Atomic Order and Submicrostructure in Iron Alloys at Megaplastic Deformation

The subject of the present review consists of summing up our previous results on the study of the relaxation of structure along the way (i) of atomic redistribution—in the form of short-range clustering in binary iron alloys—induced by megaplastic deformation (i.e., of super large value), and (ii) of the dissolution and precipitation of disperse nitrides and carbides in steels and intermetallics in ageing alloys. Within the capacity of the main method of executing megaplastic deformation, along with the practically important milling in ball mills and friction-providing external action, we employed high pressure torsion (HPT) in Bridgman anvils, which permitted the control of the degree, rate, and temperature of deformation action. At the local level of two nearest neighbors (one or two coordination shells in relation to an iron atom) we studied atomic mass transfer, stipulated by generation of a large number of point defects of deformation origin, and conducted a comparison with a case of irradiation by high-energy electrons. We established a change in the direction of phase transformations, as well as anomalous acceleration of the ordering and precipitation of disperse phases upon altering the temperature (T < 0.3Tmelt) and rate of deformation (from 2 × 10−2 to 8 × 10−2 s−1). We also demonstrated the possibility of regulating the ultra-fine-grained structure with solid⁻solution strengthening and dispersion hardening

Regulation of the Concentration Heterogeneity and Thermal Expansion Coefficient in the Metastable Invar FeNi_31.1 Alloy

Mössbauer spectroscopy and electron microscopy study of the active redistribution of Ni atoms during the process of polymorphous transformation α→γ in the metastable FeNi31.1 alloy revealed that slow heating (at the rate of 0.2 K/min) results in the depletion of the initial α-phase with a beneficiation of developing disperse γ-phase plates according to the equilibrium diagram. A regulation possibility of the concentration heterogeneity and austenite thermal expansion coefficient resulted from the polymorphous transformation α→γ was shown. Comparison with data of FeNi35 alloy irradiation by high-energy electrons responsible for the variation of atomic distribution and thermal expansion coefficient (owing to the spinodal decomposition) was performed

Critical Redistribution of Nitrogen in the Austenitic Cr-Mn Steel under Severe Plastic Deformation

A narrow temperature range of changes in the mechanism and kinetics of structural-phase transformations during mechanical alloying under deformation in rotating Bridgman anvils was determined by the methods of Mössbauer spectroscopy, electron microscopy, and mechanical tests in the high-nitrogen chromium-manganese steel FeMn22Cr18N0.83. The experimentally established temperature region is characterized by a change in the direction of nitrogen redistribution—from an increase in the N content in the metal matrix during cold deformation to a decrease with an increase in the temperature and degree of severe plastic deformation. The change in the direction of nitrogen redistribution is due to the acceleration of the decomposition of a nitrogen-supersaturated solid solution of austenite with the formation of secondary nanocrystalline nitrides. The presence of a transition region for the mechanism of structural-phase transitions is manifested in the abnormal behavior of the mechanical properties of steel

Dynamic properties of reactor steels Kh16N15M3T1 and Kh13V2 under shock-wave loading of submicrosecond scale

Kh16N15M3T1 and Kh13V2 reactor steels were investigated. The study was carried out using a light-gas gun with the deformation velocities ranging from 4·104 to 3·106 s-1 and shock-loading pulses in 0.05-1 μs duration range. Dependences of the spallation strength and dynamic elastic limit in a wide temperature range are obtained. The recovered specimens were used to carry out the metallography analysis

Dynamic properties of reactor steels Kh16N15M3T1 and Kh13V2 under shock-wave loading of submicrosecond scale

Kh16N15M3T1 and Kh13V2 reactor steels were investigated. The study was carried out using a light-gas gun with the deformation velocities ranging from 4·104 to 3·106 s-1 and shock-loading pulses in 0.05-1 μs duration range. Dependences of the spallation strength and dynamic elastic limit in a wide temperature range are obtained. The recovered specimens were used to carry out the metallography analysis