Showing papers by "University of Science and Technology Beijing published in 1990"

A new diagnosis theory with two kinds of quality

Abstract: The Shewhart chart can show the indication of abnormality, but it cannot tell us where and what the abnormality is, that is it is not diagnostic. The diagnosis with two kinds of quality is a new diagnosis theory. According to previous studies, at any operation there are always two kinds of quality as follows: (1) total quality—just the quality in the usual sense, (2) specific quality—the quality specifically resulting from the current operation itself, not including the influence of the preceding operation. Thus, correspondingly, there are: (1) two kinds of control chart, that is the Shewhart chart for total quality and the cause-selecting chart for specific quality; (2) two kinds of process capability index, that is the total process capability index (just the one in the usual sense) for total quality and the specific process capability index for the specific quality. In fact, the total quality and the specific quality reflect, respectively, the real and the ideal state of quality of the current operatio...

On the microstructure of graphite spherulites in cast irons by TEM and HREM

Abstract: The microstructure of graphite spherulites (G.S.) in nodular cast irons doped with either Ce or (Mg + Ce) has been extensively studied using transmission electron microscopy (TEM), μ-diffraction and lattice images techniques. The results show that the section of a well-developed G.S. consists of fan-like areas formed from platelets with sizes ranging from several to tens nm radial and hundreds nm circumferential. The [001] direction of the graphite platelets within each fan-like area tends to parallel to the radius of the G.S. but spreads about ± 10° among them. 002 Lattice images of graphite reveal the arrangement of graphite based plane layers, such as branching, bending and stages with intercalary layers besides dislocations and faults. These structural characteristics of G.S. have shown that {001} planes of graphite did grow predominatly through the formation of stages by intercalary layers of ceriumoxide and ceriumoxysulfide, then the G.S. takes its final morphology.

Quasicrystals in rapidly solidified alloys of AlPt group metals-III. Quasicrystals in rapidly solidified AlRh and AlIr alloys

Abstract: Decagonal quasicrystals were found in both rapidly solidified Al5Rh and Al5Ir alloys with a periodicity of about 1.6 nm along the tenfold axis. Apart from the already known intermetallic phases Al9Rh2 and Al9Ir2, two new hexagonal AlIr phases have been found. One is metastable and isostructural with the hexagonal α-AlFeSi, consisting of many icosahedral subunits in its structure and the other has lattice parameters a ≈ 0.31 nm and c ≈ 0.52 nm.

The texture of Ti-51.5 at.% Ni rolling plate and its effect on the all-around shape memory effect

Abstract: The All-Round Shape Memory Effect (ARSME) of both specimens cut out from a rolling plate of Ti-51.5 at.% Ni alloy along respectively the rolling direction and that perpendicular to the rolling direction has been investigated. The results indicates that the ARSMEs of these two specimens are very different. This large difference is due to the texture structure of Ti-51.5 at.% Ni rolling plate. The longterm-anneal at high temperature 820°C can change the texture a little, which results in a decrease of the ARSME. The mechanism of the difference of ARSME caused by the texture has been clarified.

Two types of boron segregation at austenite grain boundaries and their mutual relation

Abstract: The distribution of boron in 10 p.p.m. B-doped Fe-30 wt% Ni austenitic alloy was investigated by means of particle tracking autoradiography (PTA). It was shown that when quenched from a certain temperature between 750° C and 1220° C with medium cooling rates, both equilibrium and non-equilibrium grain boundary segregation of boron appeared in the alloy. The degree of segregation represented the sum of the two kinds of segregation of boron. A transition temperature, of approximately 950° C, was found below which the equilibrium grain-boundary segregation was dominant and above which the non-equilibrium grainboundary segregation was dominant. For the degree of segregation achieved by these two types of segregation of boron there exists a temperature from 1000° C to 1050° C at which a minimum amount of segregation is obtained. It was also shown that non-equilibrium segregation of boron can considerably promote the precipitation of boride at grain boundaries.

