MICROSTRUCTURE OF POLYCRYSTALLINE ALUMINUM NITRIDE FORMED IN SHOCK-WAVES

Shock wave treatment of aluminum nitride particles produces compacted specimens with a density equal to 0.93 to 0.94 of the theoretical. An examination of the microstructure using thin foil transmission electro n microscopy indicates that polycrystalline AlN forms under these cond itions as a result of structural transformations that are typical of A lN sintering at high temperatures and pressures due to static compress ion, and particularly, plastic deformation, relaxation dislocation tra nsformations, primary and collective recrystallization. Plastic deform ation of AlN is achieved by means of full basal dislocations which des cribe both the absence of deformation polytypism and the transition to the sphalerite modification.