Fabrication of Cu-TiB2 Composite by in-situ Process with Electro Magnetic Stirring

초록

Recently, a number of studies on fabrication of the copper matrix composite materials for electrode materials with good mechanical properties and electric properties at high temperature have been performed. The copper matrix composites has been generally produced by P/M process. However, this process is complex and the cost is high. More recently, alumina dispersed copper alloy with a good thermal property was studied but the fabrication process is also complicated. In this study, the TiB2 dispersed copper composite material showing good thermal and electric properties was fabricated by in-situ process which is relatively economical. In the process, electromagnetic stirring was applied to ensure to distribute TiB2 uniformly. Master alloy of Cu-Ti and Cu-B were prepared by arc melting. The target composition was Cu-3~10vol.%TiB2. The as-cast billet was extruded at 800℃ with an extrusion ratio of 8:1 and then cold rolled to 90% of compression ratio. The as-rolled material was heated at 200~700℃ for 1hour. The SEM and XRD observation were carried out to observe microstructure. In order to investigate mechanical properties, tensile tests and vickers hardness tests were performed. Electrical conductivity was also tested. From the results of the microstructure observation of extruded materials, TiB2 particles sized 500~2㎛ were observed and clusters of them were also found partially. For 90% rolled materials, the growth of TiB2 particles was not observed though it was heated. It suggests that TiB2 is stable at high temperature. However, hardness and tensile strength of Cu-TiB2 composites decreased gradually during heat treatment at 200~400℃ due to softening of copper matrix. However, above 400℃ of heat treatment, no further decrease in hardness and tensile strength was found. Hardness, tensile strength and electrical conductivity of Cu-3.0vol.%TiB2 composites material after fully softening treatment were 95HVm, 350MPa and 81.2%IACS, respectively.