transformation of a near alpha high-temperature titanium alloy during hot deformation

The rapid drop of peak flow stress in the initial stage of hot compression experiment was found to be related to the occurrence of dynamic transformation from alpha phase (hcp) into beta phase (bcc) of a near α high-temperature titanium alloy. In order to predict the flow stress at all strain, the dynamic recovery (DRV) model and the Back-Error Propagation (BP) neural network architecture were established and comprehensively utilized to characterize the flow stress, which exhibited high accuracy in tracking the flow behavior at different deformation parameters. The variation of peak flow stress at initial stage of hot compression indicated that the rapid drop extent of peak value increased with the rise of deformation temperature, the decrease of strain rate and the increase of strain. It was worth noting that the dynamic transformation evolution in the microstructure exhibited the consistent variation of peak flow stress with different deformation parameters. The high-magnification microstructure analysis indicated that the dynamic transformation was accomplished by the immigration of α/β interface and the penetration of beta phase into alpha phase from edge to inside, all of which were related to the dislocation motion. The experimental result proved that the dynamic transformation was the dominant factor resulting in the rapid drop of peak flow stress at the initial stage of hot deformation.

High-temperature deformation behavior and microstructural evolution of NbZrTiTa refractory high entropy alloy

The hot deformation behaviors and microstructural evolution of an equiatomic NbZrTiTa refractory high entropy alloy (RHEA) were studied by using isothermal compression tests in a range of temperatures (900 °C∼1200 °C) and strain rates (10−3 s−1∼1 s−1). A category of Arrhenius power law relationship was constructed and the activation energy was calculated to be 336–403 kJ mol−1 throughout the strain. The dislocation piling-up and kink bands found in local microstructural areas at low temperatures and high strain rates contributed to intense strain hardening and subsequent strain softening. As the temperature increased and the strain rate decreased, a sharp drop in flow stress was observed after the peak stress. This may be explained by dislocations pinned by short-range ordering (SRO) structures being unlocked. The higher dislocation density and newly emerging fine grains near deformed grain boundaries suggested that the dynamic recrystallization (DRX) was responsible for the continuous flow softening. Discontinuous DRX (DDRX) was the main DRX mechanism in this work, however, the isolated equiaxed grains in initial grains and large cumulative misorientation along the interior of the deformed grains were also found at the high temperatures and low strain rates, which demonstrated that the continuous DRX (CDRX) occurred.

Stacking fault induced hardening and grain size effect in nanocrystalline CoNiCrFeMn high-entropy alloy

A broad variation of stacking fault energy (SFE) in high entropy alloys (HEAs) gives rise to rich deformation mechanisms and unique mechanical properties of HEAs. In this paper, we aim to reveal the interplay between grain boundaries and stacking faults in governing the strength and flow stress of CoNiCrFeMn HEA. We carried out atomistic simulations for the tension of polycrystalline CoNiCrFeMn HEA of different grain sizes from 3.0 to 48.6 nm at different temperatures. The tensile flow stress of the HEA follows the traditional Hall–Petch (HP) relation till grain size is down to 15.0 nm. Massive stacking faults contribute to the extra hardening and render a rather gradual drop of flow stress with increasing grain size: In the regime governed by HP relation, partial dislocations emitting from grain boundaries are primarily leading partials; and resulted stacking fault (SF) can serve as barriers to dislocation gliding on intersecting planes. This mild hardening mechanism complements strong hardening from grain boundaries. We expect SF induced hardening could be general in polycrystalline HEAs. The findings reported here may provide a basis and engineering guidance for strengthening and toughening the design of a broad range of HEAs characterized by a wide spectrum of SFEs.

Portevin-Le Chatelier Characterization of Quenched Al-Mg Alloy Sheet with Different Mg Concentrations.

In the present study, the PLC characteristic parameters and DSA mechanism of Al-(2.86~9.41) Mg alloy sheets were investigated during tensile testing at room temperature with a tensile rate of 1 × 10−3 s−1. On the basis of the solution Mg concentrations in the α-Al matrix, the initial vacancy concentration, the second-phase particle configuration and the recrystallized grain configuration are almost the same by quenching treatment. The results show that the type of room-temperature tensile stress–strain curves of quenched Al-(2.86~9.41) Mg alloy sheets varied according to the Mg content. The type of stress–strain curve of the Al-2.86 Mg alloy sheet was B + C, while the type of stress–strain curve of the Al-(4.23~9.41) Mg alloy sheets was C. When the quenched Al-(2.86~9.41) Mg alloy sheets were stretched at room temperature, the strain cycle of the rectangular waves corresponding to the high stress flow and stress drop amplitude on the zigzag stress–strain curve of alloy sheets increased with increasing the Mg content. Moreover, the strain cycle of and on the stress–strain curve of alloy sheets increased gradually with increasing tensile deformation. The yield stress of quenched Al-(2.86~9.41) Mg alloy sheets increased gradually with increasing the Mg content. Moreover, the critical strain corresponding to yield stress and the critical strain corresponding to the occurrence of the PLC shearing band of alloy sheets both increased with increasing the Mg content. However, the difference in flow strain value between and of alloy sheets decreased gradually with increasing the Mg content.

