Strengthening effects in precipitation and dispersion hardened powder metallurgy copper alloys: Fid-Bau Portal

Strengthening effects in precipitation and dispersion hardened powder metallurgy copper alloys

Ružić, J. / Stašić, J. / Rajković, V. / Božić, D.

Highlights ► Preparation and study of strengthening effects in Cu–Ti, Cu–TiB2 and Cu–Ti–TiB2 alloys. ► High strengthening of the Cu–Ti due to modular structure and precipitation of Cu4Ti(m). ► High hardness in Cu–TiB2 due to finely distributed TiB2 after mechanical alloying. ► Hardening in the Cu–Ti–TiB2 due to modular structure, Cu4Ti(m), and TiB2 dispersoids. ► The highest hardness in Cu–Ti–TiB2 owing to combined hardening mechanism.

Abstract The hardening of copper and copper alloy matrix using powder metallurgy (PM) techniques and different ways for dispersoids formation, as well as analysis of their single and combined effects on the strength of obtained material at room and elevated temperatures, have been presented and discussed. Gas atomized Cu–3.8wt.%Ti and Cu–0.6wt.%Ti–2.5wt.%TiB2 (Cu–Ti–TiB2) powders and mechanically alloyed powder Cu–4wt.%TiB2 were used as starting materials. The powders were consolidated by hot isostatic pressing (HIP) and hot pressing (HP). Optical, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX), as well as transmission electron microscope (TEM) were used for microstructure characterization of the compacts. High strengthening of the Cu–Ti compacts was achieved by thermal treatment (aging) as a consequence of the development of modular structure and precipitation of metastable Cu4Ti(m). Hardening in the Cu–Ti–TiB2 compacts is due to simultaneous influence of the following factors: the development of modular structure, precipitation of metastable Cu4Ti(m), and the presence of TiB2 dispersoid nanoparticles. In case of Cu–TiB2 compacts, high starting values of hardness and hardness on the elevated temperatures result from the presence of finely distributed TiB2 particles in copper matrix obtained by mechanical alloying. Cu–Ti–TiB2 composite yields much higher hardness values compared with the binary Cu–Ti alloys, owing to primary TiB2 dispersions formed during atomization. Separation of metastable Cu4Ti precipitate and the presence of significantly finer TiB2 particles in the copper matrix are the reason for higher hardness values at peak temperatures (400–500°C) in multiple-hardened copper alloy compared to the dispersion-hardened.