Characterization of Dispersion Strengthened Copper with 3 wt percent Al_2O_3 by Mechanical Alloying

摘要

The copper matrix has been dispersion strengthened with 3wt. percent Al_2O_3 by mechanical alloying. Commercial alumina powder with an average particle size of 0.75 mu m was used for alloying. The mechanical alloying process was performed in. a planetary ball mill up to 20h in air. After milling all powders were treated in H_2 at 400 deg C for 1h, and finally hot pressing was used for compaction (800 deg C, 3h, Ar). Structure observations revealed a lamellar structure (Al_2O_3 particles largely restricted to interlamellar planes ''between adjacent copper lamellae) accompanied also by structure refinement. These structural changes were mostly completed in the early stage of milling, and retained after compaction. Micro hardness was found to progressively increase with milling time. So, after 5h of milling the micro hardness of the Cu+3twt percent Al_2O_3 compact was 1540MPa, i.e. 2.5 times greater than for the as-received electrolytic copper powder (638MPa) compacted under identical conditions, while after 20h of milling it was 2370 MPa. However, after exposing the tested compact at 800 deg C up to 5h, the achieved hardening effect vanished.