Effect of high energy milling and compaction pressure on density of a sintered Nb-20%Cu composite powder

This work reports the influence of the use of composite particles of composition Nb-20 wt.%Cu and the compaction pressure on density and structure of sintered pieces. High energy milling is used to produce the composite powders. Milling times of 2, 20, 50 and 100 h were used. The powders were pressed under 200, 300, 400 and 500 MPa and sintered at 1100 °C for 60 min. After sintering, density was measured and cross sections of the structures were observed under SEM. The electric conductivity was also measured. Density and electric conductivity behave similarly with respect to compaction pressure and milling time. Cracks are created during pressing and ejection of the green pieces from the die. The cracks are mainly present in samples prepared with powders milled longer and are not closed by sintering. On the other hand, sintering can close most of the pores formed by the composite particles.