Precipitation of AlN in a commercial hot-pressed boron carbide

TEM observations have provided insight into the processing and microstructural evolution of a commercial hot-pressed boron carbide. Fine dispersions of nano-scale AlN precipitates and individual submicron AlN precipitates were observed in a modest fraction of the grains. The nano-precipitates were found to be coherent with a well-defined crystallographic relationship to the matrix. The chemistry, size and distribution of both types of precipitates and the coherency of the nano-precipitates indicate that both intragranular homogeneous and heterogeneous precipitation occurred during cooling.