GB1102339A - Dispersion-modified metals - Google Patents

Abstract

A powder metallurgy product having a density of at least 99.5% of theoretical and substantially uniform metal grain size comprises 1) a matrix metal (Fe, Co or Ni or an alloy thereof with one or more of Cr, Mo or W in an amount of up to 30% each with not more than 30% in total of Mo and W), 2) a dispersed phase consisting of 0.01-5 volume % of a refractory metal oxide uniformly dispersed in the matrix metal and having an average particle size of 5-250 millimicrons and 3) 0.005-0.3 atomic % of Mf, Zr or Mg uniformly distributed throughout the matrix, the free energy of formation of the refractory oxide being at least as great as that of any oxide of the matrix and addition metals. The refractory oxides are present in the metal grains as well as at the grain boundaries and there is no more than 2% of metal oxides other than the refractory oxide in the final product. Suitable refractory oxides are those of Zr, Al, Ce, Mf, U, Mg, Th, Be, La, Ca and Y. The product may be made by mixing a powder A) of the dispersion hardened matrix metal or alloy with B) powdered Zr, Hf or Mg, their master alloys with the matrix metal or hydrides of one of these, heating the mixture in a non-reactive environment to 0.5 to 0.9 of the absolute melting point of the powder mixture A) and consolidating the product to at least 99.5% of the theoretical in a non-reactive environment. The powder A) may be prepared by ball milling the components for an extended period of time or by the precipitation method disclosed in Specification 938,546 and the consolidation may be carried out by forging, rolling, swaging or extrusion.