Accession Number:

ADA564143

Title:

Effect of Nickel Content on the Crystallization Behavior in Nanocrystalline (CO1-XNIX)88ZR7B4CU1 Soft Magnetic Alloys

Descriptive Note:

Master's thesis

Corporate Author:

ALABAMA UNIV TUSCALOOSA DEPT OF METALLURGICAL AND MATERIALS ENGINEERING

Personal Author(s):

• Hornbuckle, Billy C.
• Thompson, Gregory B.
• Chopra, Nitin
• Mankey, Gary

Report Date:

2012-01-01

Pagination or Media Count:

61.0

Abstract:

A series of Co1-xNix88Zr7B4Cu1 soft magnetic alloys, where X was varied from 0 to 1, were fabricated by a melt spinning process into thin ribbons of the material. This process was followed by an isothermal anneal to produce a nanocomposite alloy, i.e. nanocrystalline grains in a residual amorphous matrix. The alloy series was designed to investigate crystallization kinetics and limits to the compositional regime where a nanocomposite could be formed. The primary and secondary crystallization temperatures of each alloy were determined using Differential Scanning Calorimetry DSC from which the crystallization activation energies were calculated using the Kissinger Method. When X exceeded 0.75, the as-spun ribbons exhibited partial crystallization, resulting in reduced exothermic crystallization peaks. For lower Ni contents, the ribbons were amorphous in the as-spun state. The activation energy for crystallization decreased with increasing Ni content. Transmission Electron Microscopy TEM and Atom Probe Tomography APT revealed fine nanocrystallite and boron segregation to the grain boundaries with increasing Ni content. The previously suspected use of Cu clustering, which can act as heterogeneous nucleation sites, showed no clear correlation with observed spatial location of the crystallites. Chemical partitioning between species in the as-spun and primary crystallization heat treatments were correlated to the resulting changes in magnetic properties. As Ni content increased, the saturation magnetization and normalized magnetization for these samples decreased accordingly.

Descriptors:

• *CRYSTALLIZATION
• *MAGNETIC ALLOYS
• *NICKEL
• ACTIVATION ENERGY
• ALLOYS
• AMORPHOUS MATERIALS
• COMPOSITION(PROPERTY)
• DIFFERENTIAL SCANNING CALORIMETRY
• ELECTRON MICROSCOPY
• EXOTHERMIC REACTIONS
• GRAIN BOUNDARIES
• HEAT TREATMENT
• HETEROGENEITY
• MELTS
• NUCLEATION
• RESIDUALS
• SATURATION
• SPINNING(INDUSTRIAL PROCESSES)
• THESES
• TOMOGRAPHY

Subject Categories:

• Properties of Metals and Alloys
• Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE