Comparison on Hot Tearing Behavior of Binary Mg–Al,Mg–Y,Mg–Gd,Mg–Zn,and Mg–Ca Alloys

Metallurgical and Materials Transactions A - Mg–1Al, Mg–0.9Y, Mg–2Gd, Mg–1.5Zn, and Mg–0.5Ca binary alloys were chosen to clarify the hot tearing mechanism since they...     

NUCLEAR MAGNETIC RESONANCE STUDIES OF METAL COMPLEXES WITH ETHYLENEDIAMINE-N,N′-DIACETATE-N,N′-DI-β-PROPIONATE

The complexes of metals(Mg,Ca,Sr,Ba,La,Y and Lu)with ethylenediamine-N,N′-diacetate-N,N′-di-β-propionate have been studied by proton nuclear magnetic resonance(PMR).The interestingquartet spectral pattern of acetate protons and multiplet spectral pattern of protons of propionate groups forthe complexes of metal ions of high charge density have been observed.The results show that the chemicalbond for these complexes is predominantly ionic and the lability of metal-nitrogen bond as well as metal-oxygen bond decreases with increasing charge density of cations.     

Phase composition,texture, and anisotropy of the properties of Al–Cu–Li–Mg alloy sheets

The formation of the anisotropy of the mechanical properties, the texture, and the phase composition of thin-sheet Al–4.3Cu–1.4Li–0.4Mg and Al–1.8Li–1.8Cu–0.9 Mg alloys have been studied by X-ray diffraction and tensile tests. Various types of anisotropy of the strength properties of the alloys have been revealed: normal anisotropy (strength in the longitudinal direction is higher than that in the transverse direction) in the Al–4.3Cu–1.4Li–0.4Mg alloy and inverse anisotropy in the Al–1.8Li–1.8Cu–0.9Mg alloy. It is shown that the anisotropy of the strength properties is dependent not only on the texture of a solid solution, but also on the content and the texture of the δ' (Al₃Li) and T1 (Al₂CuLi) phases and their coherency and compatibility of deformation with the matrix.     

A Study on Hot Tearing Susceptibility of Al–Cu,Al–Mg,and Al–Zn alloys

The present investigation deals with the hot tearing susceptibility of A206, A518, and A713 alloys. The hot tearing tests of the mentioned alloys were conducted at three different pouring temperatures using sand mold casting. Metallic cores designed to facilitate constrained radial contraction of the aforementioned alloys were used for casting. Macroscopic cracks were found in all the samples except in A518 alloy. It was observed that pouring temperatural and grain size have significant effect on crack susceptibility. Among the investigated alloys, A713 was found to be extremely prone to hot tearing. The microstructure characteristics of the alloys were studied using optical and scanning electron microscopy. Relationships between the pouring temperature, grain size and crack lengths of the alloys were also established.     

Density and Dynamic Viscosity of Sn,Sn–Ag,and Sn–Ag–Cu Liquid Lead-Free Solder Alloys

Powder Metallurgy and Metal Ceramics - Traditionally, the soldering process was carried out, applying mainly lead-based solder materials. However, the prohibition against using lead (Pb) in...     

The Influence of Synthesis Conditions on the Phase Composition,Structure, and Properties of the High-Entropy Ti–Cr–Fe–Ni–Cu Alloy

Powder Metallurgy and Metal Ceramics - The influence of production conditions on the structure, phase composition, and properties of the high-entropy Ti–Cr–Fe–Ni–Cu alloy...     

Phase Composition,Texture, and Residual Stresses in Al–Cu–Li Friction Stir Welds

The formation of the phase composition, the texture, and the residual stresses in the V-1469 alloy joint (Al–Cu–Li system) fabricated by friction stir welding is studied. A numerical correlation between the phase composition, the hardness, and the residual stresses in various zones and sections of the welded joint is found     

Development of the γ′ Stability in Co–Al–W Alloys at 800 °C by Alloying with Carbon

Metallurgical and Materials Transactions A - The microstructures and hardnesses of Co–10Al–9W–1C, Co–7Al–5W–1C, and Co–7Al–5W (at. pct) alloys are...     

Synthesis of 2, 6-Bis(1′-Phenyl-3′-Methyl-5′-Oxopyrazole-4′) Pyridinediacyl and Its Solid-Liquid Extraction Behavior for Ce(Ⅲ)

