Effect of powder characteristics on Cr internal oxidation for preparation of Cr 2 O 3 /Cu composite

Abstract

Cr O₃/Cu composite was prepared by the internal oxidation of Cu–Cr pre-alloyed powders formed by high energy milling. Effects of milling time on the internal oxidation characteristics of Cu–Cr pre-alloyed powders were also discussed in this paper. The results indicate that the degree of the internal oxidation continually increases with prolonged milling time. At the initial stage, external oxidation rather than internal oxidation occurs, resulting in coarse Cr₂O₃ particles. With further milling, the internal oxidation becomes more complete and the sizes of Cr₂O₃ particles also become finer and well distributed. The properties of the composite are therefore improved. A high quality composite specimen from Cu–1·0Cr pre-alloyed powders after 40 h milling was prepared by the internal oxidation process. The Cr₂O₃ particles with an average size of 2–5 μm in diameter and about 5–10 μm in particles space were found by a microstructure examination, and they were uniformly dispersed in the Cu matrix.