The microstructure in 7050 Al alloy under heat treatment regime T74 has been studied by means of TEM and dynamical diffraction simulation. The alloy is found to contain mainly Al_3Zr superlattice phase, η′precipitate phase ard Al_?-Cu_? Fe constituent phase. The η′phase has a C-face centered orthorhombic crystal structure with a=0.492 nm, b=0.852 nm and c=0.701 nm. The orientation relation- ship between η′phase and matrix is determined as (101)_m//(010)_(η′), [111]_m//[001]_(η′).

TEM analysis and computer simulation of the symmetrical superlattice intrinsic stacking faults (SISFs) in slightly deformed polycrystalline Ni_3Al at room temperature are presented. The symmetrical SISFs are important components of the crystal defects in deformed Ni_3Al alloys; the formation mechanism of the symmetrical SISF can be resulted from the reorientation, dissociation and annihilation of a dipole on {111} plane under applied shear stress.

The inheritance phenomenon of precipitated V_4C_3 in martensitic transformation has been investigated by means of electron diffraction and matrix analysis. A crystallographic orientation relation among austenite, martensite and V_4C_3 carbide was found to be: (010)_A//(110)_M//(010)_(V_4C_3) [101]_A//[111]_M//[101]_(V_4C_3) The V_4C_3 first precipitated in austenite, and then was inherited to martensite. Although ertain orientation relation was kept between V_4C_3 and martensite, the interfacial structural analysis pointed out that the biphase interfacial energy is higher than that determined by Baker-Nutting relation, thus it is metastable. Because the V_4C_3 precipitated along the crystalline defects in austenite, they could be inherited to martensite.

The change of mechanical properties of the 8090 Al-Li alloy influenced by aging is attributed to the change of δ′phase particle size and the precipitation of S′phase. The δ′phase may easily precipitate and rapidly grow, but the S′phase can only precipitate with a longer stage of incubation. The S′phase precipitation would be promoted by cold work prior to aging. The co-precipitation of δ′and S′phases could improve the strength and plasicity of the alloy, for which aging at 190℃ for 20-30 h seems to be optimal. In addition, the precipitate free zone (PFZ) can form at high angle grain boundary and its width is over 200 nm at peak aging condition.But at sub-grain boundary, the formation of PFZ is difficult.

The effect of W content on the mechanical properties at elevated and room temperatures of 12%Cr-W-V-Nb heat resistant steel has been studied. The room temperature tensile properties vary no more with the W content ranged 2.2--3.0 wt%, while the impact toughness decreases continuously with the increase of W content. Increase in W content made the increase of short-term creep rupture strength,but no improvement over long-term one. The effect of increasing W content on the precipitation behaviour is revealed not only to promote formation of Laves phase Fe_2 W and increase of total amount of precipitates, but also to accelerated the coarsening of precipitate after annealed on high temperature reheating. When the precipitate is not yet coarsened as shorter in rupture life, the precipitation hardening effect may be intensified by the increasing of precipitate, so that the high temperature strength may be raised by the increase of W content, while the precipitate may coarsen markedly and the precipitation hardening effect may reduce on heating for sufficient long time.

The serrated flow of LC9 Al alloy with different regimes of heat treatment has been investigated at constant rate of stretching. The critical strain ε_?.at the starting of serrated flow increases with the degree of aging. From those ε_?,the activation energy of the process is 0.63 eV which is consistant with the diffusion activation energy of vacancies in Al. The ε_? decreases while the strain rate ε increases, i. e., with negative strain rate relation. This relation is contrary to that of the annealed samples. It shows that the serrated flow of annealed sample is controlled by deformation vacancies, and that of aged sample is controlled by quenching vacancies. The density and shape of the serrations are changed by aging. The mechanism of the above mentioned results is discussed.

On the basis of stress-strain analysis under cyclic loading, the mechanism, origin and cyclic number of micro-crack nucleation of duplex structure materials, saying ferrite plus martensite, have been experimentally studied and calculated.Both results are in fair mutual agreement. The morphology, distribution, size and relative quantities of the constitutional phase, especially strengthening phase, as well as the stress-strain distribution and variation in the micro-region are directly influential in the origin of micro-crack in duplex structure materials.

An investigation was carried out of the morphology and microstructure of V-Ti complex carbonitride in 09MnVTiN microalloyed steel during reheating under analytical electron microscope. The prior V-rich ellipsoid V-Ti complex carbonitride particles are replaced progessively by Ti-rich cubic ones as the reheating temperature elevated from 1050 to 1400℃. The Ti contents in the core and border of particles increase from 15 and 6％ as hot-rolled state into 84 and 94％ at 1400℃ respectively.

The surface yield strength, σ_(ms), of different high carbon alloy steels,examined by X-ray diffraction method, is far lower than the bulk one. It will reflect the parameter for resistance to surface plastic deformation. The smooth fatigue limit,σ_(-1), of materials, which is almost controlled by the crack initiation, should be associated with the damage of accumulation and the resistance against crack initiation.Experimental results show that the relations of σ~(ms)=(0.81-1.02)σ_(-1) for 50％ survival and σ_(ms)=(0.98-1.1)σ_(-1) for 99.9％ survival are exhibited for different types of steels. It seems to be much easier to etermine the surface yield strength than the fatigue limit, and an application for engineering purposes might be available.

