Abstract
Changes in line broadening, intensity of super-lattice line, extinction effect and lattice parameter during heat treatments of an Alnico-5 magnet alloy have been observed by a counter-diffractometer. It has been shown that the highest coercive force can be attained by the smallest mean crystallite size (140∼150 Å) after the optimum aging treatment at 580°C. The values of I100⁄I200 were observed to be 0.11 after magnetic field cooling, 0.08 after aging at 580°C, 0.13 after solution-heat-treatment at 720°C and 0.09 after re-aging at 580°C. Aging at 580°C gives the highest value of I110⁄I220. The largest broadening of the (200) line after 580°C-aging suggests the presence of the tetragonality or the coherent transition state of the lattice. It has been argued that the reversible migration of the interphase boundary and the irreversible change in tetragonality are two main processes which occur during the solution-treatment and the re-aging treatment of the alloy.
