کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1446680 | 988620 | 2012 | 8 صفحه PDF | دانلود رایگان |
Molecular dynamics simulations have been used to obtain the mobility, in pure Fe, of a face-centered cubic (fcc)–body-centered cubic (bcc) interphase boundary with an orientation given by (1 1 0)bcc//(7 7 6)fcc and [0 0 1]bcc//[−1 1 0]fcc. The interface is best described by a 4.04° rotation, about an axis lying in the boundary plane, from the Nishiyama–Wasserman orientation and the boundary consists of a parallel array of steps (disconnections). An embedded atom method interatomic potential was employed to model Fe, and the free energy difference as a function of temperature between the fcc and bcc phases, which provided the driving force for boundary motion, was determined by a thermodynamic integration procedure. Although the boundary was found to be very mobile, the transformation did not proceed by a martensite mechanism. The boundary mobility was obtained for several temperatures in the range 600–1400 K and Arrhenius behavior was found with an activation energy of 16.5 ± 2.7 kJ mol−1 and a pre-exponential factor equal to 7.8( ± 0.9) × 10−3 mmol J−1 s−1. The activation energy is much lower than that extracted from experiments on the massive transformation in Fe alloys and possible reasons for the discrepancy are discussed.
Journal: Acta Materialia - Volume 60, Issue 10, June 2012, Pages 4328–4335