STM Study on the Surface Relief and Mechanism of Bainite Transformation

Scanning tunneling microscopy (STM ) has been first employed to study the surface relief accompanying bainite transformation in a Fe-2.17C-12.18Cr-0.31Si-0.26Mn (wt pct) steel. With the exclusive vertical resolution of STM, we observed that the surface relief associated with bainite is a group of surface reliefs related to subplates, subunits and sub-subunits. As a whole, the relief group is in a tent shape, not of invariant plane strain (IPS) type, which is obviously different from that of martensite, and implying that bainite is not formed by shear mechanism. The fine structure of bainite in Fe-1.0C-4Cr-2.0Si (wt pct) alloy has also been studied with STM and TEM. It is found that the bainite plate is composed of subplates, subunits and sub-subunits. On the basis of the fine structure inside a bainitic ferrite plate observed under STM, a sympathetic-ledgewise mechanism of bainite formation is proposed     

Three Dimensional Morphology and Microstructural Evolution of Bainite in Steels

The 3-D morphology of bainite in steels has been studied by SEM with high resolution. Based on the dual-surface observation results, the bainite is divided into three sub-categories:upper,transient and lower bainites. The subplates composing upper bainite sheaf are lath-like while the whole morphology of lower bainite and that of its subplates are plate-shaped. The subunits in lower bainite seem to be lumpish. The 3-D morphology of transient bainite proves to resemble both upper and lower bainites on some aspects. The microStructural evolution of three types of bainite has been discussed.     

Formation of PFZ and Its Effect in a RSP AI-Li Alloy

The formation of precipitation free zone (PFZ) and its effect in a RSP AI-Li alloy has been studied.The results show that PFZ is easy to form when aged at 190℃,but there is no equilibrium phase ongrain boundaries.The growth of PFZ in the alloy is different from that in conventional AI-Li alloys,The effect of PFZ is of great importance because of its large volume fraction in the alloy.It offsets thebeneficial effect of RSP,and is thought to be an important factor that leads to the poor toughnessand low ductility of RSP AI-Li alloy sheet.     

Study on the Diffraction Patterns of α"-Fe_(16)N_2 with Jack-1 and Jack-2 Structural Parameters

To whom correspondence should be addressedE-mail: zhiquanliu@yahoo. com1. IntroductionIn the early 1950s, Ja.k[1] investigated the FeN binary system systematically, and discovered a"Fel6Nz as a new ordered nitride with a bet structure.In 1972, Kim and Takaha.hi[2] reported that the FeN films evaporated in an NZ atmosphere, which resulted in a polycrystalline mixture of or--Fe and crl'FeleNz, had an ultrahigh saturation magnetization.Since then, much attelltion has been paid to thestudy o…     

Formation of Omega-like Nanocrystalline in the Melt-Spun Nd_(85)Al_(15) Alloy by Phase Transformation

Microstructure and subsequent phase transformations on heating of the melt-spun Nd85Al15 alloy have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The melt-spun Nd85Al15 alloy shows two-stage transformation processes as follows: amorphous+72 nm supersaturated bcc-Nd(AI) solid solution-7 nm omega-like phase-AlNd3+hexagonal Nd. The activation energies for the first and second transformation were found to be 100 kJ/mol and 188 kJ/mol, respectively. The formation mechanism of nanoscale omega-like phase is discussed.     

Energy Minigaps in the Quantum Well Wires with Periodical Lateral Surface Structures

Energy minigaps caused by lateral surface structures in quasi-one-dimensional GaAs/ AlAs quantum well wires are calculated with the variational and degenerate-perturbational approaches.By a coordinate transformotion. the structured interfaces of the wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of the energy minigaps on the lateral surface structures are discussed.     

A Crystallography Study of Bainitic Transformation in a Cu-Zn-Al Alloy

The crystallographic nature of initialisothermal phase transformation in Cu-26Zn-4Al(wt-％) was investigated. The kinetic transforma-tion curve, morphology, crystal structure,substructure, orientation relationship and twinrelationship of bainite plates have been studiedby means of optical and transmission electronmicroscopy. The experimental results showedthat the characteristics of initial 8→bainitetransformation are not exactly consistent withthat found in martensite transformation, forexample, orientation relationship between matrixand bainite does not exist in martensitetransformation.     

