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|To investigate the Microstructural Changes during Tensile Deformation of AISI 304L Austenitic Stainless Steels using In-Situ and Ex-Situ Tensile Experiment
Das, Swapan Kumar
|Ausnetic Stainless Steels;In-situ
|In the present times the main emphasis of research field is on improving the mechanical properties of various materials for industrial and other purposes. Austenitic stainless steels are very important materials for several applications where corrosion resistance is an important issue. The other important properties of this category of steels are very good formability, room-temperature and cryogenic toughness, good oxidation resistance and creep properties at elevated temperatures. But these steels have moderate yield strengths. Many processing routes have been developed till date to improve the mechanical strength of these steels at the expense of ductility. The main emphasis of the present work is to study and understand the microstructural changes in AISI 304L austenitic stainless steels during tensile deformation which can be used to further enhance their properties. The microstructural evaluation has been studied in respect of change in grain orientation, phase transformation and slip activated in the material during in-situ and ex-situ tensile experiments. Deformation behaviour of these steels is dependent on the crystal/grain orientation. So the microstructural changes in respect of grain orientation change and the effect of the annealing twins on the orientation change during in-situ tensile deformation at different strain levels is studied. The phenomenon of plastic deformation activated during in-situ tensile deformation and its correlation with grain orientation has also been described in the medium range of strain. In the latter part of the work, the nucleation sites of martensitic transformation from austenitic phase and its growth with increased stress has also been described in detail in bi-modal type austenite grains. It was noticed that the strain induced martensitic transformation observed in the bi-modal type austenite grains during tensile deformation is due to localized stresses induced in the small grains and in the strained grain boundary regions with high angle of misorientation.
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