Development Of Subgrains Research Articles

Temperature dependence of the friction and wear behavior of pure tungsten

In this work, the friction and wear characteristics of rolled pure tungsten were investigated by using atomic force microscope (AFM) and field emission scanning electron microscope (SEM) with electron backscatter diffraction (EBSD) characterization techniques. A ductile to brittle transition (DBT) related frictional wear behaviors have been discovered. The results indicated that the coefficient of friction maintains an almost constant value of 0.45 at low temperatures (≤ 400 °C), whereas it consistently decreases at 600 °C due to the generation of a surface oxide. The wear rate varies with temperatures and reaches a maximum at 200 °C due to the transition of the tungsten matrix from brittleness to pseudoplasticity, which leads to severe adhesive wear and large mass loss. In addition, the evolution of sub-grains underneath the friction layer and Vickers microhardness were evaluated as well. This work provides insight into understanding the relationship between temperatures, microstructure and the frictional properties of tungsten materials, and thus provides guidance for improving frictional wear behaviors in tungsten materials.

Hot deformation behavior and dynamic recrystallization of 2195 Al–Li alloy with various pre-precipitation microstructures

In this work, 2195 Al–Li alloys with various precipitation microstructures were obtained by homogenization treatment followed by air-cooling (AC), discontinuous cooling (DC), and furnace-cooling (FC), and then tested by hot compression at different temperatures. The results show that the flow stresses of all specimens decrease with temperature and the peak stresses of AC, DC and FC specimens decrease in order at the same temperature. For FC samples, coarse pre-precipitates diminish the deformation resistance due to the reduction of solid solution strengthening and precipitation strengthening. Dynamic softening at low temperatures is significantly greater than that at high temperatures, except for the anomalous softening of the FC specimen at 520 °C due to stress release by cracks. At 370–420 ​°C, the dynamic softening of the AC specimen is more significant than the other samples, resulting from dynamic precipitation and precipitate coarsening. Furthermore, there is considerable dynamic recrystallization (DRX) in FC samples and not in AC and DC samples, although their precipitates coarsen to similar levels at low temperatures. This suggests that DRX is associated with the particle-stimulated nucleation mechanism by regularly arranged precipitates. The banded or regularly arranged precipitates divide the Al matrix into multiple confined units, hindering dislocations and (sub)grain boundary movement, and thus promoting the development of sub-grains and DRX.

Evolution of microstructure and changes in hydrogen embrittlement resistance of CLAM steel after long-term aging

To investigate the changes in hydrogen embrittlement (HE) resistance of China Low Activation Martensitic (CLAM) steel during thermal aging, CLAM steels were aged at 550 °C and 600 °C up to 5000 h. The evolution of microstructure, including the evolution of subgrains, the growth of M23C6 carbides and MX carbonitrides, as well as the formation of Laves phase, were carefully characterized. The observed trend revealed an initial increase followed by a subsequent decrease in HE resistance upon prolonged aging durations. The mechanisms for changes in HE resistance were analyzed based on the orientation relationship between precipitates and matrix.

Mechanical properties and microstructure of Al–Mg (5052) alloy processed by equal-channel angular pressing (ECAP) with variation of ECAP routes and heat treatment

Equal-Channel Angular Pressing (ECAP) has become an effective technique of severe plastic deformation designed to produce ultrafine grain metals with improved mechanical properties, such as a good combination of strength and ductility. A report on the effect of ECAP routes on the mechanical and microstructure of commercial 5052 aluminum alloy needs also to be included. This work has been undertaken, in order to obtain the results. In this work, several deformation routes were used to process the Al – Mg (5052) alloy, namely A, Ba, Bc and C. Deformation route A involved repeatedly pushing the sample into the ECAP die without rotation, route Ba was performed by rotating the sample through 90° in alternate directions between each pass, route Bc by rotating the sample 90° in the same sense between each pass and route C by rotating the sample 180° between passes. The addition of the pass number decreases the grain size of ECAP-processed samples when compared to the as-annealed sample. It also confirmed that the microstructure of the 8-pass samples shows a finer grain size than the as-annealed sample. Furthermore, the Bc route (samples rotated in the same sense by 90° between each pass) has been proven to be the most effective deformation route, in order to obtain equiaxed ultrafine grain structure when compared to other deformation routes. This phenomenon takes place due to the continuous deformation in all cubic planes. The restoration after the 4-pass number will lead to the rapid evolution of sub-grains to high-angle grain boundaries, forming equiaxed grains. The characterization of the hardness number also shows that the addition of the ECAP pass number increases the hardness number of 5052 aluminum alloy, where samples processed with the Bc route indicate the highest hardness number at 168.4 HB. Moreover, a similar phenomenon also suggests that the tensile strength of all ECAP deformation routes has comparable values. The effect of heat treatment for samples with the Bc route also shows that 200 °C annealed samples have the highest hardness number and tensile strength when compared to other samples.

