Sulfidation under atmospheric conditions of Cu-Ni,Cu-Sn,and Cu-Zn binary and Cu-Ni-Sn and Cu-Ni-Zn ternary systems

The corrosion susceptibility of binary and ternary alloys can be assessed by controlled exposures to corrosive environments of samples selected from different regions of the phase diagram. To conduct such studies, we have prepared 24 high purity alloys from the Cu-Ni, Cu-Sn, and Cu-Zn binary and Cu-Ni-Sn and Cu-Ni-Zn ternary systems. Samples of these alloys were then exposed for varying periods to atmospherically realistic concentrations of hydrogen sulfide in humidified air. The resulting sulfurization of the samples is presented in a series of chromatic plots developed as part of this research. The ability of binary alloying metals to retard the sulfidation of copper follows the order Zn > Ni > Sn. The Cu-Ni-Zn ternary alloys are more resistant to sulfidation than Cu-Ni-Sn alloys for the same extent of solid solution alloying; in fact, alloys in the Cu-Ni-Zn system with ≤70 pct copper proved to be extremely resistant to sulfidation. In both ternary systems, the relative performance of the alloys was different at different exposure periods, a result that emphasizes the importance of monitoring corrosion throughout realistic exposures if the results are to be used in the selection of materials for field applications.     

Application of the diffusion couple to study phase equilibria in the Fe-Cr-S ternary system at 600 °C

The sulfidation of Fe-Cr alloys has a large financial significance for industries that use fossil fuels, such as the electric utility industry. Therefore, the sulfidation of a series of Fe-Cr alloys was studied at 600 °C using a solid-state diffusion couple technique. The diffusion couple technique combined Fe_0.95S powder and FeCr binary alloys together in a configuration that allowed for post-heat-treatment microanalysis using an electron probe microanalyzer (EPMA). The results showed that only two different diffusion couple microstructures formed in samples spanning the entire Fe-Cr binary range. The Fe-rich alloy diffusion couples contained a surface αFeCr layer and an internal sulfide precipitate layer that contained three different sulfide phases. The Cr-rich alloy diffusion couples also possessed an internal precipitate layer, as well as a thick, triplex interfacial scale. The ternary elemental diffusion was described using diffusion paths plotted on the 600 °C isothermal section of the Fe-Cr-S phase diagram. The results also showed that samples with less than 51 wt Pct Cr were more sulfidation resistant. The accuracy of the existing Fe-Cr-S 600 °C isothermal section was assessed, and it was determined that the τ phase field had a larger composition than previously published.     

The Co-Cr-S ternary system at 1223 K and applications to corrosion

Ternary phase relations in the Co-Cr-S system at 1223 K were determined using microprobe analysis of quenched samples. The results are consistent with the data available on the binary systems. A complete solid solution exists between cobalt monosulfide and chromium monosulfide. The CoCr₂S₄ thiospinel is the only ternary compound formed. A sulfur potential diagram was constructed for the region involving equilibrium between alloy and monosulfide based on thermodynamic data on the Co-Cr, Co-S, and Cr-S binary systems and the ternary information obtained in this study. The sulfidation behavior of Co-Cr alloys reported in the literature is discussed in light of the sulfur potential diagram. Formerly at the Department of Metallurgy and Materials Science, University of Toronto     

Diffusion of the tracers Cu67, Ni66, and Zn65 in copper-rich solid solutions in the system Cu-Ni-Zn

Tracer diffusion coefficients were determined for the three isotopes, Zn⁶⁵, Cu⁶⁷, and Ni⁶⁶, in homogeneous Cu-Ni-Zn binary and ternary alloys, to 30 pct Ni and Zn, and pure copper as a function of composition and as a function of temperature, within about 250°C of the solidus surface. Activation energies andD ₀ factors were determined as functions of composition from these measurements. It is found that as the composition plane is traversed in the general direction from high nickel compositions on the copper-nickel binary to high zinc concentrations on the copper-zinc binary,i.e., as nickel is replaced by zinc, the diffusivity of all three tracers increases, and the activation energy for diffusion decreases. The total change in diffusivity across the composition plane is about two orders of magnitude. The three diffusivities are always in the order:D*_Zn >D*_Cu >D*_Ni, with the ratio being 9∶3∶1 at 900°C for all compositions. The three activation energies are usually in the orderQ*_Ni >Q*_Cu >Q*_Zn. These results are shown to be consistent with atom size and electron-to-atom concentrations of the three species in this alloy system. K. J. ANUSAVICE, formerly Graduate Student, Department of Materials Engineering, University of Florida, Gainesville, Fla.     

