Microstructural development and its effects on tensile properties of a high Ni TRIP steel produced by repetitive corrugation and straightening via rolling (RCSR)

Microstructural development and its effect on tensile properties of a Fe- 24Ni-0.3C Transformation Induced Plasticity (TRIP) steel subjected to repetitive corrugation and straightening via rolling (RCSR) process was investigated in this study. Microstructure developed during the application of one to 45 cycles of RCSR on TRIP steel sheets were analyzed by optical microscope and scanning electron microscope (SEM) equipped with electron backscatter diffraction detector and X-ray diffraction techniques. Results indicated that the volume fraction of martensite formed due to the deformation-induced by amplification of applied strain during RCSR process was about 75% accompanied with the formation of a large fraction of low angle boundaries. To study, tensile and hardness tests were carried out on several deformed samples their mechanical properties. The results also showed that after 40 cycles of the RCSR process, yield strength increased from 150 MPa in the starting material to 1157 MPa in the deformed state. As well, the uniform elongation reduced from 170% to 30% and the hardness value increased from 130 to 340 HV. This amount of improvement in tensile strength for this type of alloy by the application of RCSR has not been reported to date. Therefor the technique used in this research for the improvement of tensile properties can be very helpful for an alloy designer when very high tensile properties for a particular application is required.