Composite materials and their production

A composite material comprising aluminium or an aluminium alloy reinforced with a fibre or whisker form of unmodified alumina which has been produced by a process which comprises (a) introducing into a mould containing a mat of unmodified alumina in fibre or whisker form, said mould and said mat having been preheated to a temperature in the range of 700.degree. C. to 1050.degree. C., a molten mass of aluminium or of an alloy of aluminium free from any element which reacts with said alumina in said temperature range in an amount sufficient to cover said mat with molten metal after application of pressure thereto, said aluminium or alloy being at a temperature below that at which said fibres or whiskers are attacked thereby (b) directly applying to the contents of said mould sufficient mechanically applied pressure to overcome the surface tension existing between said unmodified alumina and said molten mass and thereby ensuring that said molten mass fully penetrates the interstices of said alumina mat, said applied pressure being at least 75 kg/cm.sup.2, and (c) allowing said molten aluminium or alloy thereof to solidify in contact with said unmodified alumina mat.