Theoretical investigation on the inverse black body radiation problem

Abstract: After reviewing previous work on the inverse black body radiation problem, a completely new approach to solve the problem not only theoretically but also numerically is presented. The first exact and concise expression for the solution is shown in this work based on the Fourier transform theory. Its existence, uniqueness, and stability are discussed in detail. The problem of convergence has been completely eliminated. >

Equilibria between cerium or neodymium and oxygen in molten iron

Abstract: Autoradiographs show that there is an obvious reaction between Ce and Nd in liquid iron and the MgO/CaO crucible wall. For reaching the Ce-O, Nd-O equilibrium, a long melting period and the addition of rare earth elements (RE’s) in several batches were needed to ensure the full reaction between the RE’s in the melt and crucible wall. The dissolved Ce or Nd content in iron was measured by means of radioactive isotopes141Ce or147Nd and electrolysis in the organic electrolyte. The oxygen activity was measured by solid electrolyte sensors made of ZrO2(MgO) tube. The relationships between the equilibrium constants and the temperatures for reactions Ce2O3 (s) = 2[Ce] + 3[O], CeO2 (s) = [Ce] + 2[O], and Nd2O3 (s) = 2[Nd] + 3[O], as well as the corresponding thermodynamic parameters, have been determined.

The computer algorithm and program for the generation of phase stability diagrams

Abstract: The stability area of substance in the phase stability diagrams is defined by the solution of a set of linear inequalities and its geometrical shape is a convex polygon. A new computer algorithm for the generation of the phase stability diagrams have been proposed in this paper, in which a series of relevant objective functions with minimum numbers were introduced to the set of linear inequalities to form the problems of linear programming. The FORTRAN program has been constructed to produce the phase stability diagrams by the use of the Revised Simplex Method that is used to solve the problems of linear programming. Several examples of its applications are presented. Since the set of linear inequalities that defines the stability area of substance has been solved mathematically in this method, it is considerably simpler and more reliable than previously reported method. Also it is very convenient for the more complex systems.

Influence of non-geometric effect of PSB on crack initiation in aluminium single crystal

Abstract: We present an investigation of the crack initiation by cyclic deformation on the two special surfaces of pure aluminium single crystal. One is the side-surface containing the active Burgers vector, the other is the top-surface forming the smallest angle with the active Burgers vector. The fatigue test is performed at the constant resolved shear stress amplitude (5 MPa), zero mean stress. Experimental results show that many microcracks are initiated on the side-surface on which no PSB surface topographies are formed during cyclic deformation. Cracks on the side-surface are short with mean length of about 10 μm and distributed approximately in a similar direction, perpendicular to the active Burgers vector, whereas on the top-surface cracks, similar to those reported before, are not as obvious as those on the side-surface. Observations by scanning acoustic microscopy show that the fatigue damage on the side-surface is much deeper than that on the top-surface. A model of crack nucleation by voiding is suggested.

The Acceleration Mechanism of Stress on Anodic Dissolution of Bare Metal Surface

Abstract: The difference in energy between the atoms in dislocations and those in a dislocation-free lattice is analyzed. The analysis suggests that the electromotive force of atoms in dislocations is 2.1 V higher than that of the atoms in dislocation-free lattices, and the anodic dissolution rate of atoms in dislocations is 1017 times that of the atoms in dislocation-free lattices. A model of the anodic dissolution of bare metal surface has been proposed. The theoretical equation proposed according to the model is i = i0 exp [flnF(q~a - ~e)/RT] �9 exp [flnFV/RT]. p. qJ  10 -15 The relationship between the increase of current density of anodic dissolution of bare metal surface and the increase of dislocation density has been calculated by this equation. The theoretical calculation shows that the current density rises slowly with dislocation density when the dislocation density is below 101~ . However, above 101~ , it increases greatly. The effect of the stress-strain on the current density of anodic dissolution of a bare single-crystal surface of 321 stainless steel in 3.5 pct MgC12 solution has been measured by a rapid scratching and recording device designed by the authors. The experimental results show that the effect of stress-strain on the current density of anodic dissolution of a bare singlecrystal surface is small in the range of elastic deformation; however, it is marked in the range of plastic deformation. The experimental results are consistent with the theoretical calculation. Several research workers 11'2m have shown that the electrode potential decreases and the anodic current rises as the metals are stressed or strained. Despic et al. [3] studied the effect of strain on anodic dissolution kinetics of several metals. It has been found in the case of iron in acid solutions that the overall effect of elastic strain is small and the effect of yielding on the rate of the anodic dissolution of metals is much more pronounced than that of the elastic deformation. Hoar and co-workers I4,5] and Hines tTI found that anodic dissolution is highly stimulated by the mechanically induced movement of the surface metal atoms. The influence of macroscopic plastic strain upon the propensity to stress corrosion cracking has been considered by a number of researchers. ~13-2~ Some authors considered that the increasing rate of corrosion or anodic

