V. F. Terent’ev

Structure and fatigue properties of 08Kh18N10T steel after equal-channel angular pressing and heating

The structure of corrosion-resistant austenitic 08Kh18N10T steel is studied after equal-channel angular pressing (ECAP), heating, and subsequent cyclic tests. After ECAP, an oriented mainly subgrain structure with a structural element size of 100–250 nm and a high fraction of deformation twins forms in the austenite of the steel, and 42 vol % of lath martensite appears. Dynamic twinning, martensitic transformation, dynamic recovery, and even recrystallization take place in the 08Kh18N10T steel during cyclic deformation in the course of fatigue tests according to the scheme of repeated tension. The fatigue strength increases after ECAP due to the refinement and twinning of an austenite structure and the appearance of martensite. The fatigue limit is maximal after ECAP and heating at 550°C for 20 h due to a high annealing twin density in a predominantly austenitic recrystallized matrix, intense dynamic twinning, and martensitic transformation during cyclic deformation.

Fatigue strength of a magnesium MA2-1 alloy after equal-channel angular pressing

The fatigue strength of a magnesium MA2-1 alloy is studied after annealing and equal-channel angular pressing (ECAP). The ultrafine-grained structure formed upon ECAP is shown to increase the plasticity of the material during static tension, to decrease the cyclic life to failure, and not to decrease the fatigue limit. The mechanisms of crack nucleation and growth during cyclic deformation are investigated.

Fatigue characteristics of auto body sheet steels

The static and cyclic mechanical properties of a dual-phase steel and a TRIP steel having a comparable yield strength are studied. The effect of deformation and subsequent aging on the fatigue strength of the dual-phase steel is investigated, and the fractographic features of the fatigue fracture are analyzed.

Effect of equal-channel angular pressing on the fatigue strength of titanium and a zirconium alloy

The static and fatigue strength of commercial-purity VT1-00 titanium and a Zr-2.5% Nb alloy subjected to equal-channel angular pressing (ECAP) are studied. The formation of a submicrocrystalline structure after ECAP is shown to result in significant hardening, an increase in the fatigue life at high stress amplitudes, and an increase in the fatigue limit as compared to the annealed state. The mechanisms of fatigue fracture of the materials in various structural states are investigated.

Static and cyclic strength of austenitic corrosion-resistant cast Cr-Ni-Mn-Mo-N steel

The resistance to cyclic loading of high-nitrogen corrosion-resistant cast austenitic 05Kh22AG15N8M2FL (∼0.5% N) steel is studied for the first time (high-cycle tests of plane specimens at 20°C in air upon repeated tension). The structure of the steel, its static strength, and the fracture in regions of high- and low-cycle fatigues are investigated. It is shown that the structural state of the steel (solid-solution treatment of the as-cast and deformed steel, hot plastic deformation, and aging) and the test conditions influence the fatigue life. The results are compared with the high-cycle fatigue life of austenitic steels with 0.1–1.1% N treated for solid solution, and the fatigue limit is compared to the ultimate strength, the grain size, and the total content of nitrogen and carbon in the steels. Fractographic studies are performed for the fracture surfaces of cast 05Kh22AG15N8M2FL steel after fatigue tests.

Effect of internal nitriding on the fatigue strength of ferritic corrosion-resistant steel

The effect of internal nitriding and subsequent annealing on the mechanical properties of ferritic corrosion-resistance 08Kh17T steel has been studied during static and cyclic loading. Nitriding was shown to increase the static and cyclic strength of ferritic steel substantially and to decrease its plasticity slightly. These changes are confirmed by results of fractographic studies.

X-Ray diffraction study of the change in the structure of a VNS9-III TRIP sheet steel after static tension

The change in the phase composition of a cold-worked austenitic–martensitic VNS9-III TRIP steel after static tension at a strain rate of 0.1, 5, 7, and 10 mm/min is studied by X-ray diffraction. The steel in the initial state has the following three phases: fcc γ phase and two bcc phases (α1, α2). A high degree of preferred (211) crystallite orientation is observed for the α1 phase, and a preferred (100) orientation is observed for the α2 phase. Deformation under static tension leads to a decrease in the content of austenite (γ phase) in the steel structure at the expense of formation of deformation martensite. The lower the strain rate, the lower the volume fraction of the γ-phase: it is 46% in the initial state, 36% at a tension rate of 10 mm/min, and 18% at a tension rate of 0.1 mm/min. The γ-phase content decreases mainly due to an increase in the α1 phase content.

Cyclic strength of corrosion-resistant high-nitrogen austenitic 05Kh22AG15N8MF steel during repeated tension

The static and fatigue cyclic strength of high-strength corrosion-resistant nitrogen-bearing austenitic 05Kh22AG15N8MF steel are studied in various structural states after hot rolling at 1100°C (water quenching from 1150°C, subsequent annealing at 800°C for 1 and 10 h, and cooling in air). The maximum life and a higher fatigue limit (400 MPa) are shown to be characteristic of hot-rolled samples with a finegrained austenitic structure and numerous twins. The mechanisms of fatigue crack propagation are studied.

Fatigue Strength of Ferrite-Martensite 12% Chromium Steels EK-181, EP-823 and Vanadium Alloy V–4Ti–4Cr

Static and fatigue strength at room temperature under conditions of repeated stretching of lowactivated ferrite-martensite 12% chromium steels EK-181 (Fe–12Cr–2W–V–Ta heat treatment + aging in lead at 600°C, 3000 h), EP-823 (Fe–12Cr–W–V–Ni–Mo–Nb, annealed condition), and alloy V–4Ti–4Cr (heat treatment + aging in lead at 600°C, 3000 h) were studied. It was shown that for materials there is straight-line dependence between the level of rupture resistance values and fatigue strength. The maximum fatigue limit of 600 MPa appears in steel EK-181 after a standard heat treatment and aging in lead at 600°C, 3000 h, and the minimal one of 300 MPa is observed in vanadium and V–4Ti–4Cr alloys. The fatigue failure mechanism is predominately of ductile character for all materials studied. The fatigue cracking originates near the surface and in some cases clustering of nonmetallic inclusions is the place of origin. The fatigue crack propagation is related to formation of a typical striation relief. Significant distinctions in the fracture surface relief of specimens after standard heat treatment and aging in liquid lead are not observed.

Influence of the tempering temperature on the mechanical properties and the phase composition of thin sheet TRIP steel

The strength and the plasticity properties of sheet high-strength austenitic–martensitic VNS9-Sh TRIP steel (23Kh15N5AM3-Sh) are studied as functions of the tempering temperature in the range 125–600°C. A nonmonotonic decease in the strength and the plasticity properties of the steel has been detected when the tempering temperature increases, and they increase in the range 300–450°C. The influence of aging processes, the precipitation of carbide, and the phase transformations in tempering on the mechanical properties of austenitic–martensitic corrosion-resistant steel is discussed.