Microstructural evolution and formability of Ti−6Al−4V alloy sheet during electropulsing-assisted bending

The electropulsing-assisted bending test was carried out on Ti−6Al−4V alloy sheet with the effective current density of 0−3.2 A/mm2 and duty ratio of 10%−70%. The results show that the bending forming displacement increased from 9.15 to 15.60 mm with increasing effective current density from 0 to 2.4 A/mm2. The crack changed to be shallow and small at the same time. Besides, the springback angle decreased as the effective current density increased at the bending displacement of 8 mm. Duty ratio also affected bending angle, where 30% duty ratio led to the lowest bending angle of 135.0°. The thermal stability temperature increased with increasing effective current density and varied non-monotonically with duty ratio. In addition, grain coarsening, {0001} texture strengthening and sub-grain development were observed during electropulsing-assisted bending. The electropulsing decreased dislocation density and accelerated dislocation rearrangement, the rearranged and piled-up dislocation inside α grains promoted sub-grain structure formation, which improved the formability. The contribution of athermal effect made the low-temperature formability of Ti−6Al−4V alloy comparable to that at high temperature.

Crystal plasticity and fluid availability govern the ability of titanite to record the age of deformation

Here, we study the relationships of titanite-hosting microdomains, intragrain chemical variations, microstructure and fluids with the aim of deciphering the reliability of titanite U–Pb dating to constrain the age of deformation in mylonitic rocks. We investigate these relationships in a post-Variscan amphibolite-facies shear zone developed in the mid-low continental crust (Ivrea-Verbano Zone, Southern Alps, Italy). Quantitative orientation analyses along with textural imaging of titanite are combined with trace-element analyses and U–Pb age dating. Titanite is studied in mm- to cm-scale layered rocks showing compositional variation consisting of alternating ‘amphibole-rich’ (i.e., amphibolites) and ‘clinopyroxene/plagioclase-rich’ domains (i.e., calc-silicates). Titanite from amphibole-rich domains shows predominance of crystal–plastic deformation features, as abrupt or progressive core-to-rim structures characterized by increasing lattice distortion and local dislocation density, associated with the development of abundant subgrains and rare newly nucleated grains. We suggest that these microstructures form while interacting with small amounts of fluids circulating along the grain boundaries. Consequently, locally the chemistry of titanite is changing. In the clinopyroxene/plagioclase-rich domains, titanite is mostly undeformed and rarely shows bending localized in discontinuous narrow rims/tips. In these domains, fluid-mediated replacement reactions are either rare or absent, as also indicated by weak chemical variations across and among grains. These observations suggest different reactivities with respect to the same P-T-fluid conditions of the two compositional domains, which coexist within the same sample at the thin section scale. U–Pb data show correlations with chemical and microstructural domains that differ as function of the composition of the microdomain. This correlation is more apparent within amphibole-rich domains where microstructures characterized by high lattice distortion/dislocations and/or subgrains show significant variations of REE, Zr, Y, Nb, U with respect to the low deformed portion of grains. These titanite domains define an isotopic population providing the youngest (Jurassic) lower intercept age. A less clear correlation between titanite chemistry and microstructures is observed in clinopyroxene/plagioclase-rich domains. Here, the rare titanites showing lattice distortion and minor Sr depletion define a population providing a similar Jurassic lower intercept age. Therefore, our results demonstrate that microstructurally and chemical calibrated U–Pb dating of titanite provides realistic ages of shear zone activity, only in case of predominance of crystal-plastic processes and of local interaction of titanite with small amounts of fluids focused along grain boundaries. Finally, the different footprints recorded by titanite grains strongly depend on the composition of cm- or mm-scale interlayered domains in which titanite occurs.