1 Ｐｈｅｎｙｌ 3 ｍｅｔｈｙｌ 4 ａｃｙｌｐｙｒａｚｏｌ 5 ｏｎｅｄｅｒｉｖａｔｉｖｅｓａｒｅｗｅｌｌｋｎｏｗｎａｓβ ｄｉｋｅｔｏｎｅｔｙｐｅｃｈｅｌａｔｉｎｇｌｉｇａｎｄｓｃｏｏｒｄｉｎａｔｉｎｇｔｏａｍｅｔａｌｉｏｎｗｉｔｈｏｘｙｇｅｎａｔｏｍｓａｓ“ｈａｒｄ”Ｌｅｗｉｓｂａｓｅｓ .Ｄｏｎｇｅｔａｌ .[1 ] ａｎｄＹａｎｇｅｔａｌ .[2 ] ｗｅｒｅｓｙｎｔｈｅ ｓｉｚｅｄａｓｐｅｃｉａｌｆａｍｉｌｙｏｆｂｉｓ( 4 ａｃｙｌｐｙｒａｚｏｌ 5 ｏｎｅ)ｄｅｒｉｖａｔｉｖｅｓ ,ｉｎｗｈｉｃｈ ,ｔｗｏ 1 …     

Temperature Dependence of the γ/γ′ Interfacial Energy in Binary Ni–Al Alloys

Published data on the coarsening kinetics of γ′ (Ni₃Al) precipitates in binary Ni–Al alloys aged at 12 temperatures ranging from 773 K to 1073 K are analyzed to provide a comprehensive evaluation of the temperature dependence of the γ/γ′ interfacial free energy, σ. The data are analyzed using equations of the trans-interface-diffusion-controlled (TIDC) theory of coarsening, with temporal exponent n = 2.4. The results show that σ decreases with increasing temperature, T. A linear empirical equation is fitted to the data on σ vs T; it extrapolates to σ = 0 in the liquid region of the Ni–Al phase diagram, as it should do. A quantitative temperature-dependent transition radius, r_trans, is calculated; it depends on the product of the interface width and the ratio of the chemical diffusion coefficients in the γ phase and interface regions. Applying the TIDC coarsening equations to calculate σ is justified when the average radius, 〈r〉, satisfies the condition 〈r〉 < r_trans, which is valid for all the data used in the fit. The data on σ vs T are compared with theoretical predictions. The results are discussed in the context of previous work, as well as with values of σ obtained through analyses using the equations of traditional LSW coarsening kinetics, n = 3.

     

Stability of Rare Earth Ion-N, N′-bis（2′-Pyridine）methyl-1,10-Phenanthroline-2,9-Dimethanmine Binary Complexes

1 ,10 Phenanthrolinehasbeenextensivelyusedasanazaheterocyclicchelateligandinbothanalyticalandpreparativecoordinationchemistry[1] .Asanim portantligand ,1,10 phenanthrolineunitplaysanim portantroleforthedevelopmentofthesupramolecularchemistry .Manynovelsupramolecularcompoundsin clude 1,10 phenanthrolineunit[2～ 4 ] .Furthermore ,consideringtheuniquecombinationofchemicalstabil ities ,redoxproperties ,luminescenceemissionandex citedstatelifetime ,derivativesof 1,10 phenanthrolinehaveplayedama…     

Role of Ti on Phase Evolution,Oxidation and Nitridation of Co–30Ni–10Al–8Cr–5Mo–2Nb–(0, 2 & 4) Ti Cobalt Base Superalloys at Elevated Temperature

Titanium is an important alloying addition to γ/γ′ cobalt-based superalloys that enhances the high temperature microstructural stability and make the alloys lighter. In this work, we probe the role of Ti composition on the phase stability and oxidation behavior of Co–30Ni–10Al–8Cr–5Mo–2Nb superalloys. With Ti addition, the γ′-solvus temperature is enhanced and the γ′-precipitate shape changes from spherical to rounded cuboids. Addition of 4 at. pct Ti to the alloy promotes topologically-close-packed (TCP) phase formation that are rich in Co, Cr, and Mo. During oxidation at 900 °C, Ti was found to facilitate the early formation of passivating oxide layers (spinel CoCr₂O₄/CoAl₂O₄) on the exposed surfaces, however, it was not effective in reducing the oxidation-induced mass gain. Microstructural analysis reveals that Ti delays the Al₂O₃ layer formation eventually leading to faster oxidation kinetics. Additionally, we also found formation of (Ti,Nb)N in the γ′ denuded zones near the alloy-oxide interface.

     

′99经济热点

国家信息中心前不久举行了1999年经济预测调查,有关专家对当前一些热点经济问题进行了预测:     

Sintering,microstructure, and mechanical properties of PM manganese–molybdenum steels