Investigation of the processes of obtaining plastic treatment and electrochemical behaviour of lead alloys in their capacity as anodes during the electroextraction of zinc I. Behaviour of Pb---Ag, Pb---Ca and PB---Ag---Ca alloys

The influence of the mode of obtaining and plastic treatment of binary Pb---Ag and Pb---Ca, and ternary Pb---Ag---Ca alloys (used as anodes in Zn electro-extraction from sulphate electrolytes) on their electrochemical behaviour and corrosion resistance is studied.It has been established that the rolled Pb---Ag alloys possess a higher corrosion resistance and lower anodic polarization compared to the cast lead-silver ones due to the structural fineness and homogeneity of the plastic deformed anodes. The plastic deformation of the ternary alloys with calcium content of 0.06% causes Pb₃Ca precipitation in the solid solution. The hot-rolled alloys form an solid solution of Pb₃Ca with fine-grained structure, deformed through the rolling direction. The cold-rolled alloys possess clearly expressed oriented structures also through the rolling direction.Cast and plastically deformed Pb---Ca anodes possess better electrochemical and corrosion characteristics than pure Pb but a considerably higher anodic polarization and lower corrosion resistance than Pb---Ag alloys. Both Pb---Ca systems, with a calcium content of 0.08 and 0.11 % are very appropriate for the preparation of ternary Pb---Ag---Ca alloys. These alloys (Pb---Ag 0.5 %-Ca 0.11 %) possess better electrochemical and corrosion characteristics than binary Pb---Ca ones. Only ternary rolled alloys have equal corrosion and electrochemical properties to those of the alloy Pb---Ag (0.75%–1.0%) used in practice.     

Investigation of the processes of obtaining plastic treatment and electrochemical behaviour of lead alloys in their capacity as anodes during the electroextraction of zinc I. Behaviour of PbAg, PbCa and PBAgCa alloys

The influence of the mode of obtaining and plastic treatment of binary PbAg and PbCa, and ternary PbAgCa alloys (used as anodes in Zn electro-extraction from sulphate electrolytes) on their electrochemical behaviour and corrosion resistance is studied.It has been established that the rolled PbAg alloys possess a higher corrosion resistance and lower anodic polarization compared to the cast lead-silver ones due to the structural fineness and homogeneity of the plastic deformed anodes. The plastic deformation of the ternary alloys with calcium content of 0.06% causes Pb₃Ca precipitation in the solid solution. The hot-rolled alloys form an solid solution of Pb₃Ca with fine-grained structure, deformed through the rolling direction. The cold-rolled alloys possess clearly expressed oriented structures also through the rolling direction.Cast and plastically deformed PbCa anodes possess better electrochemical and corrosion characteristics than pure Pb but a considerably higher anodic polarization and lower corrosion resistance than PbAg alloys. Both PbCa systems, with a calcium content of 0.08 and 0.11 % are very appropriate for the preparation of ternary PbAgCa alloys. These alloys (PbAg 0.5 %-Ca 0.11 %) possess better electrochemical and corrosion characteristics than binary PbCa ones. Only ternary rolled alloys have equal corrosion and electrochemical properties to those of the alloy PbAg (0.75%–1.0%) used in practice.     

Structure and physicomechanical properties of melt-spun TiNi-based alloys

The structure and physicomechanical properties (strength, plasticity, electrical resistivity, and shape memory effect) of TiNi-based binary (stoichiometric and nonstoichiometric compositions) and ternary (alloyed with copper, iron, and cobalt) alloys are studied in the initial (after melt quenching (MQ)) and annealed states. It is shown that the structural states formed upon MQ in all alloys are dependent on the cooling rate; subsequent heat treatment; and the contents of titanium, nickel, and alloying elements. Depending on the chemical compositions, MQ alloys undergo thermoelastic martensitic transformations with the formation of the R, B19′, or B19 martensite.     

