The paper analyzes the effect of severe plastic deformation on the structure, mechanical and thermal properties of a Zr_42.5Сu_42.5Al₁₀Fe₅ alloy. It was found that high pressure torsion induces phase separation of an amorphous matrix and causes formation of a complex structure containing nanocrystalline particles. The precipitation of nanocrystals leads to a change in the composition of the amorphous matrix and changes in the crystallization process and characteristic temperatures of the alloy. It is shown in the work that high pressure torsion significantly increases the hardness of the material, which is associated with the formation of nanocrystals in the structure and elastic stresses.