铂族金属高温固溶强化型合金

讨论了高温固溶强化机制和合金元素对Pt固溶强化效应.介绍了铂族金属和Pt-Rh、Pt-Ir和Pt-Pd-Rh固溶型合金的的高温力学性能.借助不同的强化机制,在Pt-Rh或Pt-Pd-Rh合金中添加少量Ir、Ru、Mo、Au等组元,或微量稀有金属Zr、Hf或稀土金属,可以提高合金的高温强度性质和改善抗蠕变能力.     

Influence of gd addition on the structure and properties of Au-Ni and Au?Ni?Cr alloys

The influence of Gd additions on the microstructure and properties of Au-Ni and Au-Ni-Cr alloys are reported. The alloys remain single phase solid solution at Gd contents of −0.1wt%, but at contents τ 0.1%, two phases structures are formed, consisting of (Au) and a low melting point intermetallic compound containing Gd. Trace additions of Gd refine the grain size, increase strength and the recrystallization temperature, but without detriment to the good electric conductivity of these alloys. The wear life of potentiometer windings made of gold alloys containing Gd are at least one order of magnitude higher than those made in the Gd-free gold alloys. The design of gold alloys for precise electrical contact and resistance materials by conventional and microalloying is discussed.     

Modification of Al-Si alloys: Microstructure,thermal analysis,and mechanisms

In aluminum-silicon cast alloys, the shapes of the silicon phase and the general solidification pattern can be changed by the cooling conditions and by minor additions to the melt. The minor additions either cause modification (sodium, strontium, and other metals) or refine the primary silicon in hypereutectic alloys (phosphorus and elements of Group V-B). Detailed examination of the modified microstructures and analysis of cooling curves are compatible with a modification mechanism involving growth rather than nucleation kinetics.     

A.C. anodizing of aluminium alloys

Three age-hardening aluminium alloys were compared with aluminium of commercial purity in terms of their susceptibility to anodization in an alternating current in 10% sulphuric acid at 35 V. Modifying additions of nitric acid and sodium sulphate were used to increase the rate of film growth. The former was relatively ineffective and the latter was very effective but vielded soft highly porous films. Neither is considered to be ideal in the context of functional engineering anodized surfaces.     

贵金属在船用钛及钛合金表面改性中的应用

舰船用钛及钛合金耐磨性较差,在海水中会被腐蚀,贵金属表面改性剂可以改善其耐磨性,提高耐腐蚀能力。基于钛及钛合金性能特点的分析,综述了贵金属金和银在改善耐磨性,钯、钌、银和金在增强耐腐蚀能力方面的应用,介绍了离子注入、磁控溅射、双层辉光等离子技术等贵金属表面改性工艺,对改性层复合化、纳米化的发展趋势进行了分析。     

Effect of Hot-Rolling on Microstructures and Mechanical Properties of Extruded Mg-6Gd-3.2Y-xZn-0.5Zr Sheet

The optical microscope (OM), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), x-ray diffractometer (XRD), x-ray energy spectrometer, Vickers hardness tester, and universal tensile test machine were employed to investigate the effects of Zn additions and hot-rolling on microstructures, aging behaviors, and mechanical properties of Mg-6Gd-3.2Y-0.5Zr extruded sheet. Block-shaped and acicular LPSO structures are found in the alloy containing Zn. The block-shaped LPSO structures can refine the microstructure and improve the secondary deforming ability. The size of β′ phases between the acicular LPSO structures decreases greatly. Both the block-shaped and acicular LPSO structures can improve the tensile mechanical properties of the Mg-Gd-Y-Zn-Zr alloys. Secondary deformation which gives rise to residual stress can promote age-hardening behavior and shrinks the peak-aging time. Owing to LPSO structures and the secondary deformation, T10 sample of alloy C obtains the highest proof strength of 375 MPa and tensile strength of 420 MPa.     

定向凝固含Y镁合金的枝晶形态及微观组织研究

采用液态金属冷却高温度梯度定向凝固炉制备了含稀土元素Y的镁合金,研究了定向凝固镁合金的枝晶形态及微观组织特征。结果表明,镁合金的一次枝晶沿着热流方向生长,且一次枝晶周围含有六个二次枝晶呈花瓣形状。通过扫描电镜及能谱分析发现,凝固组织中除了a(Mg)固溶体及枝晶间的?(Mg17Al12)相组成外,还存在稀土相。稀土相呈粗大的杆状和细小的粒状形态,主要由Y、Mg、Al和Mn元素组成,其中稀土Y的质量分数占22%左右。     

Transition Element Modifications of Al-Li

The development of aluminum-lithium metallurgy has led to alloys with unsurpassed combinations of density, specific strength, and specific modulus. This paper describes recent advances in the modification of aluminum-lithium binary alloys through additions of the Group IV-A transition metals (titanium, zirconium and hafnium). These elements lead to a duplex precipitation hardening behavior through the formation ofAlJLi and Al₃(TM,Li) (TM = transition element) which act as strengthening precipitates. The influence of the duplex structure on deformation mechanisms and the improvement of mechanical properties in these systems is illustrated by using results for the Al-Li-Zr system.     

