The present article considers modelling the process of electron beam synthesis of products from granules of titanic alloy BТ-6 allowing for heat capacity of phase transition. It is established that during the electron beam synthesis of products the process of transforming the powder in a liquid state with its subsequent crystallization can be described by the Stephan two-phase task. The principles of calculating an effective mode of processing are shown at the layer-by-layer melting of powder of the BT-6 titanic alloy on the basis of the mathematical model allowing for processes of heat and mass transfer. The solution to the Stefan task has allowed to define speeds of heating and cooling, fusion depth, traverse speed of moving the firm-liquid boundary into the product.