Homogeneous martensitic nucleation in Fe-Co precipitates formed in a Cu matrix
- Bethlehem Steel Corp., PA (United States)
- Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering
- Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering
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. [r arrow] b.c.c. transformational driving force in Fe-Co alloys is exceptionally large. Transformation is found to occur at a driving force of [approximately]10kJ/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.
- OSTI ID:
- 6471516
- Journal Information:
- Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 41:1; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
Similar Records
Kinetics of f. c. c. [r arrow] b. c. c. heterogeneous martensitic nucleation; 1: The critical driving force for athermal nucleation
Is homogeneous nucleation of martensitic transformation in iron-base alloys possible?
Related Subjects
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOY SYSTEMS
ALLOYS
BCC LATTICES
COBALT ALLOYS
COPPER ALLOYS
COPPER BASE ALLOYS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
DATA
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
FCC LATTICES
INFORMATION
IRON ALLOYS
MAGNETIC FIELDS
MICROSCOPY
NUCLEATION
NUMERICAL DATA
PHASE TRANSFORMATIONS
TERNARY ALLOY SYSTEMS