The methods of optical and electron diffraction microscopy are used to study the evolution of phase composition and defect structure in hard alloy WC-steel 100G13 after dynamic loading. Both stable and metastable austenite (the binding phase) are seen in the alloy after such loading. The martensitic transformation γ → e is seen along with slip in the case of the metastable state, which makes it possible to significantly reduce the scale of plastic deformation of the binder and redistribute the external load onto particles of the reinforcing phase. Microcracks form a special structure in this case, and the integrity of the specimen is maintained up to high loading rates.