Portland State University. Department of Physics
Date of Award
Master of Science (M.S.) in Physics
1 online resource (ix, 45 leaves, ill. 28 cm.)
Alnico 6, Iron-cobalt-nickel-aluminum-copper-titanium alloys
The purpose of this research project was to study the αᵧ phase in Alnico 6. Other phases were studies for comparison. Also the effect of an applied magnetic field on the formation of the αᵧ phase was investigated.
Three single crystals of Alnico 6 were heat treated for one hour—one at 1250°C, one at 1000°C, and one at 800°C—and water-quenched. The microstructure of each sample was observed with the optical microscope, and X-ray diffraction patterns were taken to determine the crystal structure of the phases present.
Several single crystal samples of Alnico 6 were heat treated at 1000°C and furnace-cooled. Some of the samples were heat treated and furnace-cooled in the presence of an applied magnetic field of about 5000Oe, and the others were heat treated and furnace-cooled without an applied magnetic field. Each set of samples were electrothinned, and the microstructure of the αᵧ and α₁ ₊ α₂ phases was studied using the electron microscope. Electron diffraction patterns and electron micrographs were taken from αᵧ regions and α₁ ₊ α₂ regions of each sample.
By a combination of X-ray and electron diffraction, it was determined that the crystal structure of the α, α₁, α₂ and αᵧ phases is body-centered cubic, with a lattice parameter of 2.87 Å. Electron diffraction showed that the crystal structure of the combined α₁ ₊ α₂ phases is ordered body-centered cubic, and that the lattices of these two phases are coherent. Other investigators have found that only the α₁ phase is ordered in Alnico 5 and Alnico 8 and thus is believed be the case in Alnico 6 also. Electron diffraction showed the αᵧ phase to be ordered, with the degree of ordering less than that in the α₁ phase.
Some difference was noted between the αᵧ phase formed with a magnetic field and that formed without a magnetic field. The αᵧ formed with a magnetic field showed twinning and some small lattice rotations, while stat formed without a field did not. The reason for this is not known.
Samuel, Cortez, "Investigation of the alpha-sub-gamma phase in alnico 6" (1970). Dissertations and Theses. Paper 1473.