Plastic deformation of single crystals of VSi2 and TaSi2 with the C40 structure

The deformation behavior of (0001)110 basal slip in single crystals of VSi₂ and TaSi₂ with the C40 structure has been investigated in the temperature range from room temperature to 1500 °C in compression. Plastic flow is observed only above 400 and 600 °C for VSi₂ and TaSi₂, respectively. The critical resolved shear stress (CRSS) for basal slip decreases with increasing temperature but exhibits a moderate peak around 1100 and 1400 °C for VSi₂ and TaSi₂ respectively. Dislocations with b = 1/3110 gliding on (0001) basal planes both in VSi₂ and in TaSi₂ are observed to dissociate into two identical partials with b = 1/6110 involving a stacking fault. High-resolution transmission electron microscopy of 1/3110 dislocations indicates that basal slip both in VSi₂ and in TaSi₂ occurs through a conventional single shearing mechanism, unlike in isostructural CrSi₂ and Mo(Si,Al)₂ in which basal slip occurs through a synchroshear mechanism.     

Plastic deformation behavior and operative slip systems of ZrSi2 single crystals with C49 type of structure

Plastic deformation behavior of ZrSi₂ single crystals with C49 type of structure was investigated at temperatures up to 1500 °C in comparison with other silicides with C11_b, C40 and C54 types of structures. [1 0 0](0 1 0), [0 0 1](0 1 0), [1 0 1](0 1 0), and [0 0 1](1 0 0) slip systems were determined to operate and their CRSSs monotonously decreased with increasing temperature.     

Influence of plastic deformation on the velocity and ultrasonic attenuation of copper single crystals

High-purity copper single crystal samples were plastically deformed between 0.02% and 1% in the direction. The absolute ultrasonic velocity and attenuation related to the dislocations in copper single crystal were measured as a function of the plastic deformation. The amplitude-independent Swing Model for dislocation resonance was considered to obtain information about the evolution of the dislocation density (Λ) with the degree of plastic deformation (%). The experimental data were interpreted as resulting from the contribution of two kinds of dislocations that lie in a cell structure. The results show a linear increase with the deformation of the density of dislocations (Λ_I) that lies in the cell walls [Λ_I (cm⁻²)≈1.5×10⁹ %]. The dislocation density inside the cell (Λ_II) is about two orders of magnitude lower than Λ_I.     

Anisotropic plastic deformation behavior of B2-ordered Fe_3Al single crystals at room temperature

The tensile plastic deformation behavior of B2-ordered Fe3Al single crystals at room temperature was systematically investigated. The results show that the mechanical properties are strongly orientation dependent. The plastic elongation of crystals with orientation near [110] is as high as 42%. Slip trace anal ysis shows that although slip planes are found to change among {110}, {11 2} and {123} with the change in orientations, the initial slip planes in a ll c ases are {110}. Five-stage work hardening curve including four linear stages and one parabolic stage is obtained; but not all stages are observed in the a ctual deformation of each crystal. In combination with investigations of disloca tion substructure, it is found that deformations in stage Ⅰ～Ⅲ are corresponding to the motion of two-fold superdislocations. The higher work hardening rate of stage Ⅱ is mainly due to the stronger interactions between primary dislocations and secondary dislocations than those in stage Ⅲ. Deformation in stage Ⅳ involved is not only the motion of two-fold superdislocations but also the slip of dissociated superpartials with APB traps and the formation of APB tube, both of which are attributed to the hardening. Deformation in stage Ⅴ is control led by the cross slip of dissociated superpartials. The dominated softening effect of cross slip reduces the hardening rate and leads to the formation of para bolic stage.     

Structure of single crystals of nickel high-temperature alloy after plastic deformation and heating

Methods of electron microscopy, x-ray diffraction analysis, and measurement of the microhardness are used to study the effect of moderate (under the conditions of creep) and intense (shear under pressure) deformation on the structure and hardness of single crystals 〈001〉 of a high-temperature alloy based on nickel. The special features of recrystallization and phase transformations in the alloy after deformation by different methods and heating are described. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 26 – 29, October, 2000. The material of the present paper has been reported at the Bern-shtein Perusal on 27 – 28 October 1999 at the Moscow Institute of Steel and Alloys.     