Finding of Gray Points on the Surface of the Sn-Fe Alloy Layer and Its Effects on the Corrosion Resistance of the Alloy Layer

After removing tin coating of tinplates offered by some steel works, we discovered massive, highly disperse gray points outspreading along rolling direction on the surface of the alloy layer. Morphology of the alloy layer was observed by scanning electron microscope (SEM), and many cavities of the alloy layer were found out in the gray point. After analyzing the composition of the alloy layer, we found that content of Fe in the gray points was more than that in the normal alloy layer. Moreover, corrosion resistance of the alloy layer declines with increase of amount of gray points. In addition, the hot-humidity testing was carried out for some plates whose surface has many gray points. After 14 days, there were many rust points occurring in the edge of gray points and in the small gray points. The morphology of rust points was observed by atomic force microscope (AFM). The reason why rust points generated in the edge of gray points and in the small gray points was discussed.     

Kinetics of α-FeO(OH)Formation in Weak Acidic Medium

The kinetics of α-FeO(OH) formation in weakacidic medium was studied.The effects of the initialconcentration,temperature,pH value,partial pres-sure of oxygen,air flow rate and agitating intensityon the oxidation rate of Fe(OH)_2 suspensions havebeen investigated.It is confirmed that the reactionorder for Fe(Ⅱ) is zero at the stage of α-FeO(OH)seeds formation,and about 0.5 at the stage of theseeds growth,and in the whole process partial pres-sure of oxygen appears in first order.The activationenergy is determined.The dissolution-oxidationequilibrium which exists in the process of seedsformation has been suggested,by which the zeroorder reaction for Fe(Ⅱ) and the plateau in thepH-t curve were explained.Physical process is therate-determining step of the heterogeneousreaction.The study on the kinetics of α-FeO(OH)formation may provide some fundamental informa-tion for the reactor design,the engineering amplifi-cation and the optimization control in the industrialprocess.     

Cleaning of the Surface of Silicon Structures in the Technology of Very Large‐Scale Integrated Circuits with the Use of Rapid Heat Treatment

Results of investigation of the quality of cleaning of the surfaces of silicon, silicon dioxide, and aluminum films with the use of rapid heat treatment prior to the application of a photoresist and the influence of such cleaning on the deviation of the linear dimensions of a topological pattern subjected to etching are presented. All the results are considered in comparison to the traditional methods of surface cleaning. The parameters of the elements of very largescale integrated circuits manufactured with the use of rapid heat treatment for cleaning of the surfaces of various thinfilm materials coated on silicon are presented.     

Formation of a thin film containing α-carbine in the magnetron sputtering of graphite targets and the impact of an external photoactivation source

The possibility of formation of a thin film containing α-carbine in magnetron sputtering of graphite targets and the impact of an external photoactivation source with the spectral density of the radiation flux ～5 × 10⁸ W/m³ at the wavelength of 300 nm and at the substrate temperature ～660 K is shown experimentally.     

Glass Formation and Thermal Stability in Rapidly Solidified Al-Fe-V-Si Alloy with Misch Metal Additions

A new amorphous Al87.3Fe4.3V0.7Si1.7Mm6.0(Mm: misch metal) was prepared by using melt-spinning technique. Differential scanning calorimetry (DSC), X-ray diffraction (XRD). transmis-sion electron microscopy (TEM) and energy dispersive X-ray (EDX) have been used to investigatethe crystallization behaviour of thi5 amorphous alloy It is found that the crystallization processcan be concluded as follows: amorphous→ amorphous plus fcc-Al→ fcc-Al plus AI11(La,Ce)3plus i-phase (icosahedral)→ fcc-Al plus Al11(La,Ce)3 plus i-phase plus ic-phase (icosahedralcompounds). The results of microhardness measurement show that HV values are higher thanthose in Al-Fe-V-Si based alloy and the maximum HV value corresponds to the coexisting ofnanoscale Al particles and i-phase.     

