Papers by Author: Jong Won Kum

Abstract: In the present work, Cu-TiB2 nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.%TiB2 powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.%TiB2 composites. TiB2 particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at 650-750°C were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to 950°C for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu-TiB2 composite showed good thermal stability at eleveated temperature.

Abstract: Dispersion-strengthened copper with TiB2 was produced by ball-milling and spark plasma sintering (SPS).Ball-milling was performed at a rotation speed of 300rpm for 30 and 60min in Ar atmosphere by using a planetary ball mill (AGO-2). Spark-plasma sintering was carried out at 650°C for 5min under vacuum after mechanical alloying. The hardness of the specimens sintered using powder ball milled for 60min at 300rpm increased from 16.0 to 61.8 HRB than that of specimen using powder mixed with a turbular mixer, while the electrical conductivity varied from 93.40% to 83.34%IACS. In the case of milled powder, hardness increased as milling time increased, while the electrical conductivity decreased. On the other hand, hardness decreased with increasing sintering temperature, but the electrical conductiviey increased slightly