Abstract
The tensile properties of a metastable chromium–manganese steel are influenced by the deformation induced γ→ε→α′ martensitic transformation. While beneficial in increasing the strain hardening rate and ultimate tensile strength, the presence of substantial amounts of ε-martensite can lead to a brittle, transgranular fracture mode. An investigation has been made of the effect of prior thermomechanical processing on transformation and plastic deformation in a 10Cr–18Mn steel. Two different approaches were used: low temperature deformation and subsequent heat treatment, and high temperature deformation alone. The influence of these treatments on stress–strain behaviour and fracture is discussed. Transformation kinetics were studied by means of X-ray diffraction and magnetic measurements. Microstructural observations have shown that dislocation substructures introduced by prior deformation inhibit transformation by acting as barriers to the growth of ε-platelets. The resultant decrease in the volume fraction of martensite leads to an increase in ductility and the appearance of a region of non-uniform elongation before failure.
MST/1280
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