Effect of Chromium Behavior on Mechanical and Electrical Properties of P/M Copper-Chromium Alloy Dispersed with VGCF

Authors: Hisashi Imai, Kuan-Yu Chen, Katsuyoshi Kondoh, Hung-Yin Tsai, Junko Umeda

Abstract:

Microstructural and electrical properties of Cu-chromium alloy (Cu-Cr) dispersed with vapor-grown carbon fiber (VGCF) prepared by powder metallurgy (P/M) process have been investigated. Cu-0.7 mass% Cr pre-alloyed powder (Cu-Cr) made by water atomization process was used as raw materials, which contained solid solute Cr elements in Cu matrix. The alloy powder coated with un-bundled VGCF by using oil coating process was consolidated at 1223 K in vacuum by spark plasma sintering, and then extruded at 1073 K. The extruded Cu-Cr alloy (monolithic alloy) had 209.3 MPa YS and 80.4 IACS% conductivity. The extruded Cu-Cr with 0.1 mass% VGCF composites revealed a small decrease of YS compared to the monolithic Cu-Cr alloy. On the other hand, the composite had a higher electrical conductivity than that of the monolithic alloy. For example, Cu-Cr with 0.1 mass% VGCF composite sintered for 5 h showed 182.7 MPa YS and 89.7 IACS% conductivity. In the case of Cu-Cr with VGCFs composites, the Cr concentration was observed around VGCF by SEM-EDS analysis, where Cr23C6 compounds were detected by TEM observation. The amount of Cr solid solution in the matrix of the Cu-Cr composites alloy was about 50% compared to the monolithic Cu-Cr sintered alloy, and resulted in the remarkable increment of the electrical conductivity.

Keywords: Powder metallurgy Cu-Cr alloy powder, vapor-grown carbon fiber, electrical conductivity.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1106947

References:

[1] A. Lee, N. Grant. Properties of Two High Strength, High Temperature, High Conductivity Cu Base Alloys. Materials Science and Engineering, 60, 213-223 (1983).
[2] N. Khandoker et al. “Tensile Strength of Spinnable Multiwall Carbon Nanotubes”, Procedia Engineering, 10, 2572-2578 (2011).
[3] S. Xie et al., “Mechanical and Physical Properties on Carbon Nanotube”, Journal of Physics and Chemistry of Solids, 61, 1153-1158 (2000).
[4] K. Kondoh et al., “Microstructural and Mechanical Analysis of Carbon Nanotube Reinforced Magnesium Alloy Powder Composites”, Materials Science & Engineering A, 527, 4103-4108 (2010).
[5] S. Li et al., “Powder Metallurgy Ti-TiC Metal Matrix Composites Prepared by In-situ Reactive Processing of Ti-VGCFs System”, Carbon, 61, 216-228 (2013).
[6] Y. Shimizu et al., “Multi-Walled Carbon Nanotube-Reinforced Magnesium Alloy Composites”, Scripta Materialia, 58, 267-270 (2008).
[7] D. Laughlin, J. Cahn, “Spinodal Decomposition in Age Hardening Cu-Titanium Alloys”, Acta Materialia, 23, 329-339 (1975).
[8] A. Poter, A. Thompson, “On the Mechanism of Precipitation Strengthening in Cu-Ti Alloys”, Scripta Materialia, 18, 1185-1188 (1984).
[9] K. Maki et al., “Solid-solution Cu alloys with high strength and high electrical conductivity”, Scripta Materialia, 68 (2013), 777-780.
[10] S. Nagarjuna et al., “Effect of Prior Cold Work on Mechanical Properties, Electrical Conductivity and Microstructure of Aged Cu-Ti Alloys”, Journal of Materials Science, 34, 2929-2942 (1999).
[11] S. Nagarjuna et al., “On the Variation of Mechanical Properties with Solute Content in Cu-Ti Alloys”, Materials Science and Engineering A, 259, 34-42 (1999).
[12] S. Semboshi et al., “Microstructural Evolution of Cu-1 at % Ti Alloy aged in a Hydrogen Atmosphere and Its Relation with the Electrical Conductivity”, Ultramicroscopy, 109, 593-598 (2009).
[13] S. Suzuki et al., “Electrical and Thermal Conductivities in Quenched and Aged High-Purity Cu-Ti Alloys”, Scripta Materialia, 48, 431-435 (2003).
[14] T. Oku et al., “Effects of Titanium Addition on the Microstructure of Carbon/Cu Composite Materials”, Solid State Communications, 141, 132-135 (2007).
[15] H. Imai et al., “Microstructural and Electrical Properties of Cu-titanium Alloy Dispersed with Carbon Nanotubes via Powder Metallurgy Process”, Materials Transactions, 55, 3, 522-527, (2014).
[16] H. Imai et al., “Effect of Chromium Precipitation on Machinability of Sintered Brass Alloys Dispersed with Graphite Particles”, Materials Transactions, 52, 7, 1426-1430, (2011).
[17] M.S. Dresselhaus et al., “Raman Spectroscopy of Carbon Nanotubes,” Physics Reports, 409, 47-99, (2005).
[18] M. Small et al. “Calculation and evaluation of the Gibbs energies of formation of Cr3C2, Cr7C3, and Cr23C6”, Metallurgical and Materials Transaction A, 12, 1389-1396, (1981).