A supersaturated single phase ordered α_2 structure in as rapidly quenched al-loys both Ti-42at.-%Al and Ti-45at.-%Al, after solid solution treatment, was revealed un-der observation with optical and transmission electron microscope as well as X-raydiffraction analysis. The supersaturated single phase may transform into a lamellar structureof γ+α_2 with a discontinuous decomposition mechanism in Ti-42at.-% Al alloy and with asemicontinuous decomposition mechanism in Ti-45at.-%Al alloy when it aged isothermallyin the two-phase range between 1000 and 1100℃. The semicontinuous transformation in-volves two process: precipitation of primary lamellar γ phase and subsequent formation ofcellular microstructure, in result, the initial even grain boundaries of α_2 become sawtooth.

A cluster of monocrystalline Ni_3Al has been studied by the discrete variationalXα(DV-Xα) method. From the computation, the energy level structures and the densities ofelectronic states were investigated. The bond order between the constituent atoms and theircomponents have been calculated. The analysis of bond component shows that the Ni-Nibond is very similar to the Ni-Al bond. The Ll_2 structure of Ni_3Al leads these similar bondsto disperse evenly in the space. In macroscopical properties, Ni_3Al exhibits high strength. Theductility of monocrystal is due to the similarity of Ni-Ni bond to Ni-Al bond. The brittlenessof polycrystal is attributed to the weakening of directional covalent bonding at grain bounda-ry.

The experimental results for three selected ternary alloy systems: Ti-Al-V,Ti-Al-Mo and Ti-Al-Nb show that the formation of ω-phase obeys the electron concentra-tion rule. The valence electron number is N_(Ti)=4(s~2d~2), N_v=5(s~2d~3), N_(Mo)=6(s~1d~5),N_(Nb)=5(s~1p~4) for the transition elements Ti, V, Mo, Nb, respectively, and N_(Al)=3(s~2p~1) for thenon-transition element Al. Furthermore, the electronegativities and atomic radii of the al-loying elements will still have some influence upon the ω-phase formation. Sythesizing thevalence electron number, electronegativity and atomatic radius of the alloying element, thecharacteristic value may be fixed at 4.223 in Ti alloy, and which may be expressed as4.223=∑N_if_i+0.310△x / x_(Ti)+0.551 △r / r_(Ti)

Less Ce content in rapidly solidified Al-Ce alloys at a certain cooling rate wasfound to facilitate the formation of granular disperse phase. While the alloys with definitecomposition may easily precipitate globular grains of higher dispersity if the cooling rate wasaccelerated.

Investigations were made of the surface state of amorphous Ni_(63)Zr_(37) alloyribbon and affected by heating under vacuum or in air, prior to grinding or not, by means ofAES, XPS, SAM and SEM combined in situ with Ar ion bombardent. The selective oxidationand surface segregation of Zr were observed on surface layer of as-received ribbon. Highertemperature and higher oxygen pressure are beneficial to oxidation and surface segregation ofNi. Grinding pretreatment may reduce the size of Ni oxide and its precipiation temperatureon ribbon surface. Selective oxidation and surface segregation of Zr may cause the cracking ofribbon surface during oxidation.

The mechanical properties of a ferritic-austenitic duplex stainless steel has beeninvestigated in the temperature range between 600 to 1100℃. The variation of ductilityagainst temperature has a minimum at 800--900℃. While at about 600℃ ferrite deformedcooperatively with austenite. With increasing temperature the coordination decreased. Evenat 1100℃ ferrite dominated the deformation process. The kinetics of σ-phase precipitationand the effect of σ-phase on tensile properties have also been revealed. The ductility of spec-imens deformed at about 600℃ was largely reduced by σ-phase and the effects of σ-phaseincreased with increasing σ-phase fraction but exhibit significant temperature dependence.When a specimen consisting of 16% σ-phase was tested at 900℃, σ-phase particle bandswere realigned parallel to the shearinng directions. Final fracture was preceded by plasticdeformation. At about 1000℃ the effect of σ-phase precipitation on tensile properties disap-peared, while fine dispersion of secondary austenite within ferrite strengthened the materialslightly.

Transformation characteristics of the dendritic austenite and eutectic austenitein commercial grey cast iron during continuous cooling have been investigated. Under exper-imental conditions, the dendritic austenite tends always to transform into pearlite structure,while eutectic austenite may transform into ferrite, pearlite of acicular (bainite andmartensite) structure.

Effects of current pulse on mechanical behaviors and fracture mechanism of2091 Al-Li superplastically deformed at high strain rate have been investigated. Applying adirect current pulse makes the 2091 Al-Li alloy still with high stress-strain rate sensiitivityexponent and superplastic properties under superplastically deformed at high strain rate of10~(-2)s~(-1). SEM observation showed that the fracture for 2091 Al-Li alloy, superplastically de-formed at high strain rate by applying current pulse, transforms from intergranular tear totypical superplastic failure, i. e., fracture by formation and coalescene of cavities at particlesand boundaries.

The life under low cycle fatigue with plastic strain energy for tensile andcompressive fatigue of steel 45: N_f=(W_f / △W)~(1/a),and for torsional fatigue of steel 35: N_f=(U_f / △U)~(1/b)where W and U are plastic strain energy under cycle fatigue, a and b are exponent. The cumu-lative damage ∑(n_i / N_(if))~c=1, where n and N are number of cycle and c is constant.

