Alnico is produced by casting or sintering processes. Anisotropic alnico magnets are oriented by heating above a critical temperature, and cooling in the presence of a magnetic field. Both isotropic and anisotropic Alnico require proper heat treatment to get its magnetic properties - without it its coercion is about 10 Oe - comparable to technical iron, which is a soft magnetic material. After the heat treatment alnico becomes kind of composite material, named "precipitation material" - it consist of iron and cobalt rich precipitates in rich-NiAl matrix. Alnico anisotropy is oriented if it is in external magnetic field during the precipitate particle nucleation, which occur when cooling from 900 to 800 C, near Curie point. Without external field there are local anisotropies of different orientations, due to spontaneous magnetization. The precipitate structure is a "barrier" against magnetization changes, as it prefers few magnetization states requiring high energy to get the material into any intermediate state. Also, small magnetic field change magnetization of matrix phase only, and it is reversible.
Alnico alloys have some of the highest Curie points of any magnetic material, around 800 °C, although the maximum working temperature is normally limited to around 538 °C. This property, as well as its brittleness and high melting point, is the result of the strong tendency toward order due to intermetallic bonding between aluminium and its other constituents. They are also one of the most stable magnets if they are handled properly.
As of 2008, Alnico magnets cost about $20 per lb, $4.30 per BHmax. magnetic characteristics.
Jensen Jet Blackbird Alnico speaker: CE Distribution.(NEW PRODUCTS: THE LATEST AND GREATEST IN NEW PRODUCT INTRODUCTIONS)
Mar 01, 2007; CE DISTRIBUTION HAS unveiled the new Jensen Jet "Blackbird." The Jensen Blackbird, with its 100 watts of pure alnico tone,...