Influence of the reversible α–ε phase transition and preliminary shock compression on the spall strength of armco iron

Full wave profiles are used to determine the Hugoniot elastic limit and the spall strength of armco iron samples with an as-received structure and the samples recovered after preliminary loading by plane shock waves with an amplitude of 8, 17, and 35 GPa. The measurements are performed at a shock compression pressure below and above the polymorphic a–e transition pressure. Metallographic analysis of the structure of armco iron shows that a developed twinned structure forms inside grains in the samples subjected to preliminary compression and recovered and that the twin concentration and size increase with the shock compression pressure. The spall strength of armco iron under shock loading below the phase transition pressure increases by approximately 10% due to its preliminary deformation twinning at the maximum shock compression pressure. The spallation of samples with various structures at a shock compression pressure above the phase transition proceeds at almost the same tensile stresses. The polymorphic transition in armco iron weakly affects its strength characteristics.     

Neutron diffraction study of the interaction of iron with amorphous fullerite

The amorphous fullerite C₆₀ has been prepared by mechanical activation (grinding in a ball mill), and its interaction with iron during sintering of powders with 0–95 at % Fe has been studied. After sintering in the range 800–1200°C under a pressure of 70 MPa, the samples have nonequilibrium structures different from the structures of both annealed and quenched steels. In this case, the carbon phase, i.e., amorphous fullerite, undergoes a polyamorphous transition to amorphous graphite. It has also been shown that the interaction of amorphous fullerite with iron is weaker compared to crystalline fullerite or crystalline graphite.     

国产纯铁的轧制与再结晶织构

用极固与金相研究工业纯铁的轧制与再结晶织构和组织。热轧后的试样经过两种冷轧方法：(1)压下率为98.8%,与(2)压下率为64.5%,中间700℃熟炼;二次冷轧和压下率63.5%。试样在氢气中分别于(a)650°和(b)1000℃熟炼。第一类材料的轧制织构经测定为(100)[011]+(112)[110]+(111)[112].试样在a与γ区域熟炼后的主要取向为(100)[011]和(111)[112]。第二类材料的轧制织构与第一类相似,惟偏离角度较大。表面与内部织构不同。第二类材料熟炼后的再结晶织构基本上相似,金相组织显出第二次再结晶现象。     

Microhardness of armco iron samples with different initial structures after rolling in a helium or nitrogen medium

We have analyzed the dependences of microhardness H on load P for the surface layers of Armco iron samples with different initial structures, i.e., annealed and after equal-channel angular pressing (ECAP). The microhardness was measured in air after rolling of the sample in helium or nitrogen medium. It has been found that these mediums produce different effects on the H(P) dependences for preliminarily annealed samples compared to those subjected to ECAP. This is due to the differences in their initial defects structures and in the types of binding forces of helium atoms and nitrogen molecules with dislocations, which determine the intensity of their penetration into the surface layer of the samples under investigation. We have obtained curves that describe the release of helium from samples rolled in different mediums and have measured the amount of helium.

     

Evolution of the phase-structure state during annealing of Fe-ZrN films grown by magnetron sputtering

The evolution of the phase-structure state of Fe-ZrN films grown by RF magnetron sputtering and annealed at T = 200–650°C has been studied by transmission electron microscopy, high-resolution electron microscopy, and X-ray diffraction analysis. It has been found that the initial state of the film contains 1- to 5-nm crystallites of α-Fe-based solid solution supersaturated with nitrogen. The number of such crystallites increases, the concentration of nitrogen in them decreases and 2- to 10-nm nanocrystallites of ZrN and Fe2N nitride phases appear after annealing. The formation of zirconium nitride at the first stage (200–500°C) is associated with a decrease in the degree of supersaturation of the α-Fe lattice with nitrogen. At a higher annealing temperature (650°C), a decrease in the nitrogen concentration in the lattices of both the bcc Fe and zirconium nitride phase leads to the formation of iron nitride crystallites.     

Amorphization of armco iron by boron implantation and subsequent crystallization by heat treatment: A CEMS,X-ray and ultramicrohardness study

The phase compositon of the near-surface zone of armco iron implanted with B⁺ ions (100 keV) at 200 °C was analyzed by CEMS and X-ray diffraction. The existing phases (bcc iron, Fe₂B and an amorphous Fe-B phase) were subsequently modified by heat treatment at various temperatures. The influence of the phase modifications upon the mechanical properties was studied by ultramicohardness measurements.     

