Effect of spherically converging shock waves on phase and structural state of quenched Al-4 wt % Cu alloy

Optical metallography, scanning and transmission electron microscopy, and microhardness measurements have been used to perform a layer-by-layer study of the structure of a quenched Al-4 wt % Cu alloy subjected to loading by spherically converging shock waves. It has been established that, when using this mode of loading, the high-strain-rate plastic deformation of this alloy occurs via intragranular dislocation slip. No bands of localized deformation at the grain boundaries, twins, and adiabatic shear bands are formed. Highstrain-rate plastic deformation leads to the dissolution of Guinier-Preston zones.     

Deformation behavior of a niobium single crystal upon loading by spherically converging shock waves

Methods of X-ray diffraction, optical metallography, scanning and transmission electron microscopy, and microhardness measurements have been used for a layer-by-layer examination of the structure of a niobium single crystal after loading by spherically converging shock waves. It has been found that after loading the sample acquires a polycrystalline structure in the most part of its volume. It has been revealed that the basic mechanisms of high-strain-rate plastic deformation of the niobium single crystal are slip and the formation of a vortex structure through the development of deformation localization bands and the simultaneous formation and expansion of an internal cavity. The method of loading used in the study does not lead to the formation of adiabatic shear bands in niobium single crystals.     

Deformation behavior of copper upon loading by spherically converging shock waves: Low-intensity loading conditions

X-ray diffraction, optical metallography, transmission electron microscopy, and microhardness measurements were used to perform a layer-by-layer study of the structure of a copper sphere 70 mm in diameter after loading by spherically converging shock waves. It has been found that the high-rate plastic deformation of copper proceeds mostly by slipping, rather than twinning under the used loading conditions. Shear bands are observed at the macrolevel, while a homogeneous dislocation structure, microbands, and microtwins are observed at the microlevel.     

Effect of spherically converging shock waves on the phase and structural states of the artificially aged Al-4 wt % Cu alloy

Optical metallography, scanning and transmission electron microscopy, and microhardness measurements have been used to layer-by-layer study the structure of an artificially aged Al-4 wt % Cu alloy subjected to loading by spherically converging shock waves. It has been established that the high-strain-rate plastic deformation of this alloy, when using this mode of loading, occurs via intragrain dislocation slip and, in the middle and deep layers, also via the formation of localized-deformation bands at grain boundaries. The intragrain slip occurs inhomogeneously, by the formation of shear bands. The temperature distribution in various layers of the sample has been estimated.     

Structure and phase state of Zr-1% Nb and Zr-2.5% Nb alloys loaded by spherically converging shock waves

Four balls made of zirconium-niobium alloys are loaded by spherically converging shock waves of various intensities and then studied from layer to layer by X-ray diffraction, optical metallography, transmission electron microscopy, and microhardness measurements. The phase and structural states of the balls are found to depend on the loading conditions and the depth of layer location in a ball. The ω phase is retained in the near-surface layers of the balls only after low-intensity loading, and its content increases with the niobium content in an alloy. The high-rate plastic deformation of the balls, which have a fine-grained structure in the initial state, during loading under our experimental conditions is shown to occur via slip and the formation of adiabatic shear bands.     

Effect of spherically converging stress waves on the phase composition,structure, and physicochemical transformations of the mixture of aluminum and quartz powders

The phase composition and structure of a mixture of aluminum and quartz powders taken in a ratio of 1:1 have been studied after loading by spherical converging shock waves. A number of concentric layers (zones) have been observed in a meridian section of the sample after shock-wave loading. The pressures in the converging shock wave and in the diverging shock wave reflected from the center of the sample have been estimated as a function of the radial position of Lagrangian particles on the basis of the calculation of pressure profiles P(R, t). The data on the phase composition of different zones are considered in respect to the pressures induced by the converging and diverging shock waves at their boundaries. It has been established that pressures below ～45 GPa cause only additional compacting of the material and deformation of aluminum and quartz. In this case, the quartz grain size substantially decreases up to the transition into the X-ray amorphous state. The attainment of a pressure of ～45 GPa initiates the solid-state reaction of SiO₂ decomposition, which leads to the precipitation of pure silicon and the evolution of oxygen. The beginning of the silicon precipitation and the chemical reaction of Al₂O₃ formation are separated over the pressure scale. The critical pressure, which is necessary for the solid-state chemical reaction of the Al₂O₃ formation is about 50 GPa.     

Formation of martensite in austenitic steel upon loading by quasi-spherical converging shock waves

Methods of magnetic powder patterns (Bitter technique), optical microscopy, and transmission electron microscopy have been used to study the formation of martensite in a spherical sample of 12Kh18N10T steel upon loading by quasi-spherical converging shock waves. Prior to loading, the steel exhibited carbide banding (TiC and Cr₂₃C₆ carbides were located in bands along the axis of the initial sample). It has been shown that, upon loading, disperse crystals of martensite are formed in these carbide-containing bands. No martensite was formed in the central part of the solid sphere, in the surface layers, and in the Altshuler-pattern rays. It has been concluded that, in these regions, the temperature exceeded the M _d temperature, above which the deformation does not cause a martensitic transformation.     

Properties of high-purity iron

Conclusions It was found that high-purity iron with total O, N, C, S, and P equal to 6 at. ppm and total nonferrous impurities less than 6 at. ppm has an ultimate strength of 5 kg/mm² and yield strength of 2.1 kg/mm².Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 2–8, December, 1974.     