Preparation process, crystal structure, and physical properties of the 110-K single-phase Pb-Bi-Sr-Ca-Cu-O superconductor.

Abstract: The high-${\mathit{T}}_{\mathit{c}}$ (110-K) superconducting phase in the Pb-Bi-Sr-Ca-Cu-O has been isolated and its structural and physical properties investigated. Transmission-electron-microscopy results show that the structure belongs to a monoclinic system that is different from reports by other groups and in agreement with our x-ray-diffraction analysis. The refined crystal data are a=3.779 \AA{}, b=3.834 \AA{}, c=37.150 \AA{}, \ensuremath{\alpha}=\ensuremath{\beta}=90\ifmmode^\circ\else\textdegree\fi{}, \ensuremath{\gamma}=90\ifmmode^\circ\else\textdegree\fi{} 51', V=538.5 A${\mathrm{\r{}}}^{3}$, space group I112. Based on the resistivity, magnetization, critical-field, and specific-heat measurements, various parameters characterizing the monophase superconductors were determined or derived. Some of them are listed as follows: ${\mathit{T}}_{\mathit{c}\mathit{e}}$ (endpoint)=107 K, ${\mathit{T}}_{\mathit{c}\mathit{m}}$ (midpoint)=110 K, \ensuremath{\Delta}C (specific heat jump at 107 K)=5.3 J/mol K, \ensuremath{\gamma} (the Sommerfeld constant) =34.6 mJ/mol ${\mathrm{K}}^{2}$, FTHETA (Debye temperature)=418 K, ${\mathit{H}}_{\mathit{c}1}$(0)=900 G, ${\mathit{H}}_{\mathit{c}2}$(0)=184 T, and ${\mathit{J}}_{\mathit{c}}$(1.5 K, 0 T)=4.8\ifmmode\times\else\texttimes\fi{}${10}^{4}$ A/${\mathrm{cm}}^{2}$, etc. Morphology, thermal analysis, and pressure effects of the sample are also mentioned.

A new treatment for calculating activities from phase diagrams involving two liquid or solid coexisting phases

Abstract: New formulae for calculating activities and activity coefficients from phase diagram at a fixed temperature are presented for a binary system involving a two liquid or solid coexisting phases. In the new formulae. Richardson's assumption that for many systems Δ H i Δ S E i is approximately equal to 3000, has been adopted. In terms of the new formulae, activities of components in Zn-Pb and Zn-Bi binary systems are calculated and the results show that the formulae are efficient.

A new treatment for calculating activities from phase diagrams containing solid solution

Abstract: A new treatment for calculating activities and activity coefficients of components from phase diagram at a fixed temperature is presented for a binary system involving the liquid and solid solution equilibrium, in which the Richardson's assumption, ΔHi ΔS E i is approximately equal to 3000, has been adopted. The application to the Cu-Ni system shows that this treatment is efficient.

