Search

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. [ABSTRACT FROM AUTHOR]

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 55 µm 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 15–40 mJ/m 2 . 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. [ABSTRACT FROM AUTHOR]

An attempt has been made to understand the kinetics concerning the manufacturing schedule of high strength 304 stainless steel comprising formation of strain-induced α′ martensite in the course of cold rolling (25%) at 0°C and its reversion during annealing in the temperature range of 300–800°C for 1 h. Increase in reversion with increasing annealing temperature without any perceptible grain growth up to 800°C has been demonstrated by the microstructural investigation. X-ray diffraction analysis has revealed that the 25% cold rolling has resulted in the formation of 20% deformation induced martensite which after annealing at 800°C has been reduced to 8%. Different stages of reversion behaviour have been envisaged by carrying out differential scanning calorimetry. Activation energies of the reactions involved during reversion have been determined by Kissinger method. Results are compared and found to be in good agreement with the published data. [ABSTRACT FROM PUBLISHER]

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 1589 MPa 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 1225 MPa 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. [ABSTRACT FROM AUTHOR]