Recovery of deformation microstructure in the bulk interior revealed by synchrotron X-ray micro-diffraction

A synchrotron X-ray micro-diffraction based technique, namely differential aperture X-ray microscopy (DAXM), is used to investigate the subgrain evolution in the bulk interior during ex-situ recovery annealing of a lightly deformed Al sample. This is the first 4D DAXM study of recovery. Supplementary TEM observations reveal that DAXM enables proper reconstruction of the microstructure, with the important addition that it is in 3D. The DAXM result provides a direct observation of the 3D microstructural evolution during annealing and confirms that subgrain boundary migration is an important mechanism for subgrain growth, preferentially removing small subgrains. Moreover, it gives new evidence of subgrain coalescence as an alternative mechanism for subgrain growth—some neighboring subgrains are observed to merge due to the decrease of the misorientation angle across certain subgrain boundaries. A possible interaction of the two recovery mechanisms is discussed, as well as the advantage and limitation of the DAXM technique for recovery studies.

Nucleation of naturally occurring calcic amphibole asbestos

This article proposes an initial model of natural asbestiform minerals growing in four stages. Structures dating from the early stages of the development were observed in the damaged zone surrounding meso-fractures, more particularly in microfractures, microcavities and microcracks that lie in front of and along mesofractures. This study is limited to calcium amphiboles cross-fibers, which develop from altered calcium amphiboles. The observations were made using PLM, with some using TEM. The samples are amphibolites, dolerites and skarns from France. All these rocks have in common that they have been exposed to hydrothermal circulation which gives them a propylite character. The earliest phenomenon was the development of metasomatic veins. In these veins, actinolite form pseudomorphs after hornblendes. The new amphiboles preserve the original morphology of hornblende, in particular the appearance of the cleavages. In the second stage, hydrothermal Fluid circulation promotes the development of subgrains (DSG) with boundaries generally parallel to the cleavage. Some sub-grains become thinner and more and more individualized due to dissolution by the hydrothermal fluid. The third stage is fracturing. The irregular ends of DSGs and amphibole debris can form the substrate of asbestiform mineral nuclei. Further dissolution of DSGs can also lead to the creation of substrates. The last stage is the nucleation and growth. The nuclei have a conical shape and variable widths, from a few microns to about ten microns. The basal parts of the asbestos minerals (BPAMs) extend the DSGs along the c axis. BPAMs have variable widths and can divide during their development at the level of transverse microcracks. BPAMs when not dividing have a morphology comparable to that of whisker nanocrystals synthesized using the vapor-liquid-crystal mechanism. The shape of the fragments from BPMAs is close to that of DSGs as both have variable widths and both have lengths controlled by microcracks.

Interaction of frictional and plastic deformation mechanisms in a clay-carbonate strike-slip fault (Northern Calcareous Alps, Austria)

This study presents microstructural investigations of limestone fault rocks formed in a shallow crustal (∼4 km), compressional segment of the Salzachtal-Ennstal-Mariazell-Puchberg fault in the Northern Calcareous Alps. The investigated fault strand accommodated sinistral slip of several hundreds of meters. Our data show that fault rocks underwent various stages of evolution including the emplacement of fluidized clays at an early frictional stage of faulting overprinted by intense veining and stylolite formation. Increased calcite dissolution along clay-carbonate boundaries is resulting in the development of cleavage domains. Such clay-enriched stylolites and cleavage domains localized further deformation, producing a network of small-scale clay-rich shear zones of up to 1 mm thickness anastomosing around carbonate microlithons, varying from several mm down to some μm in size. Beside pressure-solution processes, calcite microlithons show microstructures typical for crystal-plastic deformation, including deformation twinning, undulose extinction and the development of subgrains. The investigated fault rocks are excellent examples for the interplay of frictional, pressure solution and crystal plastic deformation processes under low-temperature conditions.

Grain refinement of Al–Zn–Mg alloy during equal channel angular pressing (ECAP)

