• Worsnop, F. F.
• Douglas, J. O.
• Dye, D.

Abstract

<jats:title>Abstract</jats:title><jats:p>Carbon is a well known austenite stabiliser and can be used to alter the stacking fault energy and stability against martensitic transformation in medium Mn steels, producing a range of deformation mechanisms such as the Transformation Induced Plasticity (TRIP) or combined Twinning and Transformation Induced Plasticity (TWIP + TRIP) effects. However, the effect of C beyond quasi-static tensile behaviour is less well known. Therefore, two medium Mn steels with 0.2 and 0.5 wt pct C were designed to produce similar austenite fractions and stability and therefore tensile behaviour. These were processed to form lamellar and mixed equiaxed + lamellar microstructures. The low C steel had a corrected Charpy impact energy (KV<jats:inline-formula><jats:alternatives><jats:tex-math>_{10}</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>10</mml:mn></mml:msub></mml:math></jats:alternatives></jats:inline-formula>) of 320 J cm<jats:inline-formula><jats:alternatives><jats:tex-math>^{-2}</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow /><mml:mrow><mml:mo>-</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math></jats:alternatives></jats:inline-formula> compared to 66 J cm<jats:inline-formula><jats:alternatives><jats:tex-math>^{-2}</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow /><mml:mrow><mml:mo>-</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math></jats:alternatives></jats:inline-formula> in the high C steel despite both having a ductility of over 35 pct. Interface segregation, <jats:italic>e.g.</jats:italic>, of tramp elements, was investigated as a potential cause and none was found. Only a small amount of Mn rejection from partitioning was observed at the interface. The fracture surfaces were investigated and the TRIP effect was found to occur more readily in the Low C Charpy specimen. Therefore it is concluded that the use of C to promote TWIP +TRIP behaviour should be avoided in alloy design but the Charpy impact performance can be understood purely in terms of C in solution.</jats:p>

Topics

• impedance spectroscopy
• microstructure
• surface
• Carbon
• laser emission spectroscopy
• steel
• plasticity
• deformation mechanism
• ductility
• stacking fault