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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An approximate solution is given for the dependence of the dislocation track length, t , around a microhardness indentation in single crystals on the load applied t o the indenter (P), the temperature (T), and the duration under load ( t ) :The assumption is made that dislocations move from the indenter in plane arrays alid that the dislocation velocity is vt m exp (-U / k T ) , where t is an effective stress, U is the activation energy.I n a definite range of parameters the equation agrees satisfactorily with the literature data and those obtained in the present work, and may be used t o estimate the dislocation mobility from the dislocation track length. The value of the ratio l/d ( d is the indentation diagonal) is constant for ionic crystals but depends on the temperature and the load in the case of covalent crystals. l is connected with the yield strengt,h ts a s Zrs = const for covalent crystals (m. = l), but 12ts = const for ionic crystals ( m > 2). Es wird eineNaherungslosung fur die Abhangigkeit der Verset,zungslLnge I urn einen Nikrohiirteeindruck in Einkristallen von der angewandten Last auf den Stempel (P), der Temperatur (T) und der Dauer der Last (t)angegeben: Z-Pm/(Zm+1)tli@m+l) exp[-UlkT(2m + l)]. Es wird dieAnnahme gemacht, dalJ Versetzungen sich vom Stempel in ebenen Anordnungen bewegen und daB die Versetzungsgeschwindigkeit wt l ) l exp (-U / k T ) ist. u-obei s eine effektive Spannung und U die Aktivierungsenergie ist. I n einem definierten Bereich von Parametern stimmt die Gleichung befriedigend mit Literaturwerten uberein und solchen, die in der vorliegenden Arbeit erhalten werden, und kann zur Berechnung der Versetzungsbeweglichkeit a u s der Lange des Versetzungspfades benutzt werden. Der Wert des Verhaltnisses Z/d (d ist die Eindruckdiagonale) ist fur Ionenkristalle konstant, hangt jedoch von der Temperatur und Last im Fall der kovalenten Kristalle ab. l ist mit der FlulJstarke ts wie Is, = const fur kovalente Kristalle ( m z l), jedoch wie Pt, z const fur Ionenkristalle ( m > 2) verknupft.

A test method procedure for constructing stress-strain curves by indentation of brittle and low plastic materials under temperature ranging from 20 to 900°C was developed recently by Yu. Milman, B. Galanov et al. According to this test method procedure stress-strain curves σ - Є for Si, Ge, SiC, TiB2 and WC/Co hard alloy were constructed in the above temperature region and mechanical parameters such as elastic point, σe, yield stress, σs, etc. were extracted by using the measurement results obtained by a set of trihedral pyramid indenters with different angles at the tip, γ1, ranging from 45 to 85°C