铜合金的腐蚀与防护研究进展

铜合金具有良好的导电性和导热性,是应用最广泛的工业材料之一。铜合金服役过程中常与酸、碱、盐等腐蚀介质接触,易引起铜合金的腐蚀,最终导致失效,对生产制造带来危害。提高铜合金的耐腐蚀性有利于进一步扩展其应用领域。本文主要归纳了Cr, Pb, Ti, Al,Mn, Ni以及稀土元素的添加对合金耐蚀性能的影响,通过合金元素的添加可以改变铜合金表面腐蚀产物膜的组成和形貌,减小相与相之间腐蚀电位差,以及减少有害杂质的存在,以此来改善铜合金的耐蚀性能。塑性变形和热处理是改善铜合金力学性能的常用手段,经塑性变形和热处理过后的铜合金,其微观组织形貌和分布发生了变化,因此对合金耐蚀性能也有一定的影响。本文主要从合金化、塑性变形及热处理3个方面对铜合金耐蚀性能影响进行综述,最后对铜合金的腐蚀防护研究进行总结和展望。     

Warm-temperature tensile ductility in Al-Mg alloys

Several binary and ternary Al alloys containing from 2.8 to 5.5 wt pct Mg were tested in tension at elevated temperatures (200 °C to 500 °C) over a range of strain rates (10⁻⁴ to 2.0 s⁻¹). Tensile ductilies of up to 325 pct were obtained in binary Al-Mg alloys with coarse grains deformed in the solute-drag creep regime. Under test conditions in which solute-drag creep controls deformation, Mg in concentrations from 2.8 to 5.5 wt pct neither affects tensile ductility nor influences strain-rate sensitivity or flow stress significantly. Strength is shown to increase with increasing Mg concentration, however, in the power-law-breakdown regime. The solute-drag creep process, which leads to superplastic-like elongations, is shown to have no observable grain-size dependence in a binary Al-Mg material. Ternary alloying additions of Mn and Zr are shown to decrease the strain-rate sensitivity during solute-drag creep, negatively influencing ductility. An important cause of reduced ductility in the ternary alloys during creep deformation is found to be a transition from necking-controlled failure in the binary alloys to cavitation-controlled failure in the ternary alloys investigated. An increase in ternary element concentration, which can increase the relative volume percentage of proeutectic products, increases cavitation.     

流动和污染海水诱发并加速铜合金脱成分腐蚀的研究

分析了研究了4种铜合金在舟山、青岛、榆林各海水腐蚀试验站暴露4年以上的腐蚀数据,得到流动海水和污染海水对铜合金脱成分腐蚀的基本规律和机理,双相黄铜及硅青铜对流动海水的腐蚀最为敏感,从前者的脱成分腐蚀机理出发,提出了流动诱发和加速铜合金脱成分腐蚀的新概念。其关键在于,随着原始表现膜的腐蚀消耗,不能形成新的致密的耐冲击的腐蚀产物膜,使合金元素向表在贩扩散过程得不到抑制,从而使双相黄铜的脱成分腐蚀不断被诱发,被加速,其中尤以β相连续的双相铜被加速的趋势最为明显,表面腐蚀产物膜分析表明,这两类铜合 腐蚀产物膜具备致密和耐冲击腐蚀的特征,在污染海水的情况下,由于硫离子等的作用,同时不能形成致密的腐蚀产物膜,同样使双相黄铜的腐蚀被逐年加速,由于这种污染元素的作用在试样露出水面时依然存在,致使潮差暴露也出现类似情况。     

Identification of zero-flux planes and flux reversals in several studies of ternary diffusion

Several past studies of isothermal diffusion in ternary systems have been examined for the identification of zero-flux planes (ZFP) and flux reversals of the individual components. The phenomenon of ZFP initially recognized in the Cu-Ni-Zn diffusion couples has now been identified in several ternary systems including Cu-Ag-Au, Cu-Zn-Sn, Fe-Ni-Co, Fe-Ni-Al, and Co-Ni-Cr. The development of ZFP is dictated by the terminal alloys of the diffusion couples and can occur in both single phase and multiphase assemblies. Discontinuous flux reversals can also occur at interfaces in multiphase systems. The compositions of ZFP’s developed for a couple correspond to the intersections of its diffusion path and the isoactivity lines for the components drawn through the terminal alloy compositions on a ternary isotherm.     

