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The mechanism of microhardness print forming in diamond‐structure crystals is considered to be the result of a local phase transition under the indenter with the formation of a metallic phase due to the high hydrostatic pressure generated in this case. It is shown that at the temperature T < 0.3 to 0.4 Tml, where the microhardness Hv is weakly temperature‐dependent, one has Hv ≈ Pc(Pc transition pressure). In GaAs crystals, where Hv ≪ Pc, the athermal part in the hardness‐temperature curve was not observed. It is shown as well that at the moment when the indenter entering the crystal is stopped there is a thin layer around it which still contains the metallic phase with high electrical conduction. The estimated thickness of the layer is ≈ 0.05 μm. The plastic deformation is supposed not to proceed at this moment because of the friction forces which oppose the squeezing‐out of the metallic layer.

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