Effects of Zr element on the microstructure and mechanical properties of B4C/Al composites fabricated by melt stirring method

In this study, the addition of Zr element (K2ZrF6) was employed to improve the wettability, inhibit the serious chemical reaction of B4C to Al, and uniformly disperse the B4C particles in the Al melt, during the fabrication of B4C/Al composites via melt stirring method. And the particle distribution, interface microstructure and mechanical properties of the fabricated composites were further investigated. The metallography observation shows that the B4C particles could be effectively introduced to the Al melt with the addition of Zr element, while there were few B4C particles observed in the composites without Zr addition. The XRD analysis indicates that the ZrB2 and ZrC peaks arise with the addition of Zr, where the ZrB2 and ZrC have better chemical stabilization and wettability than the B4C ceramic particles. The SEM, EDS, TEM and SAED analysis shows that the ZrB2 and ZrC interface layer with a thickness of about 200-350 nm on the B4C surface was formed, which could avoid the serious chemical reaction and improve the wettability of B4C to Al, simultaneously. In addition, the easy introduction of B4C particles to the Al melt with K2ZrF6, the formation mechanism of ZrB2 and ZrC layer, and mechanical properties of the composites were also discussed.