The high-cycle fatigue performance of different microstructures of aluminide coating-superalloy system has been studied at 900℃. The single phase coating of coarse equiaxial grain NiAl (β) has unfavourabie effect on fatigue life of the coating-superalloy. The fatigue life may shorten if the coating of NiAl (β) was an enrichment of coarse refractory metal grains. While an improvement can be made by dispersing numerous secondary phase particles such as extreme fine γ', quasi-σ phase and others.

Based on the sequent tracking observation on spalling of GCr15 bearing steel under rolling contact fatigue, an expression for estimating the propagation of subsurface cracks was derived. The rolling contact fatigue life was found to be markedly related the subsurface crack propagation angle. A new explanation of reason why the rolling contact fatigue life can be prolonged by residual compressive stress and retained austenite was advanced.

The morphology and structure of δ eutectoid and the transformation of δ austenite in high speed steel have been studied under SEM and TEM. The δ eutectoid in as-cast high speed steel is rod-shaped eutectoidic units with different orientations and is markedly surrounded by carbide shell. The eutectoidic carbide is rod-shaped M_6C of square cross section. The eutectoid austenite may transform into pearlite structure during cooling.

The hexagonal Co catbide with lattice parameters α=0.2685 nm and c=0.4335 nm was first found when 50 keV carbon ion implanted in thin Co film at the dose of 2.5×10~(17)/cm~2.The hexagonal diffraction ring can remain still at the dose of 5× 0~(17)/cm~2 and then became haloes at 9×10~(17)/cm~2. The stoichiometric composition of the carbide was identified by Auger spectra as Co_(2-3)C. The explanations were proposed on the behaviour of ferromagnetic carbides along the dearending sequence of Ni-Fe-Co by Fermi energy of solids and on the formation of orthogonal Co carbide under thermal processing by the band theory.

The principal reason of the intergranular embrittlement in plasma carburized lay-er on 20Cr2Ni4A steel, analyzed by TEM and Auger spectra, was revealed to be due to the segregation of S, P and other impurities along prior austenite grain boundaries. The retained austenite in the layer is unrelated to the intergranular fracture caused in the region. However,the segregation of impurities may be eliminated by reheating and quenching.

The temperature dependence of critical strain for serrated yielding was found inhigh strength Al-Zn-Mg-Cu alloy. It divides into two temperature regions. Their temperaturecoefficients of critical strain will be negative and positive respectively.

The formation reason and elimination method of non-uniform microstructure defects in TC11 Ti alloy bar have been studied. The coagulating and coarsening into block of the part of grain boundary α and secondary α seem to be caused by the ingot cogging and initial forging temperature in the β region as well as no more enough deformation and uneven distribution. The grain α, elongated α and blocky α may be finally eliminated by adopting the technique of (α+β) thermomechanical processing+β processing, W. Q.+recrystallization annealing, A. C., thus the size of uniform and fine equiaxed α structure is believed to be reduced to 1.9258μm.

A new technique for the measurement of B diffusivity in B bearing alloys by particle tracking autoradiography after deboronization has been established with high sensitivity, good reprocibility and fair simplicity. Experimental results show that the Mo addition up to 3％ into Ni may accelerate the B diffusion in the range of 900—1250℃ and reduce both the activation energy and the frequency factor, of B diffusion but no more influential as the Mo added down to 0.5％.

On the basis of experimental results of 76 points of composition and previous relevant conclusions, a complete structural zoning diagram of solid solution treating Fe-Mn-C system alloy at 1000℃ has been constructed with austenite zones of different stabilities. The chemical composition range and structure change of various Mn steels have also been discussed. Thus, the reasonable selection of composition and structure may be available for the Mn steel with commercial purposes.

Investigation was carried out of the crack growth rate in weld metal and heat affected zone (HAZ) of offshore structural steels, homemade steel 36Z together with foreign steel A537 of similar strength grade by comparison, in artificial sea water undergone fatigue with different frequencies. The crack growth rate in weld metal and HAZ of steel 36Z fatigued at low frequency may be 3-5 and 4-10 times that at high frequency respectively. The crack growth rate for steel 36Z may fairly match that of A537. The crack growth model and fracture feature of weld metal in corrosive medium were also discussed.

A series of mixed mode tests were carried out on 18-8 stainless steel in boiling 42％ MgCl_2 solution. The results show that for any K_(II)/K_I ratio, the SCC direction coincides well with the crack tip maximum normal stress plane, while the SCC resistance of the material reduces as the ratio of K_(II)/K_I increases. The experimental results were discussed in the light of anode dissolving mechanism and the effect of mixed mode loading on crack tip stress and strain. It is concluded that for fracture analysis if mixed mode cracks were simply taken into account as mode I cracks, and only mode Ⅰ testing results as well as mode Ⅰ fracture criterion were employed, it may not be safe.

