Non-isothermal Characterization of the Precipitation Hardening of a Cu-11Ni-19Zn-1Sn Alloy
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INTRODUCTION
THE industry is requiring materials microstructurally stable with a high electrical and/or thermal conductivity and a large corrosion resistance for manufacturing a large number of devices such as welding electrodes, high-performance switches, rocket nozzles, etc. Copper is the most promising material for these applications because of its high thermal and electrical conductivity, although a considerable improvement of both mechanical properties and the corrosion resistance would be required for accomplishing the above requirements.[1,2] It has been shown in the literature[3–5] that Cu-Ni-Zn alloys with zinc weight percentages lower than 35 pct, which form homogeneous solid solution with a-Cu structure, are very good candidates for achieving the above purposes because of their high wear and corrosion resistance. On the other hand, Zhou et al.[6,7] have recently reported that the addition of a small percentage of aluminum dramatically improves the mechanical properties of the annealed alloy because the addition of this metal promotes the formation of nanosized precipitates of an ordered Cu2NiZn phase. It is noteworthy to point out that the precipitation hardening
E. DONOSO and R. ESPINOZA are with the Departamento de Ciencia de los Materiales, Facultad de Ciencias Fı´ sicas y Matema´ticas, Universidad de Chile, Avda. Tupper 2069, Beauchef 851, 8370456 Santiago, Chile. M.J. DIA´NEZ and J.M. CRIADO are with the Instituto de Ciencia de Materiales de Sevilla, Centro Mixto Universidad de Sevilla-C.S.I.C., Ame´rico Vespucio 49, 41092 Sevilla, Spain. Contact e-mail: [email protected] E.MOSQUERA is with Departamento de Ciencia de los Materiales, Facultad de Ciencias Fı´ sicas y Matema´ticas, Universidad de Chile, Beauchef 851, 8370456 Santiago, Chile, and also with the Departamento de Fı´ sica, Universidad del Valle, A.A. 25360, Cali, Colombia. Manuscript submitted September 26, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
improves the electrical and mechanical properties of the alloys, while the cold rolling strengthening leads to a depletion of the electrical conductivity,[6] which explain the large number of papers[8–13] concerning with the strengthening of alloys by precipitation hardening. A better insight in the precipitation hardening mechanism of Cu-Ni-Zn-Al alloys has been very recently achieved[14] from combined analysis of the annealing process by means of High-Resolution Electron Microscopy Transmission (HRTEM), microhardness measurements, and Differential Scanning Calorimetry (DSC). It is noteworthy to point out that DSC has been successfully used in the literature[14–23] for discriminating the successive phase transitions taking place as a function of the annealing temperature of alloys. Studying the influence that the substitution of aluminum for other metals has on the structural changes undergone during the annealing of Cu-Ni-Zn-based quaternary alloys would be of great interest for improving their mechanical properties. The scope of the present work is to study the structural evolution o
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