Notch toughness of high-purity iron

Conclusion Increasing the purity of iron by increasing the number of traverses in zone melting and the refining time in hydrogen lowers the ductile-brittle transition temperature.I. P. Bardin Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 15–16, March, 1976.     

Effect of deformation on magnetic aging of silicon iron

Conclusions Grain-oriented silicon iron with 3% Si, 0.007% C, and 0.003% N that is stretched during annealing has a high susceptibility to magnetic aging. The magnetic aging factor is determined by the heating time and the deformation of the strip in the process of annealing.Voronezh Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 56–58, October, 1974.     

Cross-rolling and annealing textures in high-purity iron

The deformation and annealing textures of cross-rolled high-purity iron specimens were determined by use of an X-ray Geiger counter spectrometer. The deformation texture was predominantly (100) [011], plus minor texture components of the (111) [1̄10] or the (111) [112̄] type. In a partially recrystallized specimen, the minor deformation texture components were replaced by new orientations, while the (100) [011] main deformation texture was retained. A rather complex and widely scattered texture was developed in the completely recrystallized specimen. This recrystallization texture could be derived from the deformation texture components by rotations around (110) poles. The difference in the tendency for recrystallization among different deformation texture components may serve as an important factor in the formation of annealing textures.     

变形速率对半固态AlSi7Mg合金变形性的影响

采用Gleeble 1 50 0热模拟机对半固态AlSi7Mg合金触变压缩过程中的变形性进行了研究。结果表明 ,当保温时间为 1 0～ 30s,变形温度为 579℃时 ,随着形变速率提高 ,试样内部最大抗力及最大应力皆呈上升趋势。应变率较小时 ,变形的主导机制由液相流动和阻尼液相流动渐变为颗粒滑动和颗粒塑性变形 ;应变率较大时 ,应力变化可分为三阶段 ,即瞬态激增段、平稳变化段及稳定变化段。瞬态激增段的变形机制由初始的液相流动和阻尼液相流动骤变为颗粒滑动和颗粒塑性变形 ,其它两个阶段为 4种变形机制交互作用。     

Effect of strain rate on deformation behavior of TRIP steels

Tensile deformation behavior of Si–Mn TRIP (TRansformation Induced Plasticity) steel with vanadium and without vanadium and the DP (Dual Phase) steel of the same composition were studied in a large range of strain rate (0.001–2000 s^?1) by routine material testing machine, rotation disk bar–bar tensile impact apparatus and high-speed material testing machine of servo-hydraulic type. In situ measurement of the transformation of retained austenite was performed by means of X-ray stress apparatus in order to have detailed knowledge about the transformation of retained austenite at quasi-static tensile. Microstructure of steels before and after tensile were observed by means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that there is no yield plateau observed on the stress–strain curve at quasi-static condition for TRIP steel containing vanadium because the vanadium carbide suppress the formation of Cottrell atmosphere in matrix. Retained austenite of Si–Mn TRIP steel containing vanadium transforms to martensite at loading stress of 502 MPa (its yielding strength is 486 MPa), while the transformation of retained austenite in matrix of Si–Mn TRIP steel without vanadium happens when its yielding process is finished at quasi-static tensile. It is confirmed that phase transformation of retained austenite in TRIP steel is strain induced phase transformation. It is noted that tensile elongation of TRIP steel at dynamic tensile is always lower than that at quasi-static tensile. That is because gradually strain induced phase transformation of retained austenite in TRIP steel is suppressed by deformation localization at dynamic tensile.     

NiTi形状记忆合金的热瞬态相变与变形行为研究

通过材料的热-力循环实验及数字图像相关(DIC)测量方法来系统研究Ni Ti记忆合金的热瞬态行为,得到不同恒应力水平下及不同温度变化率下的热瞬态响应。根据得到的实验结果,系统分析了温度诱发马氏体相变中的马氏体带演化出现的原因、演化规律以及临界相变应力与温度的关系,揭示了Ni Ti记忆合金的热瞬态相变及变形演化与所在的应力状态及温度变化速率的密切关系,为Ni Ti记忆合金的热瞬态过程的有限元多尺度模拟提供重要的参考。     

Effect of deformation temperature and strain rate on semi-solid deformation behavior of spray-formed Al-70 %Si alloys

Spray-formed Al-70%Si(mass fraction) alloys were deformed by compression in the semi-solid state.The effects of the deformation temperature, strain rate and the microstructure were studied. Two strain rates(1 s-1and 0.1 s-1) and six deformation temperatures (600 ℃, 720 ℃ , 780 ℃, 900 ℃, 1 000 ℃ and 1 100 ℃) were chosen. The stress-strain curve exhibits a peak at low strain and then decreases to a plateau before it starts to increase again as the strain increases. The stress required for deformation at lower strain rate and at higher deformation temperatures is less than those at higher strain rate and at lower deformation temperatures. Four mechanisms of semisolid deformation can be used to explain the different behaviors of the stress-strain curves under different conditions.     

Diffusion in high-purity iron: Influence of magnetic transformation on diffusion

Influence of magnetic transformation on volume diffusion, dislocation diffusion, and grain boundary diffusion in high-purity iron (Fe) has been studied. The intensity of the influence on volume diffusion is found to be proportional to the change of magnetization of the Fe matrix around the first and second shells of the diffusing atom. The influence of magnetic transformation on the grain boundary diffusion and dislocation diffusion in Fe is found to be much larger than that on the volume diffusion.