The present study deals with the influence of cold rolling on microstructure, texture and mechanical properties of low carbon high Mn TWIP steel. It is noticed that the hardness, yield strength and ...tensile strength of the specimens increase whereas percentage elongation decreases as the amount of cold rolling reduction increases. The fully austenite phase with the average grain size of about 55µm along with annealing twins became fragmented and flattened when subjected to 10–50% cold deformation. The cold deformation results in the evolution of sub-structure, comprising dislocations, twins as well as interaction of dislocations and twins. The hot rolled and air cooled sample (0% cold deformation) reveals γ-fibre (〈111〉//ND) texture, whereas cold rolled samples shows Goss texture ({110}〈001〉) and Brass texture ({110}〈112〉) components, which are expected after cold deformation of austenitic steels having lower stacking fault energy in the range of 15–40mJ/m2. X-ray line profile analysis through extended convolution multiple whole profile fitting method is utilised to quantify the dislocation density and planar fault (twin) probability for the cold rolled samples with different degree of reduction. Fractography shows that with the increase in cold deformation, fractures become more and more brittle in nature.
•Microstructure and corrosion performance are compared for two structural steels.•Microstructure evolution shows primarily ferrite-pearlite in both the steels.•Steels show higher corrosion rate in 1% ...HCl solution than in 3.5% NaCl solution.•The corrosion products show the presence of oxide, hydroxide and oxy-hydroxides.•The corroded surface reveals morphologies like flowery, cotton balls and rosette.
A comparison on microstructure and corrosion performance has been made between the two structural steels used in old railway girder bridge (Sample A) and modern grades of weathering structural steel (Sample B). The microstructures, viewed under optical microscope and scanning electron microscope (SEM), show mainly ferrite-pearlite phase constituents in both the steels, A and B. The phase fraction analysis shows higher amount of pearlite in steel A compared to that of steel B. The grain size of steel A is larger than that of steel B under identical processing condition. The immersion corrosion test in 3.5% NaCl shows that the corrosion rate of steel A increases with time, while the same for steel B decreases with time. On the other hand, corrosion test in 1% HCl shows that the corrosion rate of both steel A and B is higher as compared to that of NaCl which always decreases with time. The XRD analysis of corrosion products show the presence of many oxides, hydroxide and oxy-hydroxide like Lepidocrocite (γ-FeOOH), Goethite (α-FeOOH), Akaganeite (β-FeOOH), Magnetite (Fe3O4) and Maghemite (γ-Fe2O3) in both the steels. The SEM images of corroded surfaces reveal different morphologies like flowery, cotton balls and rosette etc. which indicate that the corrosion products primarily contain Lepidocrocite (γ-FeOOH), Goethite (α-FeOOH) and Akaganeite (β-FeOOH).
A low-carbon microalloyed steel containing high Ni and Cu content has been developed and subjected to thermo-mechanical processing by varying the finish rolling temperature (FRT∼850–750°C) and ...cooling rates (air cooling and water quenching). Microstructures of air cooled samples consist of granular bainite and lath or plate-like bainite, whereas, water quenched samples exhibit a mixture of lower bainite and lath martensite. A refinement in microstructure has been noticed with the decrease in FRT and increase in cooling rate. Transmission electron microscopy demonstrates the presence of coarse (Ti, Nb)C precipitates (~90–160nm) and fine Cu precipitates (<20nm). Macro-texture and micro-texture results reveal the dominance of Goss and rotated Goss texture components, which strengthened with the decrease in FRT and increase in cooling rate. The proposed steel composition and TMCP schedule have offered YS ∼ 1000MPa, UTS ∼ 1400MPa, total elongation greater than 10% maintaining a low YS: UTS ratio (0.68–0.80). Such a satisfactory combination of tensile properties achieved in as-cooled or as-quenched conditions (without the need of any tempering treatment) makes the steel suitable for automotive application.
