Enhanced combination of strength and electrical conductivity properties with CrB2 reinforced Cu matrix composites fabricated by powder metallurgy

Abstract

Generally, the severe aggregation of the strengthening phase in the metal matrix obviously weakened the strengthening efficiency. Herein, to eliminate the agglomeration phenomenon of CrB2 particle with a high-volume fraction and thus improve the mechanical properties, CrB2/Cu composites were fabricated by ball milling, hot pressure sintering and hot extrusion. And then the effects of milling time length and CrB2 aggregation state on mechanical and electrical properties were systemically studied. Moreover, the content of CrB2 particles on the mechanical and the relevant strengthening and conductive mechanisms were discussed. Microstructure results show that an increase in milling time reduced the agglomeration of CrB2 particles and enlarge the limit dispersion content from 3 to 8 vol%. Remarkably, the mechanical properties of CrB2/Cu composites increased with increasing ball milling time, while the electrical conductivity slowly declined. It is also found that the fabricated composites have higher strength than pure Cu. When the ball milling time is 20 h, an excellent combination of strength (622 MPa), elongation (12.6%), and electrical conductivity (70.56%IACS) is obtained from 5 vol% CrB2 particles, which can be attributed to the effect of uniform dispersion of CrB2 particles. Based on the experimental results, it is determined that refinement strengthening and dislocation strengthening are the main strengthening mechanisms, respectively.