Electrodeposition of Rare Earth Metals and Their Alloys

ＥｌｅｃｔｒｏｄｅｐｏｓｉｔｉｏｎｏｆＲａｒｅＥａｒｔｈＭｅｔａｌｓａｎｄＴｈｅｉｒＡｌｌｏｙｓＹａｎｇＱｉｑｉｎ，ＬｉｕＧｕａｎｋｕｎ，ＴｏｎｇＹｅｘｉａｎｇ，ＡｏＹａｎｂｉｎｇａｎｄＳｕＹｕｚｈｉ（杨绮琴）（刘冠昆）（童叶翔）（敖炎兵）（苏育志）...     

High Temperature Corrosion and Protection of Titanium Alloys and TiAl Intermetallics

ＨｉｇｈＴｅｍｐｅｒａｔｕｒｅＣｏｒｒｏｓｉｏｎａｎｄＰｒｏｔｅｃｔｉｏｎｏｆＴｉｔａｎｉｕｍＡｌｌｏｙｓａｎｄＴｉＡｌＩｎｔｅｒｍｅｔａｌｌｉｃｓＴａｎｇＺｈａｏｌｉｎ；ＷａｎｇＦｕｈｕｉａｎｄＷｕＷｅｉｔａｏ（唐兆麟）（王福会）（吴维）（Ｓｔａｔ...     

Status of Applications of Rare Earth Metals to Precision Alloys

1.IntroductionRare earth resources in China are the most abundant with more than twenty factories pro-ducing rare earths in the country,the production capability ranks second in the world.At present,steels added with rare earths have production scale in China's metallurgical indus-try,such as steels for gears,bearings,springs,bridges,automobile beams,ploughshares heating al-     

Description and Prediction of the Solid Solubilities of Binary Alloys Based on the Actinide Metals

The solid solubilities of 207 binary alloys based on the three actinide metals (Th, U and Pu) at room tem-perature are studied with the two theoretical schemes suggested by one of the present authors (ZBW).The re-sults show that the soluble elements can be distinguished from the insoluble ones by a parabola y_1=a--bx~2 oran ellipse (x_2,-m)~2/c~2+(y_2-n)~2/d~2=l with the total reliabilities of 87.9% and 92.3% respectively for the 207binary alloys. The contants a and b in the parabola equation, and c, d, m and n in the ellipse equation can berelated to some appropriate parameters for each host metal respectively. The reasons are discussed. From thetheories the soluble elements in these actinide host metals that have not been measured yet can be predicted inthe accuracies of the schemes.     

Wettability of Monocrystalline Silicon Carbide by Molten Metals and Binary Metal－Silicon Alloys

ＷｅｔｔａｂｉｌｉｔｙｏｆＭｏｎｏｃｒｙｓｔａｌｌｉｎｅＳｉｌｉｃｏｎＣａｒｂｉｄｅｂｙＭｏｌｔｅｎＭｅｔａｌｓａｎｄＢｉｎａｒｙＭｅｔａｌ－ＳｉｌｉｃｏｎＡｌｌｏｙｓＬｉＪｉａｎ’ｇｕｏ（李建国）（ＩｎｓｔｉｔｕｔｆｕｒＮｉｃｈｔｍｅｔａｌｌｉｓｃ...     

Review on ω Phase in Body-Centered Cubic Metals and Alloys

An to phase with a primitive hexagonal crystal structure has been found to be a common metastable phase in body-centered cubic(bcc) metals and alloys.In general,to phase precipitates out as a high density of nanoscale particles and can obviously strengthen the alloys;however,coarsening of the co particles significantly reduces the alloy ductility.The co phase has coherent interfacial structure with its bcc matrix phase,and its lattice parameters are a_ω =2~(1/2)×a_(bcc) and C_ω= 3~(1/2)/2 ×a_(bcc).The common {112}(11 l)-type twinning in bcc metals and alloys can be treated as the product of theω→ bcc phase transition,also known as the ω-lattice mechanism.The ω phase's behavior in metastable β-type Ti alloys will be briefly reviewed first since the ω phase was first found in the alloy system,and then the existence of the ω phase in carbon steels will be discussed.Carbon plays a crucial role in promoting the ω formation in steel,and the ω phase can form a solid solution with various carbon contents.Hence,the martensitic substructure can be treated as an α-Fe matrix embedded with a high density of nanoscale ω-Fe particles enriched with carbon.The recognition of the ω phase in steel is expected to advance the understanding of the relationship between the microstructure and mechanical properties in bcc steels,as well as the behavior of martensitic transformations,twinning formation,and martensitic substructure.     

