Microstructure and strength of CuFe in Situ composites after very high drawing strains

Modeling the electrical resistivity of deformation processed metal–metal composites

Effect of Ag on the microstructure and properties of Cu-Fe in situ composites

Copper-iron in situ composites have been produced from prealloyed, extruded powders. The extruded rods were subsequently cold drawn to various stains when the iron particles are drawn into fine fibres. The dependence of the tensile stress and the ductility on cold work has been analysed and the different microstructures have been examined to quantify their evolution with cold work. The fine scale of the initial microstructure makes it possible to obtain a high tensile stress after a relatively small reduction in area during working. The strength of such composites has previously been explained by models based on the rule of mixtures and these models are modified here to take into account the nanometre scale of the iron ribbons. Analysing the mechanical properties, it appears that the very fine scale of the ribbon-shaped iron particles makes them very strong such that they deform elastically up to very high stresses, even when the composite begins to deform in a non-elastic manner. The strength of the fine ribbons after very large drawing strain is considered to reach the theoretical limit, as the ribbons are reduced to thicknesses of about 3 nm, and beyond such strains the composite strength will probably increase at a slower rate or may saturate.

Microstructure and strength of CuFe in situ composites obtained from prealloyed CuFe powders

Powder metallurgical techniques have been employed to prepare the precursor billets in the preparation of Cu-15 vol pct Fe alloys by deformation processing. It has been demonstrated that by (1) using high-purity gas-atomized Cu powders blended with commercial high-purity Fe powders and (2) controlling the time/temperature processing conditions within specific limits, it is possible to produce Cu-Fe deformation-processed alloys with strength/conductivity properties matching those of Cu-Nb, Cu-Ta, and Cu-Cr alloys. These properties are significantly superior to the best commercial alloys.

Strength and electrical conductivity of deformation-processed Cu-15 Vol Pct Fe alloys produced by powder metallurgy techniques

Alloys of Cu-Fe with iron contents from 10 to 30 wt % have been prepared by casting plus mechanical reduction. A series of heat treatments was done at various stages of the mechanical reduction to promote precipitation of the iron from the copper matrix with the hope of optimizing electrical conductivity at a given strength level. A curve of optimum tensile strength against electrical conductivity was determined. It was found to lie significantly below the available data for Cu-Nb alloys and it is suggested that further improvements may be possible in Cu-Fe alloys by improved thermal mechanism processing.

S. C. Chueh

Papers

Strength and conductivity ofin situ Cu-Fe alloys