Method of making a two-phase or multi-phase metallic material

Abstract

A two-phase material comprises a higher-melting phase dispersed in a lower-melting matrix. The material made by the method is new since, although it consists of particles of a higher-melting-point phase (e.g. iron) dispersed in a lower-melting-point matrix (e.g. aluminium), the particles being of a material soluble in the matrix at the melting-point of the matrix, no perceptible dissolution of the particles is evident in the material. Such materials may find application as friction materials, for example, in brake pads, stair edging, decking and industrial flooring. The method comprises forming a spray of molten matrix material, introducing the particles into the spray, and directing the spray onto a colder surface to solidify the matrix spray and form the multi-phase material; the method is particularly characterized in that the temperature of the spray is below the melting point of the particles, with the result that, despite the notional solubility of the particles material, no perceptible dissolution of the particles occurs. Rapid solidification is helpful in assisting to achieve this result. Thus, the particles are in contact with molten material for a duration of preferably not more than 100 ms. To ensure this, the cooling rate of the matrix in the region of the solidus is preferably at least 10.sup.3 K/s, more preferably at least 10.sup.4 K/s.