- A theoretical study of the interaction between fibers and a matrix is performed, which is based on several approaches that are connected with the calculation of mixing energy in multicomponent alloys or with the calculation of the diffusion coefficients in such systems. As an example, interatomic potentials for the alloys (Al,Si)-B, (Al,Mg)-B, (Al,Cr)-B, (Al,Mn)-B and (Al,Ga.)-B are calculated. The values of the potential barrier Δu for binary alloys are compared with those in ternary systems. It is shown that alloying of a binary alloy by Si reduces the height of potential in comparison with the binary alloy. Other elements make this barrier higher.