Hot deformation characteristics of Ti-6Al-4V

Abstract The flow behavior and hot deformation mechanisms of Ti-6Al-4Vin both β and (α + β) phase regions have been studied by compression tests in the temperature range 750 – 1100 °C and strain rate range 0.05 –15 s –1. The flow curves displayed discontinuous yielding at temperatures above 850 °C and high strain rates, typically 5 and 15 s–1. Flow oscillations were also observed under such conditions. The relative discontinuous flow stress drop increased with increasing temperature in the (α + β) phase region and reached a steady state in the β phase region. The discontinuous yielding is attributed to the sudden increase in the mobile dislocation density occurring due to the activation of β grain boundary sources during hot deformation. The apparent activation energy estimated using the standard kinetic analysis is about 246 kJ/mol in the β region and 621 kJ/ mol in the (α + β) region while the strain rate sensitivity values are 0.34 and 0.18, respectively. The mechanism in the β region has been suggested to involve grain boundary sliding and dynamic recovery of the β phase while in the (α + β) region a transient mechanism, involving dynamic recovery followed by post deformation recrystallization, has been proposed.

Quasi-static and dynamic behavior of additively manufactured lattice structures with hybrid topologies

When different unit cell topologies with distinct mechanical behavior (e.g. bending vs stretching dominated) are incorporated into a single hybrid lattice structure (LS), questions arise about the resolution of local stresses within the struts and how localized states of strain as a result govern the global response of the structure. To understand the mechanics of hybrid LS, this study uses a combination of experimental and modeling data to investigate the relationship between localized states of stress with the global behavior of hybrid additive manufactured lattice structures (AMLS) under different loading directions and strain rates. The hybrid AMLS in this study consist of two different unit cell topologies stacked in alternating rows, with loading directions identified with respect to this topology stacking. It is shown that the loading direction influences the mechanical behavior, as the flow stress of the hybrid AMLS is 7%–10% lower when loaded in the stacking direction than when loaded in the transverse direction. This flow stress decrease is due to a smaller number of structural elements supporting the loading and tensile failure of horizontally-manufactured struts in the stacking direction. The strain rate also influenced the mechanical behavior of the AMLS, as irrespective to the loading direction, for all hybrid AMLS, the first peak stress after static equilibrium is 5%–10% higher under dynamic loading compared to quasi-static loading. Additionally, it is shown that the collapse mechanisms are influenced by the order of the topology stacking. Structural shear band formation, which leads to up to a 60% drop in flow stress under dynamic loading of the hybrid AMLS, can be inhibited by separating adjacent rows of shear band-forming topologies with a row of unit cells of a topology which does not form shear bands. Ultimately, it was determined that the performance of these layered structures is limited by the weakest topology. Even under transverse loading, where the first peak stress approaches that of the stronger topology, the magnitude of the subsequent decrease in flow stress is generally more in line with that of the weaker topology.

Rapid dynamic transformation in the initial stage of hot deformation of a near alpha titanium alloy

The peak flow stress of a near alpha high temperature titanium alloy exhibits a special rapid drop behavior at low strain during hot compression. The experimental result indicates that this rapid drop of peak flow stress is related to the rapid dynamic transformation from alpha phase into beta phase which is induced by the deformation at elevated temperature. Both peak flow stress and the dynamic transformation change with different hot deformation parameters, and the drop of peak flow stress keeps almost consistent variation with the evolution of dynamic transformation observed from the microstructural morphology. The higher deformation temperature and the lower strain rate with the small increase of strain are beneficial to accelerate the dynamic transformation and the drop of peak flow stress. The dynamic transformation is mainly controlled by the immigration of alpha/beta interface shrinking from edge to center of equiaxed alpha phase or the penetration of beta phase into alpha phase from edge to inside.

A Novel Flow Model of Strain Hardening and Softening for Use in Tensile Testing of a Cylindrical Specimen at Room Temperature.