Structure and interactions of calcite spherulites with α-chitin in the brown shrimp (Penaeus aztecus) shell

White spots form in the brown shrimp (Penaeus aztecus, Decapoda) shell during frozen storage. The mineral formed consists of calcite incorporated into an amorphous α-chitin matrix. We studied mechanisms of interaction of amorphous α-chitin macromolecules with hkl crystal planes to form highly ordered structures, as well as the role of specific sites in the biopolymer, which can be related to nucleation and spheroidal crystal growth. We used low vacuum scanning electron microscopy (LVSEM), X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), and molecular mechanics modeling (MM+ method). AFM images showed fingerprint distances in the biopolymer and a highly layered structure in the crystalline material. The presence of α-chitin, with a specific spatial distribution of radicals, is thought to be responsible for nucleation and to thermodynamically stabilize ions to form the spherulite crystalline phase, which are usually oval to spherical (0.10 to 200 μm in diameter). Our models of crystal–biopolymer interaction found high affinity of CO₃²⁻ anions in the (104) crystalline plane (the main plane in calcite monocrystals) to NH– groups of the biopolymer, as well as of the CO in the biopolymer to Ca²⁺ cations in the crystalline structure. These interactions explain the spherical growth and inhibition in some planes. The specific physicochemical interactions (docking of groups depending on their geometrical distribution) suggest that the biomineral structure is controlled by the biopolymer on a local scale. This information is useful for further design and improvement of (hybrid) materials for versatile application, from nanotechnology to biomedicine and engineering.     

Heat Transfer from a Surface with Spherical Hollows in Boiling of Water and a Steam‐Water Mixture in the Supercritical Region

The authors carried out an experimental investigation of heat transfer in the supercritical zone in flow of water and a steamwater mixture in a vertical annular channel. The interior wall heated by the current was either smooth or with hollows stamped in a straightline order. The application of them increased the heattransfer coefficient by a factor of 1.5–2 and more. The increase in the frictional resistance was much smaller.     

How Hydrogen Affects the Formation and Evolution of Persistent Slip Bands in High-Purity α-Iron

The effect of hydrogen on the fatigue behavior of materials has been studied extensively during the past 100 years, but is just poorly understood due to the complex interplay between hydrogen and deformation processes. In this context, hydrogen damage of metals is becoming one of the major challenges of decarbonization. While most work focuses on f.c.c. materials, the availability of relevant results becomes sparse when considering technologically highly relevant b.c.c. metals such as structural steels. This work uses in situ electrochemical hydrogen charging of α-iron steels to investigate the formation and evolution of intrusions and extrusions prior to fatigue crack initiation using a new charging setup by which the specimens are charged from the interior. The advantage of this innovative technique is that the surface of the specimens can subsequently be characterized using atomic force microscopy without artefacts from electrochemical charging or corrosion. Hydrogen is shown to enhance slip localization at the early stages of damage. The developed persistent slip lines are less pronounced. By means of transmission Kikuchi diffraction, it is shown that orientation gradients between cells in the dislocation structure are much weaker in the presence of hydrogen. Hence, hydrogen appears to promote slip reversibility in b.c.c. materials.     

X-ray Diffraction Line Profile Broadening of Fe_(50)Pd_(50) Alloy Ultrafine Particles

The composition distribution in Fe50Pd50 alloy ultrafine particles prepared by inert gas condensation method was investigated in details by means of X-ray diffraction technique through deconvolution of the X-ray diffraction data. The microscopic composition distribution in the alloy UFP was identified, which is caused by nonuniformity of the melt, fractional distillation during the evaporation process and statistical fluctuation during nucleation and coalescence of the alloy particles. The composition distribution affects the properties of the alloy UFP     

Surface Layer of Ni_(68)P_(18)Cr_(14) Amorphous Alloy

In Ni_(68)P_(18)Cr_(14) amorphous alloy, the dominant component elements Ni and P were in lower contentin the surface layer, while Cr was enriched. There was a P enrichment region just below the surfaceoxide layer, which was supposed to enhance the surface segregation of Cr. Nickel was less oxidizedthan Cr.