Locally produced Al–Zn–Mg alloy was subjected to severe plastic deformation through Equal Channel Angular Pressing (ECAP) technique at temperatures of 150 °C and 200 °C. Rectangular thick-walled medium carbon steel die (σc = 450Mpa, σy = 176Mpa) with an L-shaped channel of uniform configuration to provide the pressing chamber was used. Four ECAP passes were imposed consecutively on set of samples for 150 °C and 200 °C temperatures, and characterized with optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD). The phases were identified by X-ray diffraction (XRD) using monochromatic Cu Kα radiation, while vickers’ microhardness and tensile tests were performed for mechanical properties examination. Optical micrographs showed no tangible precipitation in the as cast samples with reduced grain width and deformation bands but at high temperatures of 150 °C and 200 °C, precipitation was promoted as a result of slipping systems activation. SEM images of the as-cast alloy exhibits dendrites of 250 ± 20 μm in size with η′ phase (MgZn2) precipitates in the inter-dendritic regions. For 150 °C ECAP temperature, a significant refinement was achieved as the passes increased with sub-grain development within the boundary and the precipitate observed has a grain size of 35 ± 15 μm, 25 ± 10 μm, 15 ± 8 μm and 8 ± 6 μm for first, second, third and fourth passes respectively. However, grain sizes of 85 ± 15 μm, 50 ± 10 μm, 30 ± 8 μm and 10 ± 5 μm for first, second, third and fourth passes were observed for 200 °C ECAP temperature. XRD results showed peaks for aluminum and other phases in as-cast condition with precipitates growth in the alloy after the first pass, identified as metastable η′ phase. As the number of ECAP passes increases, η′ peaks moved towards the equilibrium η phase confirming the transformation of η′ phase to stable η phase. The microhardness, Ultimate tensile strength (UTS) and the yield strength of Al–Zn–Mg alloy in different conditions of 150 °C and 200 °C respectively also increased with increase in the number of ECAP passes. This is due to increase in dislocation density, work hardening and grain refinement during ECAP process.

Uncovering the machining mechanism of polycrystalline gold nanowires by nanoskiving

The unique size effects of nanowires have inspired their implementation in superconducting materials, micro/nano electromechanical systems, and flexible devices. Nanoskiving technology has demonstrated significant potential for nanowire preparation owing to the low equipment requirements, simple operation, and wide material compatibility compared with traditional lithographic nanofabrication methods. However, the increasing application of nanowires has imposed strict requirements regarding their microstructure, morphology, and size accuracy. Limited research efforts have focused on the nanowire formation mechanism during nanoskiving, and therefore, it is difficult to prepare high-quality nanowires using this technique. The present study investigates the effects of the cutting depth on the machining (nanoskiving) mechanism of polycrystalline gold nanowire preparation. Molecular dynamics simulations indicate that the interference of grain boundaries and the extrusion of the tool lead to the formation and evolution of sub-grains. The specific energy, dislocation density, and nanowire thickness deviation all increase exponentially with decreasing depth of cut, thereby revealing a significant size effect. The nanowire microstructures, morphology, and dimensions are measured experimentally using transmission electron microscopy and atomic force microscopy, and the results are consistent with the simulations. This work provides insights into the cutting deformation mechanism during the nanoskiving of polycrystalline gold materials and contributes to the precise and controllable fabrication of nanostructures by the nanoskiving method.

Formation of nanostructured surface layer, the white layer, through solid particles impingement during slurry erosion in a martensitic medium-carbon steel

The extremely altered topmost surface layer, known as the white layer, formed in a medium-carbon low-alloy steel as result of impacts by angular 10–12 mm granite particles during the slurry erosion process is comprehensively investigated. For this purpose, the characteristics, morphology, and formation mechanism of this white layer are described based on the microstructural observations using optical, scanning and transmission electron microscopies as well as nanoindentation hardness measurements and modelling of surface deformation. The white layer exhibits a nanocrystalline structure consisting of ultrafine grains with an average size of 200 nm. It has a nanohardness level of around 10.1 GPa, considerably higher than that of untempered martensitic bulk material (5.7 GPa) achieved by an induction hardening treatment. The results showed that during the high-speed slurry erosion process, solid particle impacts brought forth conditions of high strain, high strain rate, and multi-directional strain paths. This promoted formation of a cell-type structure at first and later, after increasing the number of impacts, development of subgrains following by subgrain rotation and eventually formation of a nanocrystalline structure with ultra-high hardness. The model confirmed that high strain conditions - much higher than required for the onset of plastic deformation - can be achieved on the surface resulting in severe microstructural and property changes during the slurry erosion test.

