Processing and microhardness of bulk Cu-Fe nanocomposites

Full-density bulk nanocomposites have been developed in the immiscible Cu-Fe system through a powder metallurgy route. Elemental copper and iron powders were first mechanically alloyed to form single-phase, nanocrystalline, metastable solid solutions, Cu100-xFex (x=0 to 100). These solid solutions were subsequently decomposed into Cu/Fe two-phase domains of various volume fractions during the hot consolidation process,forming in situ nanophase Cu-Fe composites. Full-density compacts have been produced at relatively low consolidation temperatures (< 500 degrees C) by employing sinter forging at high applied pressure and a protective atmosphere. Such a consolidation scheme, coupled with enhanced grain size stability due to the unique microstructural evolution sequence involved, retained the grain sizes in the nanometer range for both Cu and Fe grains in the composite products. Fully dense composite specimens exhibit enhanced microhardness as compared with rule-of-mixtures predictions. This enhancement is attributed to interface strengthening at fcc-bcc interphase boundaries.