Martensitic and austenitic phase transformations in Fe-C nanowires

BJ Wang and E Sak-Saracino and L Sandoval and HM Urbassek, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 22, 045003 (2014).

DOI: 10.1088/0965-0393/22/4/045003

Using molecular-dynamics simulation, we study the austenitic and martensitic phase transformation in Fe-C nanowires with C contents up to 1.2 at%. The transformation temperatures decrease with C content. The martensite temperature decreases with wire diameter towards the bulk value. During the transformation, the bcc and fcc phases obey the Kurdjumov-Sachs orientation relationship. For ultrathin wires (diameter D <= 2.8 nm), we observe wire buckling as well as shape-memory effects. Under axial tensile stress the martensite transformation is partially suppressed, leading to strong plastic deformation. Under the highest loads, the austenite only partially back-transforms while the crystalline phases in the wire re-orient giving the multi-phase mixture a high tensile strength.

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