Distribution Of Interstitial Atoms Research Articles

Влияние фазовых превращений в процессе электронно-лучевой 3D-печати и последующей термической обработки на закономерности пластической деформации и разрушение образцов высокоазотистой Cr-Mn-стали

We investigated the phase composition, plastic deformation and fracture micromechanisms of Fe-(25-26)Cr-(5-12)Mn-0.15C-0.55N (wt. %) high-nitrogen chromium-manganese steel. Obtained by the method of electron-beam 3D-printing (additive manufacturing) and subjected to a heat treatment (at a temperature of 1150°C following by quenching). To establish the effect of the electron-beam 3D-printing process on the phase composition, microstructure and mechanical properties of high-nitrogen steel, a comparison was made with the data for Fe-21Cr-22Mn-0.15C-0.53N austenitic steel (wt. %) obtained by traditional methods (casting and heat treatment) and used as a raw material for additive manufacturing. It was experimentally established that in the specimens obtained by additive manufacturing method, depletion of the steel composition by manganese in the electron-beam 3D-printing and post-built heat treatment contributes to the formation of a macroscopically and microscopically inhomogeneous two-phase structure. In the steel specimens, macroscopic regions of irregular shape with large ferrite grains or a two-phase austenite-ferrite structure (microscopic inhomogeneity) were observed. Despite the change in the concentration of the basic elements (chromium and manganese) in additive manufacturing, a high concentration of interstitial atoms (nitrogen and carbon) remains in steel. This contributes to the macroscopically heterogeneous distribution of interstitial atoms in the specimens - the formation of a supersaturated interstitial solid solution in the austenitic regions due to the low solubility of nitrogen and carbon in the ferrite regions. This inhomogeneous heterophase (ferrite-austenite) structure has high strength properties, good ductility and work hardening, which are close to those of the specimens of the initial high-nitrogen austenitic steel used as the raw material for additive manufacturing.

Вплив оксиду ітрію на розподіл міжвузлових атомів у порошковому залізі

Вплив оксиду ітрію на розподіл міжвузлових атомів у порошковому залізі

Unstable Plastic Flow and Mechanical Properties of Substitutional Iron Alloys with Polygonized Ultrafine Grain Microstructure

A study was made of the strength-ductility relationship in substitutional iron alloys with ca. 2at% Al, Si, Ti, Cr, Mn, Ni, or Mo at ambient and low temperatures. They were cold rolled and annealed to attain either recovered or partially recrystallized structure composed largely of Polygonized subgrains of 1μm or less. It was shown that the deformation behavior in tension of these ultrafine grained iron alloys was characterized by a very small elongation due to the occurrence of plastic instability. It was found, however, that some species of solute elements manifested a remarkable effect of increasing the elongation, and furthermore, that the effect was filly maintained in the presence of Nb, which was added to retain high strength pertaining to recovered state as a result of its well-known effect on retarding recrystallization.It was suggested that the unstable plasticity in tension was closely related to the formation of the Luders bands. Various factors which may affect the Luders strain, i.e., the mode of slip, dislocation structure, and distribution of interstitial atoms, were investigated in terms of the influence of substitutional solutes. It was shown that a high dislocation multiplication rate was the most distinctive feature of the alloys exhibiting a large elongation at low temperatures.

ポリゴン化した超微細粒組織を有する置換型固溶鉄合金の不安定変形挙動と機械的性質

A study was made of the strength-ductility relationship in substitutional iron alloys with ca. 2at% Al, Si, Ti, Cr, Mn, Ni, or Mo at ambient and low temperatures. They were cold rolled and annealed to attain either recovered or partially recrystallized structure composed largely of Polygonized subgrains of 1μm or less. It was shown that the deformation behavior in tension of these ultrafine grained iron alloys was characterized by a very small elongation due to the occurrence of plastic instability. It was found, however, that some species of solute elements manifested a remarkable effect of increasing the elongation, and furthermore, that the effect was filly maintained in the presence of Nb, which was added to retain high strength pertaining to recovered state as a result of its well-known effect on retarding recrystallization.It was suggested that the unstable plasticity in tension was closely related to the formation of the Luders bands. Various factors which may affect the Luders strain, i.e., the mode of slip, dislocation structure, and distribution of interstitial atoms, were investigated in terms of the influence of substitutional solutes. It was shown that a high dislocation multiplication rate was the most distinctive feature of the alloys exhibiting a large elongation at low temperatures.

Distribution of interstitial atoms over octahedral pores of ordered alloys with CuAu structure

The authors consider the kinetics of processes of redistributions of interstitial atoms over the octahedral interstices in ordered alloys of the CuAu type as a result of a sudden change in temperature. The relaxation time of the process is determined and the equilibrium concentrations of interstitial atoms are found. These quantities are considered as functions of the degree of long-range order, the alloy composition, and the temperature.

An application of the Schoeck theory to the cold-work internal friction peak in iron

The metallurgical usefulness of the cold-work peak has been limited by an inadequate understanding of the mechanism of the peak. Our analysis examines the predictions of the Schoeck theory of the cold-work peak and compares these predictions to some experimental results obtained from α-iron. The distribution of interstitial atoms between lattice and dislocation sites is treated by Fermi-Dirac statistics. The most reasonable relaxation times are predicted by the Schoeck formulation when the mobility term is characterized by an activation energy which is the sum of the activation energy for lattice diffusion and the binding energy of the interstitial to the dislocation. An expression is derived which predicts the activation energy determined in a typical internal friction experiment. The predictions are consistent with experimental observations. Experimental peak position and relaxation strength data are analyzed and found to yield reasonable active (contributive) dislocation densities.

Thermodynamic Behavior of Dilute Solutions of Hydrogen and Deuterium in Titanium and Zirconium

An investigation has been made of the partial free energy of very dilute solutions of hydrogen and deuterium in the high-temperature, body-centered cubic forms of titanium and zirconium. Anomalous behavior is found which manifests itself as a departure from Sieverts' law. Analysis of the results indicates that there is a strongly marked minimum in the partial enthalpy at hydrogen and deuterium concentrations of about 1 at.% in both metals. This may be associated with a departure from complete randomness in the distribution of interstitial atoms in the solution.