Spark plasma sintering mechanisms of the Al-Zn-mg-cu alloys and TiB2/Al-Zn-mg-cu composites

Abstract In the present work, spark plasma sintering experiments were conducted on the atomized Al-Zn-Mg-Cu alloy powders and TiB2/Al-Zn-Mg-Cu composite powders under different temperatures. It is aimed to study the effect of the introduced TiB2 particles on the densification mechanisms and microstructural evolutions, the result of which would serve to guide the fabrication of dense compacts with fine grains and precipitates. The sintering mechanisms were analyzed by correlating microstructural observations with sintering laws. In genral, the power-law creep process is the mass transfer mechanism leading to densification. The densification of the alloy powders was found to proceed by grain boundary sliding accommodated by surface and grain boundary diffusion of the alloy elements, whereas the densification of the composite powders was found to proceed by grain boundary sliding accommodated by bulk diffusion.The introduced TiB2 particles accelerate the densification process at the initial sintering stage due to the enhanced resistivity at powder contacts and the increased contribution from electromigration. Meanwhile, the TiB2 particles adversely affect the densification process due to the segregation of solute elements at the facets of the TiB2 particles.