The Research on Recrystallization Behaviors and Mechanism of a Medium-Density Ni-Based Alloy

Revealing the recrystallization behavior and mechanism of this new alloy is of great significance to subsequent research. In this study, the Ni-36.6W-15Co ternary medium heavy alloy was solution-treated at 1100–1200 °C for different lengths of time. The grain size change, microstructure and texture evolution as well as twin development during recrystallization annealing were analyzed using SEM, EBSD and TEM techniques. The study found that complete recrystallization occurs at 1150 °C/60 min. In addition, it takes a longer amount of time for complete recrystallization to occur at 1100 °C. The value of the activation energy Q1 of the studied alloys is 701 kJ/mol and the recrystallization process is relatively slow. By comparing the changes of microstructure and texture with superalloys, it is found that the recrystallization mechanism of the studied alloy is different from that of the superalloy. The development of annealing twins has a great influence on the recrystallization behavior and mechanism. The results show that the twin mechanism is considered as the dominant recrystallization mechanism of the studied alloy, although the formation and development of sub-grains appear in the early stage of recrystallization.

Grain refinement mechanism in 6082 Al alloy fabricated by cryo-multiaxial forging

In the present investigation, grain refinement mechanism in 6082 Al alloy fabricated by multi-axial forging at liquid nitrogen temperature (MCF) was proposed. The hardness and tensile properties were correlated to the microstructural characteristics of the processed alloy. The samples were subjected to open die MCF up to the 2 cycle (true strain = 1.26), 4 cycle (true strain = 2.52), and 6 cycle (true strain = 3.78), respectively. With the increased number of induced forging cycles, strength of the processed samples was significantly increased. The number density of dynamic recrystallized (DRXed) grains has significantly increased as the number of induced MCF cycles increases. The micro-texture analysis suggested the presence of the strong recrystallization (Rotated Cube ({001} <110>)) and strong deformation (Goss ({110}<001>) & Cu ({112}<111>)) texture components, after inducing the total true strain of 3.78. The supressed and broadened differential scanning calorimetry (DSC) exothermic peaks of β″&β′-phases of the MCF up to 6 cycles have revealed the high dislocation density in the processed samples. The MCF up to 6 cycles, followed by isochronal annealing treatment of Al alloy exhibit the highest strength in all investigated conditions. It was occurred due to the grain boundary strengthening owing to the development of nano-size sub-grains, as well as formation of needle shape β″-phases, which imparted the greater pinning effect during the interaction with the dislocations and grain boundaries.

Characterization of microstructure and texture of binary Mg-Ce alloy processed by equal channel angular pressing

The characterization of microstructure and texture development of binary Mg-0.3Ce (wt%) after equal-channel angular pressing (ECAP) processing via route Bc at 300 and 350 °C through 4 passes were investigated using electron backscatter diffraction (EBSD) measurements. The results demonstrated an effective grain refinement from millimeter range to 6.7 and 8.3 μm obtained after 4 passes at 300 and 350 °C, respectively. The grain refinement was obtained through dynamic recrystallization (DRX). At 300 °C, DRX occurred at low strain by twin-induced dynamic recrystallization (TDRX) and particle stimulated nucleation (PSN) mechanism and then converted with increasing strain to sub-grain development (SD) and grain boundary bulging dynamic recrystallization (GBBDRX). Besides, grain growth occurred during processing at 350 °C. The texture development strongly depends on the strain level, deformation temperature and DRX mechanisms. At 300 °C, a typical basal texture with a deviation of 40° towards extrusion direction was formed gradually up to 4 passes while a completely different texture was formed at 350 °C due to the large grain size.

Evolution of Subgrains, Dislocations, and Mechanical Properties in a 2524Al Alloy during High-Strain Rate Rolling

Evolution of Subgrains, Dislocations, and Mechanical Properties in a 2524Al Alloy during High-Strain Rate Rolling

Microstructure evolution and residual stress distribution of nanostructured Mg-8Gd-3Y alloy induced by severe shot peening

A gradient nanostructured layer was prepared on the surface of Mg-8Gd-3Y alloys by severe shot peening (SSP). The microstructure evolution, residual stress distribution and mechanical property of the gradient nanostructured layer were systematically investigated by Rietveld refinement, transmission electron microscopy, and X-ray stress and hardness analyses. The results show grain sizes of the peened samples were 80–100 nm at the top surface and increased gradually with depth. The refinement process of Mg-8Gd-3Y alloys to nano size during SSP mainly involved three steps: i) introduction of deformation twinning and dislocations in grains with a large size, ii) subdivision of large grains into substructures by twin-twin interaction and dislocation cells interacting twins, iii) evolution of subgrains to nanograins by the dislocation-assisted lattice rotation. Simultaneously, high-level compressive residual stresses were induced with a maximum magnitude of −206 MPa. Besides, the surface roughness values obviously increased and several surface cracks were detected at the near surface, which might have detrimental effects on surface behavior. Owing to the microstructural improvement, the top surface of the peened Mg-8Gd-3Y alloy attained the maximum microhardness of 155 ± 5 HV, exhibiting approximately 2 times higher than the pristine alloy.

