Cu Rich Nanostructured Alloys with Enhanced Mechanical Properties
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Cu Rich Nanostructured Alloys with Enhanced Mechanical Properties K. G. Georgarakis1, K. Ota1, A. LeMoulec1, F. Charlot1, A. R. Yavari1, and G. Vaughan2 1 Euronano, SIMAP-CNRS, Institut National Polytechnique de Grenoble, 1130 rue de la Piscine, St Martin d’Heres, 38402, France 2 European Synchrotron Radiation Facilities, Grenoble, 38042, France ABSTRACT New copper rich alloys with elemental additions of transition metals and group IIIA and IVA elements have been prepared by casting and rapid solidification. The prepared alloys show very interesting microstructures; a thick surface layer with nanocrystalline eutectic like structure, while in the bulk the microstructure is coarser lamellar or dendritic. Their microhardness was found to be exceptionally high for Cu rich alloys, reaching values of 450-550HV. Furthermore, the microhardness of the surface layer is higher than that in the bulk, indicating that these alloys can be considered for a variety of applications including tribological and structural. INTRODUCTION Mechanical properties of nanocrystalline copper and copper alloys have attracted considerable scientific attention for over a decade. The most common techniques used to prepare such materials are the consolidation method [1-3], cold rolling [4-6] and electrodeposition [3, 7]; the mechanical strength reported varies in a wide range of 400 MPa and 1200 MPa. In the recent past, copper-beryllium alloys have held the record for mechanical strength (1.2-1.4 GPa) [8]. High mechanical strengths of the order of 2.2 GPa were achieved in Cu-Nb nanostructured composite wires obtained by cold drawing to 99.999% reduction of cross-sectional area [9, 10]. In addition, intensive research efforts and numerous technological applications focus on materials with enhanced surface properties such as wear and scratch resistance, hardness and corrosion resistance. This is most often achieved with coatings and surface treatments [11]. In the present study, Cu based alloys with enhanced surface properties were produced by casting and rapid solidification. Several elements such as Hf, Zr, Si, Al, Ti, Ni, Cr, were used as additives. The resulting microstructure and microhardness profile indicate that we succeeded in producing alloys with enhanced surface properties without any further surface treatment.
EXPERIMENT Copper based alloys were prepared in an arc furnace under argon inert atmosphere and homogenized in cold copper crucibles using induction melting. Then, injection and suction casting techniques were applied in order to cast the alloys into copper molds with cavities of different shapes leading to the production of rods, plates, bars and discs. The melt spinning technique was also used for the production of ribbons. A high-resolution scanning electron microscope (HR-SEM) equipped with field emission gun (FEG) was employed for the microstrucural characterization of the cast alloys. The crystal structure was studied by X-ray diffraction in transmission mode using a high-energy (90 keV) high intensity monochrom
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