Correlation of the microdislocation parameters with the hardness of plastically deformed heat-resistant steels

By the methods of electron-transmission microscopy and nondestructive testing, we study basic regularities of the influence of high-temperature plastic deformation on the kinetics of hardening of 15Kh13MF and 25Kh1M1F heat-resistant steels. The difference between the intensities of exhaustion of the plasticity of steels is discovered. Thus, the process of hardening of 15Kh13MF ferritic-martensitic steel is more intense, which is explained by the increase in nonparallelism and the decrease in the distance between subboundaries of the dislocation microstructure, reduction of sizes, and fragmentation of dislocation martensite. The 25Kh1M1F ferritic-pearlitic steel is characterized by less intense hardening explained by a different type of evolution of the dislocation structure connected with the transformation of dislocation nets and cells into globular and cellular disoriented structures and then into fragmented structures. It is shown that the relationship between the characteristics of substructural hardening, the density of dislocations within the low-angle boundaries, and the hardness (microhardness) of the material in the process of plastic deformation of heat-resistant steels can be described by a linear dependence independently of the level of strains. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 2, pp. 41–45, March–April, 2008.     

Effect of the W addition content on valence electron structure and properties of MoSi2-based solid solution alloys

Based on the empirical electron theory (EET) of solids and molecules, the valence electron structures (VES) of MoSi₂-based solid solution alloys have been analyzed using the average atom model. The results showed that with the increase of the W addition content, the hybridization steps of Mo and Si atom of the alloys occurred in C3 and 1, respectively. The hybridization step of W was always C5. The bond energy of the main bond branch, the covalence electron number on the strongest bond and the percentage of the total covalent electron numbers accounting for the total valence electron number of (Mo_1−x, W_x)Si₂ solid solutions increased with the increase of W addition content. These suggested that the addition of W would increase the melting point, hardness and strength and decrease the fracture toughness of (Mo_1−x, W_x)Si₂ solid solutions. Based on those results, MoSi₂-based solid solution alloys were manufactured, and the results of the experiments were in accordance with those of the theory.     

Phase stability,physical properties and strengthening mechanisms of concentrated solid solution alloys

We review recent research developments in a special class of multicomponent concentrated solid solution alloys (CSAs) – of which the recently discovered high entropy alloys (HEAs) are exemplars – that offer a new paradigm for the development of next generation structural materials. This review focuses on the role of inherent extreme chemical complexity on the phase stability, electronic, transport, and mechanical properties of this remarkable class of disordered solid solution alloys. Both experimental observations and theoretical models indicate that the phase stability of HEAs goes beyond the original conjecture that these alloys are stabilized by configurational/mixing entropy; rather, it results from competition between the homogeneously disordered phase and phase separation/intermetallic compound formation. Although the number of single-phase HEAs with equiatomic composition is limited, those that do exist often exhibit remarkable electronic, magnetic, transport, and mechanical properties. For the mechanical response, we discuss the solution strengthening mechanism which governs the strength and deformation behaviors of the CSAs, as well as the increasing evidence that low stacking fault energies (deformation twinning) plays an important role in the low temperature strength and ductility of CrMnFeCoNi related alloys. We also review the current understanding of the role of the number and type of alloy elements in determining the electronic, magnetic, and transport properties, in particular the dominant role of magnetic interactions in the properties of 3d-transition metal based alloys. Finally, we emphasize that, despite rapid progress in characterization and understanding of the phase stability and physical/mechanical responses of CSAs, there remain significant challenges to fully exploring the new paradigm that these alloys represent.     

Predicting the coating condition on ships using ICCP system data

The condition of coatings on the metallic surface of the hull of a vessel changes over its lifetime due to the action of the sea, deterioration of the paint itself, damage caused by impacts, etc. Although increased current demand from an impressed current cathodic protection (ICCP) system can indicate the presence of damage, the location and extent is unknown. The position, size and the seriousness of the damage are important issues from mainly two points of view.

• Corrosion: If the hull of the structure is corroded, the ship works inefficiently and can become dangerous from the crack initiation viewpoint.
• Noisiness of the vessel: As the damage proliferates along the hull structure, the current flux from the anode to the cathode also increases. This increases the noise of the vessel and makes it more detectable to an enemy from the defence point of view.

The goal of this work is to find a reliable method to discover the state of the coating of a vessel by using the commonly available data of its system of cathodic protection, ICCP. Copyright © 2004 John Wiley & Sons, Ltd.     

Characteristics of creep rate during the steady-state and accelerated stages criteria for evaluating damage to heat-resistant steels and alloys

Substantiation is provided for adopting strain characteristics as criteria of the damage content of heatresistant steels and alloys during high-temperature creep. The inadequacy of creep characteristics determined in laboratory tests of standard specimens in tension —analogous to characteristics obtained from primary creep curves constructed during service by measuring changes in the diameter of unmachined surfaces and steam pipes under internal pressure and variations in wall thickness —makes it necessary to adopt the latter as the sole criteria for evaluating damage content and predicting residual service life. Translated from Problemy Prochnosti, No. 12, pp. 31–36, December, 1994.     

Magnetic properties of solid and liquid AuFe alloys

The magnetic behaviour of dilute AuFe alloys up to 21 at%Fe was determined by susceptibility measurements between 300 and 1600 K. Judged by the experimentally derived effective magnetic moments and the paramagnetic Curie temperatures, the local environment around the iron atoms in the liquid state is obviously not very different from that in the solid state. The magnetic moments decrease with increasing solute concentration, and the interactions between the solute atoms are indicated to be negative in the dilute alloys and positive in the more concentrated alloys.     

Methodological aspects of creep prediction for heat-resistant steels and alloys. Part 1. Analysis of the equations of state

The validity of applying the complex of constitutive equations based on the concepts of the minimum commitment method and systems analysis of known experimental data to predict creep over a wide range of temperatures and stresses is discussed. __________ Translated from Problemy Prochnosti, No. 1, pp. 55–68, January–February, 2007.