Preparation and arc erosion characteristics of ultrafine crystalline CuCr50 alloy by MA-SPS

Abstract

The ultrafine crystalline CuCr50(Cr 50 wt%) alloys were fabricated by a combination of mechanical alloying and spark plasma sintering process. The effects of milling time on crystallite size and solid solubility of the CuCr50 composite powders were investigated. The results showed that crystallite size of powders decreases gradually and solid solubility of Cr in Cu was extended with increasing milling time. The minimal crystallite size about 10 nm and the maximum solid solubility about 8.4 at% (i e, 7 wt%) were obtained at 60 h. The microstructure of ultrafine crystalline CuCr50 alloy was analyzed by SEM and TEM, which contains two kinds of size scale Cr particles of 2 μm and 50-150 nm, distributing homogeneously in matrix, respectively. The arc erosion characteristics of ultrafine crystalline CuCr50 alloy were investigated by the vacuum contact simulation test device in low D.C. voltage and low current (24 V/10 A). A commercial microcrystalline CuCr50 alloy was also investigated for comparison. Experiments indicate that the cathode mass loss of ultrafine crystalline CuCr50 contact material is higher than that of microcrystalline CuCr50 material, but its eroded surface morphology by the arc is uniform without obvious erosion pits. While the surface of microcrystalline CuCr50 contact is seriously eroded in local area by the arc, an obvious erosion pit occurred in the core part. Therefore, the ability of arc erosion resistance of ultrafine crystalline CuCr50 alloy is improved compared to that of microcrystalline CuCr50 material.

Keywords

mechanical alloying / spark plasma sintering / ultrafine crystalline / CuCr50 alloys / arc erosion characteristics

References

[1] Slade P G. Advance in Materials Development for High Power Vacuum Interrupter Contacts[J]. IEEE Trans. Compon. Packag. Manuf. Technol. Part A, 1994, 17(1): 96-106.

[2] Rieder W F, Schussek M, Glatzle W, et al. The Influence of Composition and Cr Particle Size of Cu/Cr Contacts on Chopping Current, Contact Resistance and Breakdown Voltage in Vacuum Interrupters[J]. IEEE Trans. on CPMT, 1989, 12(2): 273-283.

[3] Wang Y P, Ding B J. The Preparation and the Properties of Microcrystalline and Nanocrystalline CuCr Contact Materials[J]. IEEE Trans. on CPMT., 1999, 22(2): 467-472.

[4] Feng Y, Zhang C Y, Yang Z M, et al. Effects of Nanocrystallization of Cucr Contact Materials on Characteristics of Vacuum Discharge[J]. Ordnance Mater. Sci. Eng., 2005, 28(5): 19-22.

[5] Yang Z M, Zhang Q L, Zhang C Y, et al. Influence of Microstructure of CuCr25 Cathode on the Motion of Vacuum Arc Spots[J]. Phys. Lett. A, 2006, 353(1): 98-100.

[6] Wang Y P, Zhang C Y, Zhang H, et al. Effect of the Microstructure of Electrode Materials on Arc Cathode Spot Dynamics[J]. J. Phys. D, Appl. Phys., 2003, 36(21): 2649-2656.

[7] Fu G Y, Niu Y, Gesmundo F. Microstructural Effects on the High Temperature Oxidation of Two-phase Cu-Cr Alloys in 1 atm O₂[J]. Corros. Sci., 2003, 45(3): 559-574.

[8] Lahiri I, Bhargava S. Compaction and Sintering Response of Mechanically Alloyed Cu-Cr Powder[J]. Powder Technol., 2009, 189(3): 433-438.

[9] Sheibani S, Heshmati-Manesh S, Ataie A. Structural Investigation on Nano Crystalline Cu-Cr Supersaturated Solid Solution Prepared by Mechanical Alloying[J]. J. Alloy. Compd., 2010, 495(1): 59-62.

[10] Shi K Y, Xue L H, Yan Y W, et al. Effects of Mechanical Alloying Parameters on the Microstructures of Nanocrystalline Cu-5 wt% Cr Alloy[J]. J. Wuhan University of Tech. -Mat. Sci. Ed., 2013, 28(1): 192-195.

[11] Aguilar C, Martinez V d P, Palacios J M, et al. A Thermodynamic Approach to Energy Storage on Mechanical Alloying of the Cu-Cr System[J]. Scr. Mater., 2007, 57: 213-216.

[12] Hull D, Bacon D J. Introduction to Dislocations[M], 1984 Oxford: Pergamon Press.

[13] Wang Q F, Cui S M, Zhang R L. Characteristics of Cathode Spot Motion on Nanocrystalline CuCr25 Alloy[J]. Rare Metal. Mater. Eng., 2008, 37(4): 641-643.

[14] Feng Y, Bo T, Wang H L, et al. Influence of Nanocrystallization of CuCr25 on Spot Diffusion of Cathode by Vacuum Arc[J]. Rare Metal. Mater. Eng., 2007, 36(5): 929-932.