Diffusion structures in multiphase Cu-Ni-Zn couples

Isothermal, multiphase diffusion was investigated with infinite diffusion couples in the Cu-Ni-Zn system at 775°C. The couples were assembled with disks of a β (bcc) ternary alloy sandwiched between disks of selected binary, Cu-Ni α (fcc)alloys and were annealed for 2 hr to 2 days. The diffusion structures were investigated metallographically and by electron probe analysis. The couples developed multiphase structures that showed transitions from planar interfaces to nonplanar morphologies with changes in composition of the α -terminal alloys. The various structures are described by the aid of composition paths. The velocity of planar interfaces is discussed in terms of intrinsic fluxes in the adjacent phases. This paper is based upon a thesis submitted by R. D. SISSON, JR. to Purdue University in partial fulfillment of the requirements of the M.S. Metallurgical Engineering degree.     

Warm-temperature tensile ductility in Al−Mg alloys

Several binary and ternary Al alloys containing from 2.8 to 5.5 wt pct Mg were tested in tension at elevated temperatures (200°C to 500°C) over a range of strain rates (10⁻⁴ to 2.0 s⁻¹). Tensile ductilities of up to 325 pct were obtained in binary Al−Mg alloys with coarse grains deformed in the solute-drag creep regime. Under test conditions in which solute-drag creep controls deformation, Mg in concentrations from 2.8 to 5.5 wt pct neither affects tensile ductility nor influences strain-rate sensitivity or flow stress significantly. Strength is shown to increase with increasing Mg concentration, however, in the power-law-break down regime. The solute-drag creep process, which leads to superplastic-like elongations, is shown to have no observable grain-size dependence in a binary Al−Mg material. Ternary alloying additions of Mn and Zr are shown to decrease the strain-rate sensitivity during solute-drag creep, negatively influencing ductility. An important cause of reduced ductility in the ternary alloys during creep deformation is found to be a transition from necking-controlled failure in the binary alloys to cavitation-controlled failure in the ternary alloys investigated. An increase in ternary element concentration, which can increase the relative volume percentage of proeutectic products, increases cavitation.     

The prediction of the hydriding thermodynamics of Pd-Rh-Co ternary alloys

A dilute solution model (with respect to the substitutional alloying elements) has been utilized to accurately predict the hydride formation and decomposition thermodynamics and hydrogen storage capacities of dilute Pd-Rh-Co alloys. The effect of varying the rhodium and cobalt compositions on the thermodynamics of hydride formation and decomposition and hydrogen capacity of several palladiumrhodium-cobalt ternary alloys has been investigated using pressure-composition (PC) isotherms. Alloying in the dilute regime (<10 at. pct) causes the enthalpy for hydride formation to linearly decrease with increasing alloying content. Cobalt has a stronger effect on the reduction in enthalpy than rhodium for equivalent alloying amounts. Also, an increasing alloying content of cobalt reduces the hydrogen storage capacity. The plateau thermodynamics are strongly linked to the lattice parameters of the alloys. A near-linear dependence of the enthalpy of hydride formation on the lattice parameter was observed for both the binary Pd-Rh and Pd-Co alloys, as well as for the ternary Pd-Rh-Co alloys. The Pd-5Rh-3Co (at. pct) alloy was found to have similar plateau thermodynamics to a Pd-10Rh alloy; however, this ternary alloy had a diminshed hydrogen storage capacity relative to Pd-10Rh. This article is based on a presentation made at “The Milton Blander Symposium on Thermodynamic Predictions and Applications” at the TMS Annual Meeting in San Diego, California, on March 1–2, 1999, under the auspices of the TMS Extraction and Processing Division and the ASM Thermodynamics and Phase Equilibrium Committee.     