Corrosion Behavior of Copper–Nickel Alloys in Neutral Chloride and Sulfide Containing Solutions

The corrosion behavior of Cu30Ni and 30-1-1 alloys in oxygen-containing chloride solutions (0.1–0.5 N NaCl) with and without Na₂S additive (2–1000 mg/l) is studied with radiometric and electrochemical methods by taking into account the amount of oxygen sorbed in the course of corrosion. In blank solutions, a film of corrosion products is formed on the alloy surface; the thickness and copper content of the film increase with a decrease in chloride concentration. The corrosion rate in sulfide-containing solutions is higher than in sulfide-free ones. In the initial corrosion period, nickel compounds are accumulated in the film. With an increase in sodium sulfide concentration, corrosion accelerates. Additionally alloying the Cu30Ni alloy with manganese and iron reduces its rate by half.     

Galvanic Series of Metals and Effect of Alloy Compositions on Corrosion Resistance in Sanya SeawaterEI北大核心CSCD

With the development of ocean engineering, various metallic materials have been applied to the marine environment. It is an urgent requirement to study the galvanic series and alloy composition optimization of metallic materials in the tropical marine environment. In this work, open circuit potentials (OCP) and galvanic series of 36 kinds of metallic materials in Sanya seawater were studied. By considering the response of OCP to tidal changes, the anti-corrosion effects of alloying elements were also ana lyzed. The results show that the OCP of metallic materials in Sanya seawater has a large range. The galvanic series order of metallic materials from high to low in Sanya seawater is: nickel alloy, duplex stainless steel, austenitic stainless steel and pure copper, ferritic stainless steel, martensitic stainless steel, copper alloy, low alloy steel, carbon steel, cast iron, aluminum alloy and aluminum anode. Low-carbon high-alloy content carbon steel and high Cr, Ni contents stainless steel have higher OCP. The potential fluctuations of carbon steel with tidal changes involves two phases: (1) under the dynamics control, the OCP of carbon steel is more negative at high tide; (2) under the diffusion control, the OCP is more positive at high tide. The potential fluctuations of metallic materials reflect the effect of the corrosion product film on the change of ionization balance, and metals with less potential fluctuations have better inhibition on ion diffusion. In Sanya seawater, the carbon steel, which has more alloying content and less carbon content, has less potential fluctuations with the tidal changes and has good oxygen diffusion resistance. The potential fluctuations of austenitic stainless steel with tidal changes are less than that of ferritic stainless steel and martensitic stainless steel. After 2700 h immersion, austenitic stainless steel and martensitic stainless steel, which have a higher content of Mo, have more stable OCP. In other words, the corrosion film gets a better corrosion resistance. The OCP of aluminum anode in Sanya seawater environment increases when the oxygen content is brought up. The OCP of Zn-containing or Ga-containing aluminum anode remains relatively stable. Al bronze and T2 copper have less potential fluctuations with tidal changes, and perform good corrosion resistance in Sanya seawater.     

Microstructure and Tensile/Corrosion Properties Relationships of Directionally Solidified Al–Cu–Ni Alloys

Al–Cu–Ni alloys are of scientific and technological interest due to high strength/high temperature applications, based on the reinforcement originated from the interaction between the Al-rich phase and intermetallic composites. The nature, morphology, size, volume fraction and dispersion of IMCs particles throughout the Al-rich matrix are important factors determining the resulting mechanical and chemical properties. The present work aims to evaluate the effect of the addition of 1wt%Ni into Al–5wt%Cu and Al–15wt%Cu alloys on the solidification rate, macrosegregation, microstructure features and the interrelations of such characteristics on tensile and corrosion properties. A directional solidification technique is used permitting a wide range of microstructural scales to be examined. Experimental growth laws relating the primary and secondary dendritic spacings to growth rate and solidification cooling rate are proposed, and Hall–Petch type equations are derived relating the ultimate tensile strength and elongation to the primary dendritic spacing. Considering a compromise between ultimate tensile strength and corrosion resistance of the examined alloys samples from both alloys castings it is shown that the samples having more refined microstructures are associated with the highest values of such properties.     

