GB946337A - Improvements in or relating to composite metallic bodies - Google Patents

Abstract

A sintered copper body containing a uniformly dispersed refractory oxide phase in such an amount that the sintered copper has a high electrical conductivity which is at least 90% of the international standard conductivity for pure copper, is joined to a substrate such as steel or nickel or cobalt based alloys which have a higher mechanical strength than pure copper to form a composite body such as a commutator segment. The refractory oxides may be Al2O3, MgO, BeO, or ThO2, and the sintered copper body incorporating the refractory oxide may be prepared by any of the methods disclosed in Specifications 893,425, 917,005, 919,051 and 932,460. The substrate is formed by powder metallurgy methods or by casting and the two members are united by brazing or hot rolling. In an example copper powder is mixed with an aqueous solution of magnesium nitrate, the water is evaporated and the mixture is heated in air to form a mixture of copper oxide and magnesium oxide which is crushed and heated to 300 DEG C. in hydrogen. The resulting copper-magnesium oxide mixture is compacted and sintered at 1050 DEG C. in hydrogen to give a compact containing 0.86% magnesium oxide which is hot rolled at 800 DEG C. After brazing the composite may be heat treated at 850 DEG C., quenched in oil or water and tempered at 600 DEG C.