Abstract

The effects of 0·5 wt-%Mo addition on the processing, microstructure, and strength of PM Fe–3·5Mn–0·7C steel are described. Water atomised and sponge irons, Astaloy 1·5Mo, milled ferromanganese, and graphite were the starting powders. During sintering in 75H₂ /25N₂ or pure hydrogen the dewpoint was controlled and monitored; in particular the effects of improving it from -35 to -60°C were investigated. Faster heating rates (≥20 K min^-1), sufficient gas flowrates, milling the ferro alloy under nitrogen, a low dewpoint (<-60°C), and a getter powder can all contribute to the reduction or prevention of oxidation of the manganese, in particular formation of oxide networks in the sintered steels. For 600 MPa compaction pressure densities up to 7·1 g cm^-3 were obtained; these were not significantly affected by sintering at temperatures up to 1180°C. The sintered microstructures were sensitively dependent on the cooling rate. Irrespective of the presence of Mo, slow furnace cooling at ～4 K min^-1 resulted in mainly pearlitic structures with some ferrite and coarse bainite, whereas fast cooling at ～40 K min^-1 produced martensite and some retained austenite, very fine pearlite, bainite, and some ferrite. Young's modulus, determined by tensile and ultrasonic tests, was in the range 110–155 GPa. Sintering with -60°C dewpoint resulted in tensile and transverse rupture strengths of420 and 860 MPa for the Mn steel, rising to 530 and1130 MPa as a result of the Mo addition. This contrasts with strength decreases observed when processing included use of high oxygen containing ferromanganese and sintering with -35°C dewpoint.     

Parental beliefs, infant temperament, and marital quality: Associations with infant–mother and infant–father attachment.

The present research examined parental beliefs about the importance of the paternal caregiving role, mothers’ and fathers’ reports of infant temperament, and observed marital quality as predictors of infant–mother and infant–father attachment security, over and above the effects of parental sensitivity. Infants’ attachment security to mothers and fathers were observed in the Strange Situation at 12 and 13 months, respectively (N = 62 two-parent families). Hierarchical regression models revealed that mothers who viewed the paternal caregiving role as important were less likely to have securely attached infants, but only when infant fussiness was high. In addition, fathers who viewed the paternal caregiving role as important were more likely to have securely attached infants, but only when infants’ fussiness or marital quality was high. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Industrial processing,microstructures and mechanical properties of Fe–(2–4)Mn (–0.85Mo)–(0.3–0.7)C sintered steels

Abstract

The potential of PM Mn steels has been established in laboratory experiments. This paper deals with sintering of Fe–(2–4)Mn–(0.3/0.7)C, also with 0˙85%Mo addition, in an industrial pusher furnace at 1180°C in an atmosphere of 25% hydrogen plus 75% nitrogen, obtained from a cryogenic liquid, giving an inlet dew-point of ?55 °C. Tensile, bend (including fatigue) and miniature Charpy specimens were sintered in flowing gases and in semiclosed containers with a getter of ferromanganese, carbon and alumina. The quenched and tem- pered state was investigated, as was sinter hardening (cooling rate of 55 K min ?1), simulated for comparison with slow cooling at 10 K min ?1. As there was no forma tion of oxide networks at the combination of sintering temperature and dewpoint, in accordance with the Ellingham–Richardson diagram for Mn oxidation/reduction, the use of semiclosed containers was superfluous. The quenched and tempered specimens were brittle. Sinter hardening lead to an improvement in mechanical properties. The reproducibility of tensile and TRS data was high for the sintered materials, characterised by Weibull moduli m of 12–41. All the alloy microstructures were complex and heterogeneous, consisting of, depending on the local manganese and carbon contents, the diffusive and non-diffusive transformation products (pearlite, bainite, martensite) and additionally ferrite and retained austenite. The highest mechanical properties in the entire range of compositions investigated in the furnace cooled state: yield, tensile and bend strengths of 499, 637 and 1280 MPa, respectively, with impact energy of 18 J, and tensile and bend strains of 1˙17 and 1.57%, were achieved for the Fe–2Mn–0.85Mo–0.5C alloy, marginally superior to Fe–2Mn–0.7C. For the sinter hardened Fe–4Mn–0.3C alloy yield, tensile and bend strengths were 570, 664 and 1263 MPa, respectively, at an acceptable impact energy of 14 J, with tensile and bend strains of 0.52% and 1.8%. Many of the results compare favourably with the requirements of MPIF standard 35. Mn is a more effective strengthening agent than either Ni or Cu, or their combination, though generally at reduced plasticity.     

Deposition,Characterization and Evaluation of Monolayer and Multilayer Ni,Ni–P and Ni–P–Nano ZnO<Subscript>p</Subscript> Coatings

Ni, Ni–P and Ni–P–ZnO_p monolayer films along with multilayer coatings containing different arrangements of these layers were produced on steel substrates by electrodeposition and electroless deposition techniques. Co-deposition of ZnO nano-particles, as well as morphology, cross-section, microstructure and microhardness of coatings were investigated. Corrosion behaviors of monolayer coatings were studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques, and the results were compared to multilayer films. Results revealed that, Ni–P–1.5 vol% ZnO_p monolayer film obtained from a bath with 4 g L^?1 of these particles had the highest hardness between all samples. Further addition of nano-particles to the bath lead to the formation of discontinuous films. Most of the multilayer coatings with different arrangements exhibited higher corrosion resistance as compared to monolayer films. Corrosion current density of three-layer Ni–P–ZnO_p/Ni/Ni–P coating, considered as the most corrosion resistant film, was about 538 times lower than monolayer Ni–P coating.