We develop a new flow model based on the Swift method, which is both versatile and accurate when used to describe flow stress in terms of strain hardening and damage softening. A practical issue associated with flow stress at room temperature is discussed in terms of tensile testing of a cylindrical specimen; we deal with both material identification and finite element predictions. The flow model has four major components, namely the stress before, at, and after the necking point and around fracture point. The Swift model has the drawback that not all major points of stress can be covered simultaneously. A term of strain to the third or fourth power (the “second strain hardening exponent”), multiplied and thus controlled by a second strain hardening parameter, can be neglected at small strains. Any effect of the second strain hardening exponent on the identification of the necking point is thus negligible. We use this term to enhance the flexibility and accuracy of our new flow model, which naturally couples flow stress with damage using the same hardening constant as a function of damage. The hardening constant becomes negative when damage exceeds a critical value that causes a drastic drop in flow stress.

Influence of deformation parameters and network structure to the microstructure evolution and flow stress of TiBw/Ti64 composite

Titanium matrix composites (TMCs) play important roles in the weight reduction of the modern aero-space industry due to the excellent combination of strength and ductility. Especially, titanium matrix composites with network architecture have drawn much attention in recent years. To better understand the influence of deformation temperature, strain rate and the network size over the microstructure evolution and the flow stress of network structured TMCs, 8 vol.% TiBw/Ti64 composites with network sized 65 μm, 110 μm and 150 μm were prepared for thermal compression test. The results showed that the decrease in deformation temperature and the increase of the strain rate will prompt the dynamic recrystallization process, thereby producing refined equiaxed α grains. Multiple changes were observed accompanying the decrease of network size, including the refinement of the deformation microstructure, the drop of compressive flow stress, as well as the decrease of the texture intensity. It was also found that, the texture of specimens deformed in β region was inherited from the texture of body centered cubic (BCC) β phase through β→α transformation, abiding by Burgers relationship. Moreover, preference in variants selection during β→α transformation was observed, which is an important factor for the formation of texture in β phase deformation.

Effect of hydrogen addition on compression deformation behaviour of Ti–0.3Mo–0.8Ni alloy argon-arc welded joints

The effect of hydrogen addition on compression deformation behaviour of Ti–0.3Mo–0.8Ni alloy argon-arc welded joint has been investigated. Evolution mechanism of hydrogen-induced flow stress was discussed in detail. The results show that with increasing hydrogen content, the stretching and bending extent of fully lamellar microstructures including α lamellas and acicular hydride continued to increase, the morphology of dynamic recrystallization (DRX) grains tended to change from approximately equiaxed to large lamellar shape, and the quantity of DRX grains and recrystallization degree of grains increased obviously. A large number of dislocations concentrated in the vicinity of the hydride. Steady stress was decreased continuously with increasing hydrogen content, while peak stress of the hydrogenated 0.12 wt.% H weld zone was decreased to the minimum value and then increased slowly. A slight decrease in flow stress of the hydrogenated 0.05 wt.% H weld zone was caused by limited increase in the volume fraction of softer β phase. Hydrogen-induced DRX of α phase and improved dislocation movement by strong interaction between the hydride and dislocation directly resulted in a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone. Solute hydrogen also finitely contributed to a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone by promoted local softening, which induced continuous DRX and more movable dislocations to participate in slipping or climbing. The reinforcement effect and plastic deformation of the hydride and solution strengthening of β phase induced by solute hydrogen finally led to the increase in flow stress of the hydrogenated 0.21 wt.% H weld zone in its true strain range from 0 to 0.36.

Hot deformation studies of AISI 1035 steel using thermo mechanical simulator

Uni-axial hot compression tests were conducted in the temperature range of 900–1100 °C and strain rate range of 0.2–20 s−1 using thermo-mechanical simulator in order to study the effect of forging conditions viz. temperature and strain rate on flow behaviour of AISI 1035 medium carbon steel. The results indicate that both the parameters have profound effect on flow stress. The curves of true stress strain revealed that flow stress increases with lowering of forging temperature and with an increase in strain rate. At all deformation conditions flow softening phenomena was observed which were reflected by a peak followed by a drop in flow stress with further straining. Flow softening was predominantly due to dynamic recrystallization at lower strain rates of 0.2/s and 2/s. Peak stress shifted towards higher strain with an increase in strain rate at all deformation temperatures. Experimental data were fitted to Arrhenius-type constitutive equations to find material constants and activation energy. The calculated stress values were compared with the measured ones and they showed very good agreement, which confirm that the proposed deformation constitutive equations could predict an accurate and a precise flow stress value for AISI 1035 steel. The microstructures of the deformed specimens under different deformation conditions were analyzed using optical microscopy.