Mechanical, tribological and electrical properties of ZrB2 reinforced Cu processed via milling and high-pressure hot pressing

The present work investigates the effect of (0-10 wt%) ZrB2 reinforcement on densification, mechanical, tribological and electrical properties of Cu. The consolidation of Cu-ZrB2 samples was carried out using a hot press (temperature: 500 degrees C, pressure: 500 MPa, time: 30 min, vacuum pressure: 1.3 x 10(-2) mbar). The bulk density of the hot-pressed Cu composites decreased from 8.84 g/cc to 8.16 g/cc and the relative density of samples lowered from 98.6% to 92.1% with the addition of ZrB2. The incorporation of hard ZrB2 (up to 10 wt%) improved the hardness of Cu (1.32-2.55 GPa). However, the yield strength and compressive strength of Cu composites increased up to 5 wt% ZrB2, and further addition of ZrB2 lowered its strength. The yield strength of Cu samples varied from 602 to 672 MPa and the compressive strength between similar to 834 and 971 MPa. On the other hand, the coefficient of friction (COF) (from 0.49 to 0.18) and wear rate (from 49.3 x 10(-3) mm(3)/Nm to 9.1 x 10(-3) mm(3)/Nm) of Cu-ZrB2 samples considerably decreased with the addition of ZrB2. Significantly low wear was observed with Cu-10 wt% ZrB2 (Cu-10Z) samples, which is 5.41 times less than pure Cu. As far as the wear mechanisms are concerned, in pure Cu, continuous chips (wear debris) were formed during sliding wear by plowing. Whereas the major amount of material loss was occurred due to the plowing mechanism with discontinuous and short chip formation for Cu-ZrB2 composites. The electrical conductivity of Cu-ZrB2 samples decreased from 75.7% IACS to 44.1% IACS. In particular, Cu with ZrB2 (up to 3 wt%) could retain the conductivity of 66.8% IACS. This study reveals that the addition of ZrB2 (up to 3 wt%) is advantageous to have a good combination of properties for Cu.