Study of plastic deformation and proton irradiation influence on phase transitions in C18N9T stainless steel

Transmission and post-nuclear-reaction emission Mössbauer spectroscopy was used for investigation of radiation effects and plastic deformation influence on C18N9T steel. The rolled foil was annealed in 10^?6 Torr vacuum at 870 K during 2 hours and was irradiated by 30 MeV protons at current density of 0.8μ A up to doses of 5×10¹⁷ cm^?2 on the isochronous cyclotron at the liquid nitrogen cooling of the target. The Mössbauer spectra obtained before and after the sample irradiation in transmission geometry are identical. The emission spectrum is analogous to the spectrum of the plastically deformed sample. It is concluded that during irradiation in the steel the processes take place which are similar to those at plastic deformation and connected with redistribution of the alloy component atoms.     

考虑底充胶固化过程的InSb面阵探测器结构分析模型

液氮冲击中In Sb面阵探测器的易碎裂特性制约着探测器的成品率,建立适用于面阵探测器全工艺流程的结构模型是分析、优化探测器结构的有效手段.本文提出了用底充胶体积收缩率来描述底充胶在恒温固化中的体积收缩现象,同时忽略固化中底充胶弹性模量的变化来建立底充胶固化模型,给出了底充胶在恒温固化中生成的热应力/应变上限值.借鉴前期提出的等效建模思路,结合底充胶固化后的自然冷却过程和随后的液氮冲击实验,建立了适用于In Sb面阵探测器全工艺流程的结构分析模型.探测器历经底充胶固化、自然冷却至室温后的模拟结果与室温下拍摄的探测器形变分布照片高度符合.随后模拟液氮冲击实验,得到面阵探测器中累积的热应力/应变随温度的演变规律,热应力/应变值极值出现的温度区间与液氮冲击实验结果相符合.这表明所建模型适用于预测不同工艺阶段中面阵探测器的形变分布及演变规律.     

Mechanical tests of the conduit tubes of a conductor for the Toroidal winding of the International Thermonuclear Experimental Reactor (ITER)

Extremely stringent requirements, which include the impact toughness at the liquid-helium temperature, are imposed on the material of the conduit tubes for International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) conductors. Modified 316LN-IG stainless steel is recommended as the conduit tube material. Steel 316LN-IG tube samples (both full-size samples and sub-sized samples) are subjected to mechanical tests at various stages of the process of conductor production: in the as-recieved state and after compacting, preliminary elongation by 2.5% at room temperature, and annealing at 650°C for 200 h in a pure helium gas atmosphere. The tests are carried out at room, liquid nitrogen, and liquid helium temperatures and satisfy the standards of the American Society of Mechanical Engineers (ASME and ASTM). The results of sub-size and full-size samples testing show that the last one gives more representative results to qualify the weld joints in liquid nitrogen. When the temperature decreases or the strain increases, the magnetization of the samples increases, especially in the weld area. Strain measurements with an extensometer demonstrate that the intracrystal processes occurring at the liquid-helium temperature can lead to a significant change in the local load, up to complete unloading in a deformation zone. Unusual local serrated deformation is observed with an extensometer installed in the weld area during tests in liquid helium: this deformation is the result of compressive jumps opposite to the loading direction.     

液氮冲击中锑化铟焦平面探测器形变研究

液氮冲击中锑化铟红外焦平面探测器(InSb IRFPAs)的形变研究对理解探测器结构设计可靠性、预测探测器耐冲击寿命具有重要意义.在系统分析液氮冲击结束时模拟得到的InSb IRFPAs形变分布与方向的基础上,提出了降温过程中累积热应变完全弛豫的设想,升至室温后的模拟结果重现了室温下拍摄的InSb IRFPAs典型形变分布特征.经分析认为室温下拍摄的InSb IRFPAs表面屈曲变形源于底充胶固化中引入的残余应力应变,变形幅度随降温过程逐步减弱,至77 K时完全消失,升温过程则依据弹性变形规律复现典型棋盘格屈曲模式.这为后续InSb IRFPAs结构设计、优化及耐冲击寿命预测提供了理论分析基础.     

EPR Study of Iron Ion Complexes in Human Blood

Electronic states of iron ion complexes in human blood from patients with melanoma have been investigated by electron paramagnetic resonance (EPR). The measurements were performed at liquid nitrogen temperature (77 K) on an X-band EPR spectrometer. Numerous types of iron paramagnetic centers have been identified. In several kinds of protein complexes exemplified by methemoglobin, transferrin or ferritin, various forms of trivalent iron have been found. Three groups of patients with typical EPR spectra have been individualized. These groups differed in types and concentration of paramagnetic centers in peripheral blood. A good correlation has been found between the EPR results, the total iron ion complexes concentration and transferrin saturation.     

