Change in deformation mechanism to change TRIP to TWIP strengthening in the class of 304 austenitic stainless steel sheets by trapezoidal wavy-rolling process

ABSTRACT

Strengthening of steels through twinning-induced plasticity (TWIP) has several advantages like high-strength and high-ductility combination over the transformation-induced plasticity (TRIP) mechanism which gives high strength, low ductility and product phase of martensite in the single phase solid solution of austenitic matrix. But, development of TWIP effect will be more difficult unless the steel contains high stacking fault energy (SFE) (>20mJ/M²), fine grain structure and high manganese alloying (15–30 wt.%). These are very expensive processes and susceptible to metallurgical complexity in the austenitic stainless steels. Therefore, new processing technology was developed for strengthening of the austenitic stainless steel sheets by trapezoidal wavy rolling (TWR). Type 304 austenitic stainless steel was selected for this study which is known as martensite transformation, a dominant hardening mechanism due to low SFE and coarse grained structure. Wavy deformation-induced results have been studied through strain hardening behaviour by flow stress-strain curves and microstructural changes by atomic force microscope (AFM), and phase transformations by using X-ray diffractometer (XRD) analysis. It is found that this process introduced changes from TRIP to TWIP mechanism by forming plenty of mechanical twins and shear bands type structure at initial stage of deformations and partial martensite is observed in advanced stage.

KEYWORDS:

• Stainless steels
• trapezoidal wavy rolling
• strain-hardening
• microstructures
• tensile properties

Acknowledgements

The author would like to express hearty thanks to the Ph.D supervisors Prof. B. P. Kashyap (Metallurgical Engineering and Material Science department, Indian Institute of Technology Bombay) and Prof. S. Sangal (Materials Science and Engineering, Indian Institute of Technology Kanpur) for their kind support and wishes in the author’s growth.

Disclosure statement

No potential conflict of interest was reported by the author(s).