Oxidation of Pd and Pd-RE Alloys

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High-Temperature Corrosion of Iron–Chromium Alloys in Oxidizing–Chloridizing Conditions

An investigation has been carried out into the effects of 0.1 to 1.0% HCl onthe oxidation of Fe–28%Cr and Fe–28%Cr–1%Y inargon–20%O₂ at 600 and 700°C. At the higher temperature,the additions of HCl to the gas caused considerable increases in corrosionof the binary alloy, with the rates of metal loss actually being greaterthan those of iron in the 0.5 and 1% HCl-containing environments. Thick andmultilayered scales were observed; these were oxides, particularlyFeCr₂O₄ and Fe₂O₃, that developedfollowing formation and vapor phase transport of chlorine-containing speciesfrom the metal surface. The main metal-loss processes were evaporation ofFeCl₂, CrCl₂, and CrO₂Cl₂, withthe first two of these reacting with oxygen to form solid oxides in thescale, while the third was lost mainly to the environment. The addition of1% Y to the alloy resulted in a marked improvement in corrosion resistanceat 700°C, because of the reactive element facilitating rapidestablishment of a protective Cr₂O₃-rich layer andpromoting the formation of condensed chlorides rather than the more volatileCrO₂Cl₂ phase. At 600°C, additions of HCl toargon–20%O₂ caused formation of some localized condensedchlorides on both alloys, but the corrosion rates were relatively low,because of protection by a Cr₂O₃-rich oxide scale.     

Hot Corrosion of Ti–Re Alloys Fabricated by Selective Laser Melting

Selective laser melting (SLM) is an additive manufacturing process that enables novel alloy production by combining metals with significantly different physical properties. In this paper, the hot corrosion behavior of Ti–Re alloys fabricated by SLM was studied in a mixture of Na₂SO₄ and NaCl salts at 600 °C. The morphology and composition of the corrosion products were characterized by scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction to understand the degradation mechanisms. It has been shown that the hot corrosion resistance of Ti–Re alloys was influenced by the chemical inhomogeneity of the oxide scale resulting from the presence of rhenium particles undissolved during the SLM process.     

Pitting Corrosion in Copper Tubes – Cause of Corrosion and Counter-Measures

Abstract

An investigation of failures of hard-drawn copper water pipes (phosphorus-deoxidised copper) in service due to pitting corrosion was conducted from November, 1962 to February, 1965. Fifteen cases were reported. All those about which information could be obtained came from hot water installations and occurred in water with a low pH (≤7) and a HCO_3- content of, at the most, 100 mg/l but generally below 50 mg/1. Failures not due to pitting corrosion (i.e. caused by erosion and corrosion or corrosion fatigue) occurred in waters with a higher pH and higher HCO₃- content.

A laboratory investigation into the ability of the corrosion products to counteract further corrosion in different types of water was also carried out, using an electrolytic cell which, in principle, was a model of an active pit in a copper tube. This led to the following conclusions, which are in good agreement with the results obtained from the examination of service failures:

If the pH value of the water is high enough, the copper dissolved by the corrosion can be precipitated as basic copper salt. At low pH values such precipitation does not take place.

If the [HCO₃^?]/[SO₄^2?] ratio in the water is high, dissolved copper can be precipitated as basic copper carbonate in the neighbourhood of the corrosion site and counteract further corrosion.

At a low [HCO₃^?]/[SO₄^2?] ratio, crusts of basic copper sulphate will be precipitated at some distance from the corrosion site and may lead to a high corrosion rate.

Pitting is not likely to occur in hot water tubes of hard copper if the pH is ≥ 7·4 and the [HCO₃^?]/[SO₄^2?] ratio ≥1 (the concentrations given in mg/1). The critical values mentioned are approximate and may be adjusted in the light of future experience.     

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.     

