Surface analytical chemical imaging and morphology of Cu-Cr alloy

Cu-Cr alloys are very interesting materials to study non-equilibrium phase transformations in binary systems containing immiscible metals as well as for practical applications as high-thermal conductivity and contact materials. We studied by high resolution secondary ion mass spectrometry and atomic force microscopy the chemical element distributions and surface morphology of Cu-Cr alloys irradiated with a low energy, high current electron beam. The irradiation conditions were: energy density 4 divided by 6 J cm(-2), pulse duration 2.8 divided by 3.6 mu s, number of shots 16. Cu-Cr alloys were prepared by powder metallurgy and contain 30 wt.% Cr. While in samples irradiated at low energy density maps of surface elements reveal the presence of well separated micrometer-sized domains of Cr and Cu, after irradiation at high energy density sub-micron spots of coexisting Cu and Cr appear. This is a clear indication of CuCr compound formation, as also supported by local mass spectrometry. Irradiated samples have reduced roughness, especially in Cr domains, with respect to the pre-treated sample. However, microcracks and microcraters appear as beam energy density and number of shots increase, thus compromising the smoothening effect and the surface integrity. (c) 2005 Elsevier B.V. All rights reserved.