The present study aims to examine the deformation and annealing behaviour of Fe–0.07C–20Mn–2.6Si–1.6Al TWIP steel in the viewpoint of microstructural characterisation, fault analysis, triaxial ...residual stress measurement and mechanism of twin formation. 50% cold deformation results in improvement of hardness and tensile strength (428 HV and 1419 MPa, respectively), whereas annealing at 900 °C of the same leads to improvement in ductility (61%) with the decrease in strength (873 MPa). The residual stress is maximum and compressive in nature in deformed sample which has been diminishing after annealing. Hot rolled and hot rolled-solution treated samples develop dual phase microstructure along with annealing twins, whereas fine nano twins and high dislocation density with dual phase microstructure are apparent after 50% cold deformation. The presence of Shockley partial dislocation, overlapping of stacking faults, Lomer-Cottrell lock, intrinsic and extrinsic stacking faults affect the mechanical properties as obstacles of dislocation movements or assisting twin formation. Goss and Brass components of texture are dominating after rolling, whereas annealing results in weakening of rolling texture components. The nucleation mechanism of twin has been consistent with the pole mechanism along with the deviation process. Hence the present work amplifies the present understanding of deformation and annealing behaviour on low carbon dual phase TWIP steel from different characterisation perspectives.
The present study aims to investigate the evolution of microstructure of 304 austenitic stainless steel (SS) due to reversion annealing of cold deformed samples under different schedules. Evolution ...of phases in selected samples was identified and quantified by X-ray diffraction analysis along with corresponding microstructural characterisation through optical, scanning and transmission electron microscopy. Mechanical properties of the samples were determined by carrying out tensile test. Electron microscopy of selected samples has revealed that, while strain induced martensite, deformation twins, ε-martensite and high dislocated structures are the dominant microstructural features of the cold deformed samples, reversion annealing of the same results into ultrafine-grained reverted austenite, cell type dislocation sub-structures with some amount of untransformed martensite. The maximum tensile strength of 1589MPa with an elongation of 9% has been obtained after 20% deformation at −196°C (20LND), whereas 40% deformation at 0°C (40ZCD) results into a tensile strength of 1225MPa with 13% elongation. Annealing of 40ZCD and 20LND specimens at 300°C results in significant improvement in tensile strength, while annealing at 725°C increases the elongation with a decrease in tensile strength. During reversion annealing, strain induced martensite transforms to austenite through shear and diffusional processes. However, the reversion is essentially diffusional in nature at a higher temperature.
The present study investigates the effect of annealing time and temperature on the microstructural restoration (by recovery and recrystallization), texture evolution and tensile properties of a ...dual-phase TWIP steel. The samples, which were initially hot rolled-air cooled followed by being in solution treated condition, subsequent 50 pct cold rolled condition and different annealing conditions (temperatures ranging from 500 °C to 1000 °C for 5 minutes to 2 hours), were subjected to microstructural characterization using optical and transmission electron microscopy, electron backscatter diffraction analysis, tensile testing and fractographic study. The deformation-induced ferrite (DIF) transformation due to cold deformation, the evolution of the grain structure and texture in both austenite and ferrite, and the change in the DIF fraction (accompanying the recrystallization annealing treatment) are critically analyzed. The optimum combination of strength and ductility is achieved in the partially recrystallized samples annealed at 700 °C for 30 minutes (UTS: 859 MPa, total elongation: 37 pct) and 900 °C for 30 minutes (UTS: 708 MPa, total elongation: 63 pct).The effects of DIF on the evolution of microstructure and texture during annealing and the final properties are discussed.