Corrosion behavior of magnesium and magnesium alloys

The automotive industry has crossed the threshold from using magnesium alloys in interior applications such as instrument panels and steering wheels to unprotected environment such as oil pan, cylinder head and wheels. The expanding territory of magnesium leads to new challenges.mainly environmental degradation of the alloys used and how they can be protected. The present critical review is aimed at understanding the corrosion behavior of magnesium and magnesium alloys in industrial and marine environments, and the effect of microstructure, additive elements and inhibitors on the corrosion mechanism.     

Effect of Sub-T_g Annealing on the Corrosion Resistance of the Cu–Zr Amorphous Alloys

Despite the economy of material cost and excellent toughness of Cu-based amorphous alloys, especially Cu_(50)Zr_(50), their poor corrosion resistance to a chloride medium limits their widespread applications. In this study, corrosion tests were performed on the Cu_(50)Zr_(50) amorphous alloy with different degrees of short-range order, which were prepared by annealing below the glass transition temperature(T_g). It was found that the corrosion resistance of amorphous alloys is improved to a significant level when the alloys were heated below T_g. Calorimetric studies showed that thermally activated relaxation process of created disorder, which occurs during sub-T_gannealing, is responsible for the improvement in the corrosion resistance. Molecular dynamics simulations performed on the Cu–Zr amorphous alloys demonstrated that the relaxation process of the alloys is associated with the formation of energetically stable icosahedra and icosahedron-like structures. Our study highlights the effects of sub-T_gannealing on the improvement in the corrosion resistance of the amorphous alloys from the viewpoint the relaxation process of the short-range orders.     

Microstructure,Mechanical Properties and Corrosion Behavior of Extruded Mg–Zn–Ag Alloys with Single-Phase Structure

Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag(wt%,x=0.2,0.5 and0.8)alloys with single-phase crystal structure were prepared by backward extrusion at 340°C.The addition of Ag element into Mg–3Zn slightly influences the ultimate tensile strength and microstructure,but the elongation firstly increases from12%to 19.8%and then decreases from 19.8%to 9.9%with the increment of Ag concentration.The tensile yield strength,ultimate tensile strength and elongation of Mg–3Zn–0.2Ag alloy reach up to 142,234 MPa and 19.8%,respectively,which are the best mechanical performance of Mg–Zn–Ag alloys in the present work.The extruded Mg–3Zn–0.2Ag alloy also possesses the best corrosion behavior with the corresponding corrosion rate of 3.2 mm/year in immersion test,which could be explained by the single-phase and uniformly distributed grain structure,and the fewer twinning.     

Dissolution Behaviour and Electrodeposition of Strontium and its Alloys

The electromotive force(EMF)was determined by electrochemical method at 760～950℃ for the concen-tration cell:(Mo)Sr|SrCl_2,--Sr sat.||SrCl_2,--xSr|Mo. The dissolution behavior of Sr and alloyed strontium(i.e.Cu--Sr or Al--Sr) in molten salt containing SrCl_2 was studied. The electrolysis of SrCl_2 for production ofSr and its alloys(Al-Sr and Cu-Sr) was also conducted on the basis of electrochemical measurement. The disso-lution data so obtained well agree with the results from phase diagram.     

Effect of Mn Modification on the Corrosion Susceptibility of Mg–Mn Alloys by Magnesium Scrap

The microstructure and anti-corrosion behavior of Mg–Mn alloys by magnesium scrap have been investigated in this study.The results show that the size of the Fe-rich particles in magnesium scrap decreases but the quantity increases with the Mn addition.Although the presence of Mn-containing Fe-rich particles with unique symbiotic structure can eff ectively weaken the micro-galvanic corrosion,the presence of more free Fe(Fe-rich particles) does not necessarily lead to severe corrosion of the alloy.The corrosion susceptibility of Mg–Mn–Fe alloy primarily depends on the solubility of iron in the Mg matrix,while it can be significantly reduced by suitable Mn addition.Besides,the tolerance limit of the Fe impurity can be expressed as Fe_(max) = 0.0083 Mn(relative to the iron solubility).Only when the Fe/Mn ratio is below 0.0083 can the alloy have excellent corrosion resistance,with the corrosion rate changing in the scope of 0.38 ± 0.09 to 0.54 ± 0.15 mg/cm~2 day and i_(corr) from 3 to 9 × 10~(–4) A/cm~2.