Nonlinear elastic behavior of iron-carbon alloys at the nanoscale.

Graphical abstract Highlights • Body-centered-orthorhombic martensite (bco) is stable under compressive stress. • Supersaturated ferrite exhibits a superelastic behavior near the critical point. • Martensite softens under compression and tension, and presents a Bauschinger-like effect. • Mechanical instability and variant texturing will occur in martensitic microstructures. Abstract We studied the elastic response of body-centered iron-carbon crystals. By coupling a mean-field elastochemical model with a kinetic Monte Carlo algorithm, we computed stress – composition and stress – temperature state diagrams and simulated uniaxial tensile-compressive tests on oriented variants. We found that, in addition to the well-known ferrite and bct-martensite phases, the phase diagram comprises the body-centered-orthorhombic martensite (bco), which is stable under compressive stress. The elastic response of supersaturated ferrite appears highly non-linear and exhibits a superelastic behavior near the critical point of the phase diagram. When submitted to a strain cycle, martensite softens under both compression and tension, in association with a lattice-scale Bauschinger effect. Our results suggest the occurrence of mechanical instability and resulting variant texturing in polycrystalline martensitic structures. [ABSTRACT FROM AUTHOR]