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Conclusions 1.A thermomechanical treatment with a 90% reduction below the recrystallization temperature of constructional steels with a broad range of stable austenite can develop sb=280 to 300 kg/sq.mm at d5=6% which by far exceeds the properties of these steels after ordinary or stepped hardening followed by low tempering.2.The strength of a steel thus treated increased with carbon up to 0.5% C; at still higher carbon, the tensile strength fell and the fracture was semi-brittle or brittle.3.The optimum ratio of strength and ductility after such a treatment was achieved in these steels after tempering at 100°C; at higher tempering, both strength and ductility decreased.4.An increase of the deformation from 50 to 90% during a themomechanical treatment in the zone of stable austenite below recrystallization increased the strength considerably.5.A 50% reduction in the same conditions improved greatly the ductility but rather little the strength. The advantage of such a deformation is that it can be carried out at relatively high temperatures, even above recrystallization.6.Thermomechanical processing increased the brittle strength of steel.7.Such processing is accompanied by refinement of the martensite platelets and by a substantial decrease of the areas of coherent scattering (size of blocks). The structural refinement was apparently one of the factors which increased the resistance to plastic deformation as well as the brittle strength.

1.Heating to 525–950°C after austenitizing at 1050°C reduces substantially the stability of austenite. Destabilization of austenite is explained by a depletion of the solid solution in chromium and carbon by chromium carbide precipitation.2.Prolonged holding at room temperature after austenitizing or heating at up to 500°C stabilizes the austenite. The martensitic transformation after thermal stabilization has the following peculiarities: Undercooling of the austenite down to -196°C is possible at relatively slow cooling rates; the transformation of austenite to martensite proceeds isothermally after a certain in induction period. The effect of isothermal temperature and holding time on the transformation rate is represented by a curve showing a maximum.3.These rules do not apply to an ordinary martensitic transformation of unstabilized austenite.4.Thus, in thermally stabilized steel Kh15N9Yu the martensitic transformation proceeds so as to indicate that its kinetics is determined by the thermal vibrations of the atoms.