Surface hardening of low carbon hot rolled C–Mn steel has been successfully performed by high power diode laser with an achievable case depth of about 300μm. The laser treated samples have been ...characterised using optical microscope, scanning electron microscope, transmission electron microscope, and X-ray diffraction techniques. Higher hardness level is achieved in laser surface hardened zone (≈300HV) than in the base alloy region (≈140HV). The variation in hardness as a function of distance across the laser tracks is observed during multi-track laser hardening. Laser hardened steel sheets show enhanced mechanical strength (YS: 383–443MPa, UTS: 476–506MPa) with the lowering of percentage total elongation (23–28%) compared to the base alloy (YS: 351MPa, UTS: 450MPa and total elongation is 32%). Strain hardening exponent (‘n’) has been evaluated from true tensile stress–strain diagram and it shows a similar nature for both base alloy and laser treated steels. The microstructure in the base alloy region consists of a mixture of ferrite and pearlite, whereas predominantly lath martensite is present in the laser hardened surface layer. The improvement of mechanical strength is discussed in terms of the formation of this hardened layer on the surface.
304 austenitic stainless steel plates have been deformed (10 to 40%) by multi-pass cold rolling incorporating soaking at 0°C and −196°C after each pass with an aim to correlate the microstructure and ...mechanical properties under cold/cryogenically deformed conditions. Characterisation of phase constituents, microstructure and mechanical properties of such steel specimens has been conducted after processing under different schedules. Rolling of the investigated steel at near cryogenic temperature results into the formation of extended stacking faults, ε-martensite and α′-martensite in contrast to the formation of homogeneous dislocation structure along with α′-martensite in the samples rolled at 0°C, which can be correlated with temperature dependent stacking fault energy. EBSD phase analysis reveals 46.3% and 69.2% α′-martensite in the austenitic matrix for 10% and 20% deformation at −196°C, respectively. Deformation twins are evident in all the samples rolled at 0°C as well as −196°C. 40% cold deformation at 0°C leads to high strength (1225MPa) and 13% total elongation, whereas comparatively lower 10–20% deformation at −196°C leads to higher level of strength (1306–1589MPa) with 15–9% elongation due to the formation of the higher volume fraction of strain induced martensite (ε/α′).
•Austenitic stainless steel has been rolled at zero and cryogenic temperatures.•Microstructure reveals presence of martensite (ε/α′), stacking faults and twins.•Deformed microstructures are attributed to low stacking fault energy.•Cryogenically deformed samples indicate maximum tensile strength.
Key message
An efficient, high-frequency, and robust in vitro regeneration protocol was developed using cotyledon and hypocotyl explants from mulberry (
Morus indica
cv. G4) seedlings.
Mulberry (
...Morus
) is a perennial tree species with a wide range of commercial applications. Its leaves are predominantly used for feeding the monophagous silkworm (
Bombyx mori
L.) globally. In this study, the effects of plant growth regulators, additives and elevated levels of macronutrients, on in vitro adventitious shoot induction, shoot elongation, and rooting, were investigated. It was found that modified Murashige and Skoog (MS) medium supplemented with thidiazuron (0.5 mg/L) provided the most suitable medium for adventitious shoot bud induction, with a regeneration frequency of 88.62%, and yielded adventitious shoot buds of 10.60 ± 0.30 per cotyledon explant. Additionally, the MS medium fortified with 6-benzylaminopurine (1.0 mg/L), gibberellic acid (1.5 mg/L)
,
silver nitrate (2 mg/L), putrescine dihydrochloride (1 mg/L), activated charcoal (AC, 0.2%), and supplementary dosage of calcium chloride (515 mg/L) resulted in the highest frequency of shoot elongation, spontaneous root induction, and the longest shoot length. In this medium, no hyperhydricity of regenerated shoots/leaves was observed. We observed the longest adventitious root length and secondary root length of the shoots grown on MS medium supplemented with indole-3-butyric acid (2 mg/L) and AC (0.2%). The frequencies of
ex vitro
survival of plantlets after hardening were 90–95% and 95–100%, under laboratory and field-like conditions, respectively. Even though in vitro regeneration protocol in mulberry is genotype-dependent and explant-specific, the robust regeneration protocol developed in this study could find its applications in genome editing and genetic transformation using cotyledon and hypocotyl explants of other cultivars.
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