The reaction product of Ca_2SiO_4-NaFeO_2 system has been investigated byX-ray diffraction and IR spectroscopy. The product contains CaFe_2O_4 and Na_4Ca_8(SiO_4)_5.Thermodynamical estimation also confirms that Ca_2SiO_4+NaFeO_2 is not the stable pair ofthe reciprocal salt pairs of Ca, NaSiO_4, FeO_2 system. In the reactions betweenNa_4Ca_8(SiO_4)_5 and sodium aluminate solution there forms Ca_3[Al(OH)_6]_2 (or its solid solu-tion) which will decrease the recovery of alumina. Based on the abovementioned facts, themathematical model for the optimization of the composition of sinters in alumina productionhas been explained.

Semi-automatic image analysis system is used for fractal dimensionmeasurement of the outline of a rock or ore particle in comminution. The experimental datashow that the fractal dimension of particle surface is in the range of 2.033--2.110, which isslightly higher with finer in particle size. Therefore, according to the theory that energy incomminution is proportional to the fractal surface area of particle, the formula which is sameas Hukki's empirical equation is obtained and is stated as general form of three expressionsbased on the Kick's, Rittinger's and Bond's theory.

At room temperature Fe and Cu form almost no solid solution in equilibriumphase diagram but X-ray diffraction and DTA show that the metastableFe_(1-x)Cu_x supersaturated solid solution can be obtained after 5 h of ball-milling of the mixedFe and Cu powders. The bcc phase is extended over the region with x≤0.10, while the fccphase with x≥0.30. For 0.10 References | Related Articles | Metrics

Study was made of the equilibrium of Ba-O, Ba-S and Ba-P in molten Fe byusing of Ba vapour-liquid Fe system sealed in Mo chamber. Their thermodynamicparameters determined are: △G_(BaO)~o= 188500+38.3T J/mol, e_O~(Ba)=624-1.25×10~6 / T IgK_(BaO)=-2.00-9849 / T △G_(BaS)~o= 469100-111T J/mol, e_S~(Ba)=826-1.64×10~6 / T IgK_(BaS)=5.80-24516 / TAt 1873K, K_(Ba_3P_2)=7.76×10~(-18), e_(Ba)~P=-0.95, AG_(Ba_3P_2)~0=613200 J / mol

Phase diagrams of binary system SmCl_3-PbCl_2 and ternary systemSmCl_3-PbCl_2-CaC_2, have been determined by DTA and X-ray diffraction analyses. In theSmCl_3-PbCl_2 system, an incongruent compound 3SmCl_3-PbCl_2, an eutectic point at 452℃containing 33.0 mol-% SmCl_3 and a peritectic point at 465℃ containing 42.0 mol-%SmCl_3 were obtained. In the SmCl_3-PbCl_2-CaCl_2 system, 4 liquiduses corresponding to theprimary crystallization of SmCl_3, PbCl_2, CaCl_2, and 3SmCl_3·PbCl_2, respectively, 5unvariant lines related to the secondary crystallization, a ternary eutectic point at 396℃ con-taining 29.5 SmCl_3 and 58.0 PbCl_2 by mol-% and a ternary peritectic point at 417℃ con-taining 36.0 SmCl_3 and 50.0 PbCl_2 by mol-% were found. Two reactions corresponding to 4phase equilibriums are L=CaCl_2+PbCl_2+3SmCl_3·PbCl_2 and L+SmCl_3=CaCl_2+3SmCl_3·PbCl_2.

The rapidly quenched Au-17.9at. -%Si ribbon has become twisted, brittle,disappeared from eutectic point and started to melt up to 1341 K after prolongedcrystallization for 3 years under atmospheric environment. This seems to be due to theoxidation of Si in the eutectic of Au-Si into SiO_2.

SCC behaviour of Welten 60 pipeline steel in Na_2CO_3 / NaHCO_3 solutionat 80℃ and -670mV(SCE) have been investigated by means of slow strain rate tests, low fre-quency and fluctuating stress tests, metallographic examination and SEM observation. It wasfound that cracking mode was intergranular, and that threshold stresses obtained by using ta-pered cylindrical tension specimen decreased with decreasing strain rate and fluctuating fre-quency. The data obtained by using single notched plate specimens showed that the greatestcracking velocity(da/dt) is about 3.5×10~(-6)mm/s and the critical stress intensityfactor(K_(ISCC) to SCC is about 32MPam~(1/2).

Grain boundary corrosion of oriented Nb bicrystals with symmetric tiltboundaries has been investigated by use of interference microscope. The corrosion depth, d,increases with misorientation angle, θ, except near some coincidence-site-lattice boundarieswhere minimum cusps appear. For small-angle boundaries, d depends on θ following aRead-Shockley type relationship. The atomistic structure and the local expansion of grainboundaries were calculated using a computer simulation method. The structure dependence ofgrain boundary corrosion is explained in terms of variation in free volume.

X-ray diffraction on Ne implanted AISI 304 austenitic stainless steel revealedboth a tensile strain, which related to implantation itself, and a compressive strain in theunderlying substrate, which can be explained by the existence of Ne bubbles at high pressure.These two strains were measured and the principle and method for measuring it were ex-plained in detail. From the strain point of view, it was used to show the martensitic transfor-mation briefly.

Tensile tests and fractograph of SiC whisker reinforced 2124Al and 2024Alcomposites, fabricated by powder metallurgy, were carried out. The chain-like discontinuousθ(Al_2Cu) precipitates and transitionary layer between SiC whisker and precipitates are re-vealed to distribute on the interfaces. These precipitates may decrease strengthening effect ofSiC whisker and ductility of the composite as whole.