Formation mechanism of intragranular structure in nano-composites

The effect of sintering process and ZrO2 contents on formation of intragranular ZrO2 in Al2O3 matrix was investigated with alpha-Al2O3 micro-powders and ZrO2 nano-powders as original materials. It is found that the second-phase particles coalesce with the growth of matrix grains during sintering. The process conditions that benefit the growth of matrix grains benefit the formation of intragrains. The formation procedure of intragrains could be described as follows. At first, the particles are driven to agglomerate during densification of the matrix. Some particles move along with the migration of the matrix grain boundaries and tend to further gather, then become intergrains. Those gripped between the matrix grain boundaries become intragrains during the growth of matrix grains.