Evaluation of vanadium and vanadium-base alloys in hot-trapped sodium

Corrosion tests were conducted with vanadium-base alloys in zirconium-purified sodium from 450° to 750°C for 500 to 4000 hr. The materials tested were vanadium, binary vanadium alloys containing from 10 to 40 wt pct Ti, and two ternary alloys: V-5Ti-15Cr and V-15Ti-7.5Cr. The sodium was analyzed to contain from 1.7 to 8.7 ppm O by the vacuum-distillation technique. The behavior of these materials was determined from weight change data, and from chemical, metallographic, and electron-microprobe analyses of the test specimens. At temperatures up to 650°C, the maximum weight-change varied from a weight loss of 0.45 for vanadium to a weight gain of 0.46 mg per sq dm-day for the V-40Ti alloy. Chemical analyses of the corrosion test specimens indicated that vanadium-base materials were sensitive to the activity of oxygen, carbon, and/or nitrogen in sodium. Alloys containing >10 wt pct Ti increased in oxygen, carbon, and in some tests, nitrogen content, indicating that alloys of this titanium content are not compatible with sodium of the present purity. Complex titanium carbide precipitates were observed near the surface. V-5Ti-15Cr alloy was more resistant to liquid sodium than the other vanadium materials investigated.     

Thermodynamic Properties of Si - Mn - Y System Alloys

High-temperature isoperibolic calorimetry has been used to measure the partial enthalpies of mixing for yttrium in the Si - Mn - Y ternary system at 1775 K along sections with various atomic ratios of silicon to manganese (0.85/0.15; 0.7/0.3; 0.6/0.4; 0.5/0.5; 0.3/0.7) for yttrium concentrations in the range 0 < x_Y < 0.4 together with the partial molar enthalpies of manganese for x_Si/x_Y = 0.8/0.2. The integral enthalpies of mixing have been calculated from the partial ones for yttrium by Darken’s method. The addition of yttrium to the Si - M binary system to give the ternary Si - Mn - Y system increases the exothermic effects of the alloying substantially. There is a substantial effect on the thermodynamic parameters of the ternary alloys from the atomic interactions in the Si - Y and Si - Mn binary systems.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 64–69, March–April, 2005.     

Interrelation of TEM microstructure,composition, tensile properties,and corrosion resistance of Al-Cu-Mg-Mn alloys

Electron microscopy was used to investigate the effects of alloying element content and quenching rate on the extent of precipitation during quenching and the resulting type of corrosion attack of naturally aged Al-Cu-Mg-Mn, Al-Cu, Al-Cu-Mg and Al-Cu-Mn alloys. Magnesium addition to Al-Cu led to S-phase (Al₂CuMg) grain boundary precipitation and development of dislocation loops of the condensed vacancy type. This appears attributable to the greater affinity of magnesium atoms for copper atoms than for vacancies. Manganese, in the presence of copper and magnesium, retarded precipitation, apparently because of its high affinity for vacancies, lowering the number of unassociated vacancies available for long range diffusion. While increasing as-quenched strengths, this association apparently has the effect of developing grain boundary regions with steep electrochemical potential gradients, which appear responsible for susceptibility of the alloy to intergranular corrosion. It is concluded that precipitation phenomena which control the hardening and corrosion behavior of these alloys are related to the relative binding energies between the several solute elements, the affinities of these individual elements for vacancies, and the ratio of the atomic concentrations of the solute elements.     

含Cu镁锂合金组织与性能调控研究进展

镁锂合金具有超低密度、极高的比强度与比刚度、优异的电磁屏蔽性能及阻尼性能,目前广泛应用于追求轻量化的航空航天、新能源汽车、电子产品、生物医疗等领域。由于合金元素镁和锂均为活泼金属,在服役过程中镁锂合金会存在多种形式的腐蚀过程,同时二元镁锂合金强度较低,以上两点严重制约了其广泛应用。耐蚀涂层可以有效提高镁锂合金的腐蚀抗力,含铜镀层被证实能够提升镁锂合金耐蚀性。改善镁锂合金强度的工艺主要有合金化、热处理、加工变形等,其中合金化是最基本的强化手段。Cu合金化可以对镁锂合金中的组织与性能进行调控,改善镁锂合金的强度。本文对含Cu镁锂合金的研究进展及其应用情况进行综述,总结了目前含Cu镁锂合金耐蚀与力学性能的相关研究成果,重点梳理了铜元素在镁锂合金中的作用,为含Cu镁锂合金的实际应用提供一定的理论指导。