The urgency of the discussed issue is caused by the need to find a new technology of obtaining aluminum nitride. The main aim of the study to justify the possible mechanism of aluminum nitride crystal formation under thermal explosion during combustion of aluminum nanopowder in air and to propose the phenomenology model of these processes. The methods used in the study: X-ray diffraction studying with high time resolution (synchrotron radiation), SEM-microscopy, thermodynamic calculation. The results: It was established experimentally during combustion of aluminum nanopowder in air under thermal explosion the micro size monocrystals are formed in homogeneous magnetic field and elongated nonlinear crystals with faceting are formed in inhomogeneous magnetic field. The authors have proposed the phenomenology model of aluminum nitride crystal formation under thermal explosion during aluminum nanopowder combustion. The faceting crystal formation is the result of magnetic field influence on stabilization of combustion product and their subcooling. Monocrystals grow in heat wave as a result of transition of X-ray amorphous phase in stable monocrystal condition.