Strain localization and fluid-assisted deformation in apatite and its influence on trace elements and U–Pb systematics

This paper presents electron backscatter diffraction (EBSD), trace element and U–Pb data of apatite grains from a granitic mylonite from the Taxaquara Shear Zone (SE Brazil). The mylonite recrystallized under upper-greenschist facies and presents two types of apatite with distinct microstructures. Type-1 apatite appears in quartz-rich layers and does not exhibit any microstructural, crystallographic, or chemical evidence of deformation/recrystallization, and resembles the original igneous apatite. Type-2 apatite appears in mica-rich layers and exhibits core-and-mantle microstructures, and intragranular subgrain development, suggesting that they have undergone dynamic recrystallization. Recrystallized tails of type-2 apatite grains exhibit a strong c-axis crystallographic preferred orientation parallel to the X-direction (stretching lineation), and lack evidence of dislocation density. This evidence from type-2 apatite grains, combined with REE depletion, high La and a negative Ce anomaly compared to type-1 grains, suggests that type-2 apatite tails underwent recrystallization via dissolution-precipitation creep, whereas parental grains underwent crystal-plastic deformation and subgrain formation through dynamic recrystallization. Phase-equilibrium modelling and quartz CPO opening-angle thermometry are consistent with recrystallization at ∼480 – 530°C and 2.2 – 5.0 kbar. We were not able to determine precise deformation ages from type-2 apatite because fluid-assisted recrystallization appears to have substantially decreased the U/Pb ratio. We find that preferential fluid flow along high-strain, biotite-rich layers in the mylonite caused type-2 apatite to recrystallise, whereas type-1 apatite in low strain layers was unaffected and retained the characteristics of the protolith.

Continuous dynamic recrystallization in a Zn–Cu–Ti sheet subjected to bilinear tensile strain

Research on zinc sheet formability, relevant for its technological applications, requires deeper understanding of the microstructural features that govern the plastic response of the material. In this work, a microstructural analysis by means of electron back-scattered diffraction (EBSD) technique was conducted on a commercial Zn–Cu–Ti sheet subjected to a bilinear tensile test at room temperature and low strain rate (5 × 10−4 s−1). The refinement of the granular structure is analyzed in terms of the development of subgrains within initially large grains, which eventually evolve into high angle boundary grains. This continuous dynamic recrystallization (CDRX) mechanism appears as a key factor in order to explain the grain fragmentation process and the weakening of the texture observed during straining of this alloy.

Dynamic microstructural evolution and recrystallization mechanism during hot deformation of intermetallic-hardened duplex lightweight steel

Dynamic microstructural evolution and recrystallization mechanism during hot deformation of intermetallic-hardened duplex Fe-9Al-10.8Mn-4.5Ni-0.7C (wt.%) lightweight steel have been comprehensively examined at various deformation temperatures at a fixed strain rate of 0.001 s−1. The flow curves are predicted employing Avrami exponent obtained from the strain dependent Johnson-Mehl-Avrami-Kolmogorov relation, which is further corroborated with the dynamic microstructural response. A detailed analysis of the intermetallic precipitates and elemental partitioning in both the ferrite and austenite phases are performed. The ferrite matrix having uniformly distributed nano-sized B2 (NiAl) precipitates has a higher micro-hardness as compared to the austenite matrix, which corroborates the strain partitioning in the austenite phase during hot deformation. Two distinct restoration mechanisms are observed in this alloy viz. continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) following hot deformation. The CDRX mechanism in the ferrite and austenite phase is characterised by the progressive misorientation development of subgrains into high-angle boundary during straining. The ferrite phase is associated with CDRX mechanism at all the deformation temperatures (1223–1423 K) albeit DDRX-like mechanism, facilitated by austenite/ferrite interphase is found to be an assisting mechanism towards the higher temperatures (1323–1423 K). The austenite phase, on the other hand, exhibits DDRX mechanism during the initial stage and dominant CDRX at the later stage of deformation at lower temperature (1223–1323 K). With the increasing deformation temperature to 1423 K, the dissolution of boundary-B2 precipitates in austenite facilitates the boundary migration, thus promoting the DDRX accompanied by the twinning in this phase.