Magnetic precipitation hardening and Bloch-wall pinning in an 85Co-12Fe-3Nb alloy

Journal Article · Sat Jul 01 04:00:00 EDT 1978 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.325380· OSTI ID:6941748

Prokop, G S; Soffa, W A

The development of intrinsic coercivity during isothermal aging of a solution treated and quenched 85Co-12Fe-3Nb alloy was studied. The hysteresis loops, initial susceptibility, and magnetization were also measured and provided information for identifying the mechanism of coercivity development. Successive hysteresis loops clearly demonstrate that Bloch-wall pinning dominates the reversal mechanism in this alloy. The maximum coercivities found during isothermal aging were 21.5, 33, and 37 Oe at 800, 750, and 700 /sup 0/C, respectively. The microstructure at maximum coercivity consisted of Widmanstaetten plates of a phase similar to Co/sub 3/Nb which formed along the )111) planes of the ferromagnetic matrix. At the lowest aging temperature, 700 /sup 0/C, a metastable ordered L1/sub 2/ ..gamma..' phase formed during the early aging times resulting in a significant increase in the coercivity compared to the solution-treated samples. The periodic microstructure associated with the ..gamma..' phase also resulted in an extremely low initial susceptibility. After prolonged aging, the ..gamma..' was replaced by the Widmanstaetten precipitates. The decrease in coercivity for long aging times at 750 and 800 /sup 0/C was the result of continued coarsening of the Widmanstaetten morphology. The alloys magnetically hardened by the periodic ..gamma..' microstructure exhibited hysteresis behavior indicative of homogeneous wall pinning, whereas the alloys hardened by the Widmanstaetten precipitate showed the behavior characteristic of inhomogeneous wall pinning.

• Research Organization: Department of Metallurgical and Materials Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
• OSTI ID: 6941748
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 49:7; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
AGING
ALLOYS
BLOCH WALL
COBALT ALLOYS
COBALT BASE ALLOYS
COERCIVE FORCE
CRYSTAL STRUCTURE
DOMAIN STRUCTURE
ELECTRON MICROSCOPY
HEAT TREATMENTS
HYSTERESIS
IRON ALLOYS
MAGNETIC FLUX
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
MAGNETIZATION
MICROSCOPY
MICROSTRUCTURE
MORPHOLOGY
NIOBIUM ALLOYS
PHYSICAL PROPERTIES
PRECIPITATION
QUENCHING
SEPARATION PROCESSES