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hen College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing, People’s Republic of China (Received 26 April 2009; accepted 3 August 2009)

The poor wettability between ceramics and metals is a main obstacle in obtaining highperformance metal-matrix composites (MMCs) parts using direct metal laser sintering (DMLS). Rare earth (RE) elements, due to their unique physical and chemical properties, have high potential for improving laser processability of MMCs. In this work, a comparative study was performed to investigate the influence of RE–Si–Fe addition on microstructural features and mechanical properties of DMLS processed tungsten carbide (WC) particle reinforced Cu MMCs parts. It showed that by adding 3 wt% RE–Si–Fe, the WC reinforcing particles were refined, the particle dispersion state was homogenized, and the particle/matrix interfacial compatibility was enhanced. The RE–Si–Fe-containing WC/Cu MMCs parts possessed significantly elevated mechanical properties, i.e., densification level of 95.7%, microhardness of 417.6 HV, fracture strength of 201.8 MPa, and friction coefficient of 0.8. The metallurgical functions of the RE–Si–Fe additive for the improvement of DMLS quality of MMCs parts were discussed. I. INTRODUCTION

Copper (Cu) is widely used as a promising material for electrical contacts due to the excellent electrical and thermal conductivity and outstanding resistance to fatigue and corrosion.1 Nevertheless, the limited wear and arcing resistance of Cu limits its practical applications.2,3 The mechanical wear resistance can be improved significantly by incorporating a second reinforcing phase into Cu, i.e., by developing Cu-based metal-matrix composites (MMCs). These MMCs find applications as current-carrying contacts, vacuum interrupter, arcing tips, electrical discharge machining electrodes, etc.4 Particle reinforced MMCs, due to the ease of processing, lower production cost, and nearly isotropic properties as relative to fiber reinforced MMCs, are preferable for such applications. So far, the use of tungsten (W) as a reinforcing phase for Cu has been intensively studied for the preparation and consolidation of W–Cu composites. Tungsten, as a refractory metal, provides a certain degree of wear and arcing resistance when used in the form of W–Cu composites. However, owing to the mutual insolubility of W and Cu a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0419 J. Mater. Res., Vol. 24, No. 11, Nov 2009

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and the high contact angle of liquid Cu on W, significant difficulties still exist to realize a full densification of W–Cu composites.5 Furthermore, to meet the lightweight requirement in the modern electric industry, reinforcements possessing a lower density and a higher hardness than that of W are preferred in Cu-based MMCs. Recently, tungsten carbide (WC) instead of W has been used as reinforcement for MMCs for electrical contact applications