The composite coating of (N~++IP)-TiN was prepared by ion-plated TiN film onto ion-nitrided case on the low carbon steel substrate. The microhardness measurement along interface between IP-TiN coating and substrate was detected as a moderate decrease in magnitude with increase of distance from the coating surface.This seems due to the occurrence of ion nitride case, ε-Fe_3N-Fe_2N and Fe_4N phases, along the interface.

The stress-strain relation for cast low alloy carbon steel at solidification temperature has been examined by the authors' own designed apparatus for rheological properties measurement. The rheology model, the stress-strain constitutive equation and the rheological parameters therefrom of the cast steel were proposed. Thus the theoretical basis and calculating data for computerized simulation on the stressstrain relation and thermal cracking of the cast steel were suggested.

The amorphous and crystalline Nd-Fe-B films were prepared by RF sputtering at different substrate temperatures. The crystalline specimens, prepared at 600℃ have strong perpendicular anisotropy and high coercivity. And the cystallized alloy from amorphous state has strong perpendicular anisotropy too.

An addition of Nb up to 2 at.-％ into (Nd, Dy)-(Fe, Co)-B alloy causes to form the primary lath Fe_2Nb crystallization and to precipitate the hard magnetic grain. Both increases with the increasing Nb content. During sintering, part of Fe_2Nb dissolves within the 2:14:1 phase, and the Fe_2Nb along grain boundary hinders the growth of 2:14:1 grain. In annealing processing, the dissolved Nb in φ phase precipitates out, and this nearby the grain boundary diffuses into Nd-rich phase to form new Nb-containing grain and to increase the Nb content in Nd-rich phase.

Characteristics of magnetic hardening in cast-hot pressed magnetPr_(19)Fe_(74.5)B_5Cu_(1.5) were studied. The microstructure features and virgin magnetization curve reveal a nucleation controlled coercivity mechanism. Regression analysis shows that the intrinsic coercivity varies inversely as the logarithm of the average grain size: _iH_c(MA/m)=1.7312-0.4816lnd(μm) which confirms the randomness of nucleation of reversed domains and the statistical nature of coercivity, indicating that the decrease of grain size would reduce the average number of defects on its surface and lower the probability of magnetization reversal of a grain and the cumulative fraction of the grains that have reversed their magnetization. Coercivity is thus enhanced.

The XPS spectra of superconducting (123-orthorhombic structure) and non-superconducting (123-tetragonal structure) YBa_2Cu_3O_(7-x). ceramics were obtained at room temperature and 130 K in RIBER LAS 3000 surface analysis system, in which a sample cooling stage and a surface cleaning scraper, both made by the authors'own, were installed. No evidence of Cu~(3+) was found. The O1s shows double lines.They are attributed to O1 and O4 with higher binding energy and to O2 and O3 with lower binding energy respectively, and it was confirmed by calculation of SW-X_α method. The differences and changes in valence states of Y, Ba, Cu and O in both samples were discussed.

The direct reduction of galena with hydrogen at 873-973 K could be described by the shrinking core model in the chemical control region. The reaction was revealed to be of first order with respeot to hydrogen concentration and the activation energy is 79.0 kJ/mol. Because of the fairly large interface tension between the solid galena and the liquid Pb, the SEM second electron images showed that the liquid Pb film is difficult to be formed on the unreacted galena surface in reaction process.

An EPMA was carried out of the concentration distribution of alloying eleme1ts,such as Al, Sn, V, Si and Mo, in surface layer of molten Ti alloy, TC4, TA7 or TC9, which was melted and evaporized by electron beam in water cooling copper crucible. The activity coefficient of the alloying elements was calculated as: γ_(Al)—0.009—0.018 and γ_(Sn)=0.066—0. 123 at 1921—2106℃, γ_v=0.713 at 2021℃, γ_(Si)=0.020, γ_(Mo)=0.913 at 1921℃. The controlling step of evaporation rate of the alloying element Al, Sn, V, Si or Mo was also discussed in the light of relevant evaporation activation energy of such alloying element.

The structure and behaviour of LiF-KF solution, as atypical common-anion system, has been simulated by Monte Carlo method. The calculation of partial radial distribution function of ions, heat of mixing and potential energy distribution shows that the average distance between Li~+ and F~- ions will significantly narrow after molten LiF and KF mix up. This is very similar to the lean-on-one-side effect in moten LiF-KCl solution. The calcu1ated heat of mixing is in fair agreement with the measured one. The dominant source of the energy of mixing may be that the decrease of the repulsion energy between cations, the decrease of the attraction energy between cations and anions, and the decrease of the repulsion energy between anions.

TEM observation on the ionitriding layer was carried out of 3 different steels W18Cr4V, 38CrMoAl and 1Cr18Ni9Ti. And AES of elementary analysis was also made of the outer surface of ionitiding layer on austenite stainless steel. Perhaps due to the ion-bombardment effect, a microcrystalline strucure with texture was affirmed along surface of the ionitriding layer. It may be affected by cathodic sputtering and adsorption that the atomic ratio of Cr/ Fe increases and of Ni/Fe decrease on surface of nitriding layer on austenitic stainless steel 1Cr18Ni9Ti, thus the α-phase microcrystalline structure is also occurred.