Calculating activities from phase diagram containing equilibrium between solid and liquid solutions

Abstract: A new set of formulae for calculating activities and activity coefficients of components at a fixed temperature in a binary system are presented from the phase diagram involving the equilibria between liquid and solid solutions based on the knowledge of entropies of fusion of components and those of liquidus and solidus compositions. The application of this new method to Cd-Mg system shows that this new method is feasible. It is expected that these formulae will find its applications in alloys, melts and slag, especially when experimental data are not available.

Antiplane eigenstrain problem of a circular inclusion in nonlocal elasticity

Abstract: The antiplane eigenstrain problem of a circular inclusion is investigated in nonlocal elasticity. The nonlocals tress fields are obtained analytically by generalizing the classical line force concept to the case of nonlocal elasticity. The nonlocal effects, stress concentration and nonlocal surface residual, are exhibited for the first time.

Effects of the cooling rate on the microstructures of Ni-27.3 at% Al alloy

Abstract: Etude de l'influence de la vitesse de refroidissement sur la microstructure de l'alliage Ni-27,5 % at. Al solidifie rapidement par le filage a l'etat liquide

Influence of Widening on the Rolling and Recrystallization Texture in High Purity Al with Initial Cube Texture

Abstract: The influence of widening and initial Cube tex- ture on formation of rolling and recrystallization texture was investigated in high purity Al.With in- creasing widening the initial Cube texture has ro- tated more around rolling direction(RD)and less around transverse direction(TD).Therefore,more orientations rotate in x-fibre between G{110} 001and B{110}112positions,and less in S{124}211texture component,which shows the widening plays an important role in the forma- tion of S component during rolling.The relation- ship between rolling and recrystallization texture components is discussed.Though the transition band predicted by Dillamore and Katoh is always formed during rolling,the most important factor in- fluencing recrystallization texture should be the ori- ented growth according to the changes of volume fractions and scatter widths of texture components with widening.

Aluminized coating and AlY and AlCe codeposited coatings obtained by metalliding from molten salt films

Abstract: Metalliding from molten salt films was studied. The salt film is a dispersed system composed of solid and liquid phases. The mass transport in the salt film is through both diffusion and electric migration, but not convection. Because of this, the critical current density required to deposit aluminium is decreased, and the cathodic reactions are controlled by diffusion, which makes AlY and AlCe codeposition easier. there is a critical current density required for yttrium or cerium to be codeposited with aluminium. The AlY and AlCe codeposited coatings have better resistance to high temperature corrosion.

Simultaneous sulphidation and oxidation of Fe-25 wt.%Cr and Silicon-containing Fe-25 wt.%Cr alloys in H2H2OH2S gas mixtures at high temperatures

Abstract: The simultaneous sulphidation and oxidation of Fe-25wt.%Cr and silicon-containing Fe-25wt.%Cr alloys was studied at 1023, 1123 and 1223 K in H 2 H 2 OH 2 S gas mixtures. The kinetic measurement showed a transition from oxide formation with slow mass gains at high P O 2 to sulphide formation with rapid mass gains at low P O 2 . The reaction rates usually decreased with increasing oxygen partial pressure at constant sulphur partial pressure. The critical oxygen partial pressure corresponding to the transition from oxide formation to sulhide formation increased with increasing silicon content of the alloys. The experimental results also showed that simultaneous sulphidation and oxidation appeared in a very large range of oxygen partial pressure. Metastable sulphides can coexist with oxides in the surface of the scale even when the oxygen partial pressure is much higher than the equilibrium pressure. Thermodynamic stability diagrams for (Fe, Cr, Si)SO systems were generated and were used to explain the experimental results. The critical oxygen partial pressures obtained by experiments are systematically higher than those calculated. The influence of silicon on the transition from oxide formation to sulphide formation is discussed and analysed on the basis of thermodynamics and kinetics.

Fatigue-Creep Interaction Fracture Maps and Life Prediction under Combined Fatigue-Creep Stress Cycling

Abstract: The purpose of this paper is to introduce sys- tematically the theory of fatigue-creep interaction fracture map and its application.