Nanostructured steels

Superior strength of carbon steels

Severe plastic deformation allows to  produce  in carbon steels a nanocomposite structure: a homogeneous fine –grained ferritic matrix where highly dispersed cementite particles are located. This leads to the enhancement of strength characteristics up to values typical for high-strength steels and exceeding the strength of quenched steel. The obtained microstructure is characterized by an increased thermal stability.

Properties of steel 45:

State σв, MPa σ0.2, MPa δ, % HV, GPa
As-received state (hot pressed) 863 770 7 3
Quenching (martensite) 2192 2000 0.4 8.15
SPD (nanocomposite) 2649 2397 3 9.81

Transformation of the martensitic phase to nanocomposite

High-strength state of stainless steels

A change in the temperature to severe plastic deformation leads to the producing of  different phase compositions in steel:  from a fully austenite microstructure to 80 % martensite. Both of these structure types ensure an enhanced strength of steel, while maintaining high ductility. 

The producing of a high-strength state in carbon and corrosion-resistant steels, resulting from severe plastic deformation, is conditioned by a change in the ratio between the contributions of different strengthening mechanisms in favor of grain boundary strengthening conditioned by the formation of an ultrafine-grained structure.
Main publications:

1.  Yu. Ivanisenko, W. Lojkwski, R.Z. Valiev, H.-J. Fecht,  The mechanism of formation of nanostructure and dissolution of cementite in a pearlitic steel during high pressure torsion, Acta Mater. 51 (2003), p. 5555-5570.
2.  M.V. Karavaeva,  S.K. Nurieva,  N.G. Zaripov,  A.V. Ganeev,  R.Z. Valiev, Microstructure and  mechanical properties of medium-carbon steel subjected to svere plastic deformation, Metallovedenie i Termicheskaya Obrabotka Metallov, 2012, No. 4, p. 3-7 (in Russian).
3.  R.Z. Valiev,  G.V. Klevtsov,  N.A. Klevtsova,  M.V. Fesenyuk,  M.R. Kashapov,  M.V. Karavaeva,  A.G. Raab,  A.V. Ganeev, Effect of the regimes of equal-channel angular pressing and subsequent heating on the strength and fracture mechanism of steel 10.  Deformatsiya i Razrushenie Materialov,  No.  1, 2013, p. 21-25 (in Russian).