Ti3SiC2表面渗硅涂层的抗高温氧化性能

采用固体粉末包埋法在Ti3 SiC2 陶瓷上渗硅 ,研究了渗硅涂层的抗高温氧化性能 ,用XRD及SEM /EDS分析了渗硅涂层及其氧化后产物的成分、结构和形貌等。结果表明 :渗硅层主要由TiSi2 和SiC组成 ,在空气中氧化时形成了SiO2 和TiO2 的混合氧化物膜。渗硅样品在 110 0℃和 12 0 0℃下的恒温氧化速率比Ti3 SiC2 降低了 2～3个数量级 ,110 0℃下抗循环氧化性能也优于Ti3 SiC2 。但由于渗硅层中存在裂纹 ,循环过程中当裂纹贯穿整个渗硅层时 ,涂层的氧化速度开始增加 ,其保护作用逐步退化。在 110 0℃下空气中循环氧化时 ,经 40 0次循环后涂层已基本失效。     

Plastic deformation of single crystals of TiSi2

Compression experiments have been performed at high temperatures for single crystals of TiSi₂ with the C54 (oF24) structure. Compression axes chosen are -, b- and c-axes, and intermediate directions between a- and c-axes, and b- and c-axes. Based on the slip line observation and the geometrical consideration, it has been concluded that one of the three slip systems, (001)[110], ( 10)[130] and (0 1)[011], is activated depending on the compression axis; in the former two systems dislocations are assumed to be dissociated into superpartials, i.e. 1/2[1101→1/3[100]1+1/6[130] and 1/2[130]→3 × 1/6[130]. The (001)[110] slip is active at room temperature and the other two slip systems are active only above 1000 K. The thermal-activation analysis of the plastic deformation has shown that the deformation is controlled by the Peierls mechanism for the three slip systems; the total activation enthalpy is 1.5 eV for the (001)[110] slip and 4–5 eV for the ( 10)[130] and (0 1)[011] slips. An asymmetry of the Peierls potential is suggested for the (3 0)[130] slip.     

Effect of plastic deformation on the structure and properties of laminated composite materials

Experience with the development and application of plasma cutting of metals using reversed polarity current and mixed gas supply is described. The high efficiency of plasma cutting with reversed polarity in both the manual and automatic cutting modes in the plant conditions is stressed. It is noted that the number of activations of the constricted arc can be greater than 1000 without failure of the electrode.     

Effect of small perturbations on the evolution of polycrystalline structure during plastic deformation

The method of molecular dynamics has been used to study the influence of initial perturbations on the evolution of grain boundaries during the shear plastic deformation of a two-dimensional polycrystalline material with nanoscale grains. It has been shown that short-term thermalization-induced small perturbations result in noticeable differences in grain boundaries configurations at the deformation of 0.05 and the polycrystal completely loses its initial grain boundary structure at the deformation of 0.4.     

Effect of regimes of hot plastic deformation on the structure and properties of stamped billets

One way of increasing the service life and reliability of gas-turbine engines is to raise the endurance limit of compressor blades by improving the manufacturing technology. The endurance limit of the blades depends on many factors, the most important of which is the structural state of the material for blade billets. A stable, high endurance limit can be attained if the whole complex of technological effects, beginning with the hot deformation and ending with the surface treatment of ready parts, is optimized. The regimes of hot deformation which creates the initial structure mainly determines the endurance limit. In this paper the influence of the regimes of hot deformation on the structure and endurance limit of stamped billets imitating compressor blades is investigated for the KhN45MVTYuBR-ID (EP718-ID) alloy.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 27–29, January, 1995.     

Effect of severe plastic deformation and thermomechanical treatment on the structure and properties of titanium

The effect of different modes of combined treatment on the microstructure and mechanical properties of long-length semiproducts from commercial purity titanium is studied. The combined production process includes equal-channel angular pressing followed by thermomechanical treatment. Special features of formation of an ultrafine-grain structure in preforms and changes in mechanical properties are studied in different stages of the process. A comparative analysis of mechanical characteristics of titanium in the initial annealed state and after the combined treatment is performed. Scattering of mechanical properties over the length of preforms is studied.