DENSIFICATION BEHAVIOR OF MECHANICALLY ALLOYED W-Cu COMPOSITE POWDERS BY THE DOUBLE REARRANGEMENT PROCESS Jin-Chun Kim, Sung-Soo Ryu, Young Do Kim and In-Hyung Moon Department of Materials Engineering, Hanyang University, Seoul 133-791, Korea (Received January 22, 1998) (Accepted in revised form May 25, 1998) Introduction Tungsten-copper(W-Cu) composites are promising materials for thermal managing applications such as microelectronic devices because of the low thermal expansion coefficient of tungsten and the high thermal conductivity of copper (1–3). These materials have been produced by conventional Cu- infiltration sintering or by liquid-phase sintering (4, 5). The full densification of W-Cu composites by liquid-phase sintering is attained mainly by the tungsten particle rearrangement due to the capillary force and surface tension of Cu-liquid phase (6, 7) as well as solid-state sintering, because W and Cu have no solubility under equilibrium condition (8). If the constituent phases are extremely fine homogeneous state, the fully dense parts with the homogeneous microstructure can be attained at the stage of particle rearrangement. To promote homogeneity, much works such as the coreduction method of the raw oxide powders (9, 10) or mechanical alloying of the element powders (11, 12) have been studied. The mechanical alloying method is the attractive one from the engineering viewpoint because the nanostructured(NS) materials can be easily synthesized in large quantities. Nevertheless, the studies of nanostructured W-Cu alloys have been focused only on the formation and the fabrication of composite powders by mechanical alloying (11–13). And there were few researches of liquid-phase sintering behavior of NS W-Cu composite powders compared to nanostructure characteristic study. The authors have recently reported on the characteristics of nanostructured W-Cu alloys produced by mechanical alloying method (14, 15). In this study, the new concept of nanosintering was suggested to explain the drastic grain growth of mechanically alloyed NS W-Cu powders during the solid-state sintering. The high sinterabilty of these mechanically alloyed NS W-Cu alloys was also obtained by liquid-phase sintering. In this present work, the enhanced sinterabilty of mechanically alloyed NS W-Cu composite powders with sintering temperature is investigated and evaluated by the combination of nanosintering and conventional liquid-phase sintering. Experimental Elemental W (99.9% purity, 4.28m) and Cu(99.5% purity, 50.42m) powders were used for raw powders in this experiment. The mechanical alloying was carried out in an attrition mill using a stainless steel vial and balls with a speed of 400 rpm. The powder charge was 20g, with balls to powders weight ratio of 60:1. The W-20wt%Cu and W-30wt%Cu composite powders were prepared by milling for 100 Pergamon Scripta Materialia, Vol. 39, No. 6, pp. 669 – 676, 1998 Elsevier Science Ltd Copyright © 1998 Acta Metallurgica Inc. Printed in the USA. All rights reserved. 1359-6462/98 $19.00 + .00 PII S1359-6462(98)00232-2 669