HOMOGENEOUS MARTENSITIC NUCLEATION IN FE-CO PRECIPITATES FORMED IN A CU MATRIX
HOMOGENEOUS MARTENSITIC NUCLEATION IN FE-CO PRECIPITATES FORMED IN A CU MATRIX
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DOI：
10.1016/0956-7151(93)90356-w
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发表时间：
1993-01-01
期刊：
影响因子：
--
通讯作者：
COHEN, M
中科院分区：
文献类型：
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作者：
LIN, M;OLSON, GB;COHEN, M
在无缺陷纳米晶 f.c.c. 中监测了低温冷却时的马氏体转变。在 Cu 基体中共格沉淀的 Fe-Co 颗粒；选择这种 Cu-Fe-Co 系统进行研究是因为 f.c.c. --> 公元前Fe-Co合金的相变驱动力异常大。研究发现，相变在大约 10 kJ/mol 的驱动力下发生，比已知的大块合金异质成核临界驱动力高 7 倍。观察到的转变特征与经典的均相相干成核完全一致，而在这种情况下可以排除异相成核和均相半相干成核。观察到的转变温度的变化可以通过实验确定的 Fe-Co 沉淀物中 Co 含量（以及因此转变驱动力）的差异与其粒径分布的关系来解释。通过施加高磁场在低温下施加驱动力的增量来证明热激活在均匀成核过程中的作用。
The martensitic transformation on subambient cooling has been monitored in defect-free nanocrystalline f.c.c. Fe-Co particles that have been coherently precipitated in a Cu matrix; such a Cu-Fe-Co system was chosen for study because the f.c.c. --> b.c.c. transformational driving force in Fe-Co alloys is exceptionally large. Transformation is found to occur at a driving force of approximately 10 kJ/mol, a factor of 7 higher than the known critical driving forces for heterogeneous nucleation in bulk alloys. The observed transformation characteristics are entirely consistent with classical homogeneous coherent nucleation, whereas heterogeneous nucleation and homogeneous semicoherent nucleation can be ruled out in this case. An observed variation in transformation temperatures is explained by the experimentally-determined differences in Co content (and, hence, in transformational driving force) among the Fe-Co precipitates in relation to their distribution of particle sizes. The role of thermal activation in the homogeneous nucleation process is demonstrated by applying a high magnetic field to impose an increment of driving force at low temperatures.