Papers by Keyword: Cu Based Alloys

Abstract: The precipitation behavior of nano–scale particles formed in Cu–base alloys was studied by means of transmission electron microscopy (TEM) and SQUID measurements. Linear arrangements of two or more nano–scale particles cubic in shape were observed in the <100> orientations of matrices in a Cu–Co alloy. Although the trend was less explicit in a Cu–Fe alloy, Fe precipitates accompanying twin–like lattice modulations were found in the decomposition, when no deformation was applied. The present SQUID measurements revealed several significant influences to magnetic properties were induced during the precipitation in Cu–base alloys. Lorentz electron microscopy confirmed that phase transformation from γ → α occurred at the stage that the Fe particles reach to 40~60nm in size.

Abstract: The study of the kinetics of martensitic phase decomposition in the Cu-10wt.%Al alloy with Ag additions showed that the presence of Ag retarded the eutectoid decomposition reaction and enhanced martensite stabilization. This stabilization effect was attributed to Ag atoms redistribution as structure defects, increase in the numbers of Cu-Al pairs due to Ag-Al interaction and the Al atoms redistribution around one Cu atom at the sub-lattice of the martensitic crystal.

Abstract: This work reports on the production of Cu-Hf-Ti bulk glassy composites through a powder metallurgical route, i.e. by mechanical alloying and subsequent spark-plasma sintering. Powders of Cu60Hf30Cu10 and Cu60Hf25Ti15 composition were prepared using a high-energy planetary ball-mill. Both alloys nearly showed a fully amorphous structure with only a small fraction of residual HCP Hf grains left after 50 h of milling. Differential scanning calorimetry (DSC) analyses of the milled glassy powder revealed a two-stage crystallization process for both compositions. However, the released crystallization enthalpy was substantially larger for the Cu60Hf25Ti15 alloy than for the Cu60Hf30Ti10 alloy, suggesting that the former comprises a higher fraction of the amorphous phase than the latter. Both powders showed distinct glass-transition with a large super-cooled liquid region. Consolidation of Cu60Hf25Ti15 powder was carried out by means of spark-plasma sintering at applied pressures of 200 and 500 MPa, choosing a sintering temperature within the super-cooled liquid region (T = 753 K). The sintered compacts exhibited some pores and interparticle boundaries.