Abstract
Austenitic stainless steel is one of the second generation advanced high strength steel which finds application in automobile, aerospace and cryogenic components. The component made of austenitic steel might operate in subzero temperature condition because of its excellent formability even at subzero temperature. In the present work several tensile tests were performed on austenitic stainless-steel sheet of thickness 1.2 mm at 0°C, -40°C, -80°C, -120°C and at different strain rates of 0.01/sec,0.001/sec,0.0001/sec. The resultant mechanical properties, like yield strength, tensile strength, elongation percent and strain hardening exponent, along with phase fractions and microstructural properties were analyzed to understand the reasons for change in mechanical properties, on comparing with room temperature properties. It was noticed that tensile strength is 635 Mpa, & strain hardening exponent is 0.38 at room temperature (25 °C) and tensile strength is 1236 Mpa, & strain hardening exponent is O.49 at -120°C. Similarly, XRD characterization revealed that strain induced martensite increased from zero percent at 25°C (room temperature) to 57 percent at-120°C Similarly EBSD characterization revealed that grain average misorientation which also increased from room temperature to-120°C.
Highlights
Stainless steels are basically alloys of Iron (Fe), carbon(C), and chromium (Cr), exhibits excellent corrosion resistance property because of the strong, non-porous chromium oxide layer (Cr2O3) on the surface of the steel
The resultant mechanical properties, like yield strength, tensile strength, elongation percent and strain hardening exponent, along with phase fractions and microstructural properties were analyzed to understand the reasons for change in mechanical properties, on comparing with room temperature properties
XRD characterization revealed that strain induced martensite increased from zero percent at 25°C to 57 percent at-120°C EBSD characterization revealed that grain average misorientation which increased from room temperature to-120°C
Summary
Stainless steels are basically alloys of Iron (Fe), carbon(C), and chromium (Cr), exhibits excellent corrosion resistance property because of the strong, non-porous chromium oxide layer (Cr2O3) on the surface of the steel. Whereas Austenitic stainless-steel show FCC structure & contains very low carbon in the range of 0.02 to 0.06% with 18% to 20% chromium along with 8% to 10% nickel. Austenitic Stainless steels are corrosion resistant and ductile than others, having excellent formability at room temperature, even at subzero temperature because of stable of Austenite phase. These steels are best preferred for cryogenic applications. Because of low stacking fault energy aprox 17MJ/.M2, Austenite phase transforms to Martensite on deformation. This strain induced martensite [5, 8,9] increases strength and hardness of the component. Etched with etchant 1:3 hydrochloric acid and nitric acid, microstructure revealed at .1000X magnification on Zeiss optical Microscope as shown in figure 6
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