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 ÷ 6 J cm− 2, pulse duration 2.8 ÷ 3.6 μs, 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.