Effect of thermal annealing on nitrogen implanted epitaxial Fe films

Nitridated iron is a promising material for potential applications in permanent magnets. Recent work on stabilization of nitridated iron in a foil form through nitrogen ion implantation and annealing motivates to study effect of thermal annealing on the surface of nitrogen-implanted iron. In this work, we show effect of annealing on chemical state and magnetism of nitrogen implanted epitaxial iron films. It is observed that nitrogen in the lattices only stays at the lower temperatures than 450 °C. In addition, significant reduction and lattice modification are taken placed, when the film is annealed at 450 °C. The increases of saturation magnetization and coercivity, where it is annealed at 450 °C, are likely to be triggered by reduction of oxygen contents at the surface and thinning of Fe₂O₃.     

Magnetic Properties of Iron/Graphite Core-shell Structured Nanoparticles Prepared by Annealing of Fe-C-N Nanocomposite

We are reporting the core-shell structured iron/graphite nanoparticles formed during annealing of a nanopowder prepared by laser pyrolysis of gas phase reactants. The originally synthesized Fe-C-N nanocomposite powder has been characterized by TEM, XRD and magnetic measurements. Nanopowder was heated up to 800 °C at ～ 1 Pa vacuum. Presence of iron nanoparticles with mean diameter 40 nm in the annealed state of nanopowder was proved by XRD and TEM analyses. Mössbauer spectroscopy was used for characterization of synthesized/annealed nanopowder to confirm the qualitative change in phase composition.     

Mössbauer study of braunite

Braunite mineral from Triodi manganese deposits (India) has been studied by Mössbauer spectroscopy. Room temperature Mössbauer spectra show a well resolved quadrupole splitting which is attributed to the substitution of iron in Mn (2) site. Emergence of another doublet at liquid nitrogen temperature has been attributed to the location of small quantities of iron in Mn (4) site. Iron is in Fe III and high spin state. At 4.2 K the internal magnetic field is 415 kOe.     

Morphology of nanostructures formed on the van der Waals surface of GaSe layered crystals annealed in sulfur vapor

The morphology of nanostructures, which were grown on the (0001) van der Waals surface of layered GaSe crystals and annealed under thermodynamically equilibrium conditions at high pressures of sulfur vapor, has been investigated using atomic force microscopy. The morphology and phase composition of the nanostructures are determined by the deformation and chemical interactions between the vapor phase and the crystal surface and by the thermodynamic conditions of annealing. Elements of nanostructures are formed as small Ga₂S₃ nanocrystallites, pyramidal quantum dots, and quantum rings on the defective (0001) van der Waals surface that contains nanosized indentations (nanocavities) and liquid gallium.     

退火对Ga_2O_3薄膜特性的影响

采用金属有机物化学气相沉积法在c面蓝宝石衬底上生长了高质量的β-Ga_2O_3薄膜,并将样品分别在真空、氧气、氮气氛围下退火30 min,研究了各类退火工艺对Ga_2O_3薄膜特性的影响,对退火所得的薄膜进行了X射线衍射、光致发光谱、紫外透射谱和原子力显微镜扫描的研究。结果表明,各类退火工艺均能够优化薄膜的晶体质量和表面形貌,同时有效改善了薄膜的光学性质。其中,氧气退火后的样品在可见光波段透射率高达83%,且吸收边更加陡峭;表面粗糙度降至0.564 nm,其表面更为平整。这些结果说明氧气退火对晶体质量的提高最为显著。氮气、真空退火的样品在光致发光谱中出现365 nm的发光峰,这是大量氧空位的存在导致的。     

Crystallization behavior of iron-based amorphous nanoparticles prepared sonochemically

In general, a rapid quenching is required to obtain an amorphous metal. It is known that an intensive ultrasonication generates a very high temperature within cavitation bubbles in a very short moment, which enables a rapid quenching process in a liquid phase synthesis. In this study, the sonochemically-derived “amorphous iron” from Fe(CO)₅ was carefully examined by XRD, TEM, TG-DTA. The product was found to be an amorphous containing a certain amount (∼15%) of volatile component that can be removed by heating in a nitrogen flow. After annealed in the inert atmosphere at 600 °C, cooled down to room temperature, and then exposed in air (oxygen), the sample showed a strong exotherm accompanied by a weight gain. This is due to oxidation of fine metallic iron. Experimental operations of such a reactive material were examined.     

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

Physics of the Solid State - The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T...     

Jumplike microdeformation of nanostructured metals

The parameters of microdeformation jumps for copper, aluminum, titanium, and Armco iron with the initial (annealed) structure and after equal-channel angular pressing are investigated in a creep mode under low compressive stresses. The strain rate is measured with a laser interferometer in 0.15-μm linear displacements. It is demonstrated that the values of the microstrain rate and the mean sizes of jumps for the annealed metals are larger than those for the metals subjected to severe deformation. It is revealed that there is a correlation between the jumps of microplastic deformation and the size of nanometal grains. The inference is made that, for nanostructured metals, as for other materials, the structural heterogeneity is one of the factors responsible for the jumplike deformation.