铜镍合金氯化渣富集贵金属

针对含贵金属０．１２％的高冰镍磨浮磁选铜合金氯化浸出渣富集贵金属生产流程中的不足,提出了新的工艺流程结构,包括煤油脱除元素硫－熔炼含贵金属高锍－加压酸浸三个步骤,贱金属分离效率（％）：Ｃｕ９９．５、Ｎｉ９９．８、Ｆｅ９４．５、Ｓ９９．６、ＳｉＯ２９８．８;贵金属回收率（％）：Ｐｔ９８．０、Ｐｄ９７．０、Ａｕ９７．０,产出贵金属品位〉３０％,贵贱比〉１的精矿。     

Microstructure evolution and age-hardening response in Mg-Sn-Sm alloys under a wide range of Sm/Sn ratio

The microstructure evolution and age-hardening response for different Sm/Sn ratios (0–2.55, in wt.%) of Mg-Sn-Sm alloys were investigated. The second phase formation in as-cast alloys and the Mg₃Sm precipitates formed in aged alloys were characterized using XRD, FESEM and HAADF-STEM with EDS techniques. Results indicate that the Sm/Sn ratio has a great influence on the phase constitution, α-Mg grain size and age-hardening response. With the increment of Sm/Sn ratio, Mg₄₁Sm₅ and thermally stable MgSnSm phases precipitate. When the Sm/Sn ratio is about 1.19, the secondary dendrite arm spacing of α-Mg grains significantly decreases. Furthermore, the alloy with Sm/Sn ratio up to 2.55 exhibits the highest age-hardening response, the hardness value increases from 52 HB at solution-treated condition to 74 HB at peak-aged condition (ageing at 220 °C for a short time of 4 h). This is attributed to the large volume fraction of needle-like Mg₃Sm precipitates formed in the α-Mg matrix during ageing treatment, which results in a significant precipitation strengthening effect.

     

Characterization and growth of oxide films

Surface-analytical techniques are useful to characterize oxide films and to study growth processes on metals and semiconductors. This paper will summarize work at the National Research Council of Canada on the high temperature oxidation of nickel, chromium, FeCrAl alloys (with and without yttrium additions), β-NiAl and silicon. The application of secondary ion mass spectrometry, reflection high energy electron diffraction, and transmission electron microscopy is emphasized. Also considered is the thermal oxidation of III-V semiconductors, indium phosphide and gallium arsenide. X-ray photoelectron spectroscopy provides additional useful information on the chemical composition of the oxides. The often complementary information provided by the various techniques leads to (i) a better understanding of oxidation processes and of oxide growth mechanisms on an atomic scale, (ii) interfacial segregation phenomena, and (iii) the role of reactive elements like yttrium in modifying transport processes in oxides.     

Progress in the design of sulphidation-resistant alloys

The interaction of metallic materials with sulphur and sulphur-bearing gases at elevated temperatures leading to the formation of sulphide corrosion products, sulphidation, is generally an extremely rapid process, much more so than oxidation. Conveniently-developed high-temperature alloys with adequate oxidation performance generally have poor resistance to sulphidation and the design of alloys or coatings to withstand such aggressive environments represents a major technological challenge. The principles underlying the development of sulphidation resistance in alloys via selective attack of specific alloying additions to promote the formation of barrier layer protective sulphides are reviewed. The actual limited efficiency of additions of elements such as Cr and Al to Fe, Ni or Co is illustrated. The prospects in the use of other Group IV-VI semi-refractory and refractory addition elements are discussed and the greatly enhanced performance of various experimental alloys containing these metals is illustrated and interpreted. Future research areas are indicated.     

Electrochemical assessment of the tarnish resistance of decorative gold alloys

Electrochemical methods were investigated to assess the tarnish resistance of typical gold alloys used mainly for decorative purposes. Three mechanically clad alloys (14 and 18 carats (ct) Au-Ag-Cu and 14 ct Au-Ag-Cu-Zn) and three electroplated coatings (18 ct Au-Cu-Cd, 22 ct Au-Ni and 22 ct Au-Ni plus a flash layer for colour matching) were studied. Potentiostatic, cyclic constant-current chronopotentiometric and coulometric measurements were carried out in 1 N NaOH containing between 10^-5 and 0.26 M Na₂S. The electrochemical data were compared with the results obtained from liquid-based and vapour-phase chemical tests by means of colorimetric measurements and the data were expressed in the Commission Internationale de l'Eclairage (CIE) 1976 L¹a¹b¹ colour space. The electrochemical measurements showed that the sulphidation of non-noble metals of the gold alloys occurred in parallel with the oxidation of sulphide ions. Only the first reactions contributed to tarnish by producing insoluble, adherent and coloured sulphide films, while the oxidation of sulphide led to mainly colourless and non-adherent species. The current density measured at a properly chosen potential of the potentiostatic scan correlated with the non-noble metal content of the alloy. The cathodic charge determined by chronopotentiometry provided an excellent indication of the extent of sulphidation of a given alloy. The results of these electrochemical techniques were in good agreement with the data obtained from chemical tests. The thickness of the tarnished films as determined by cathodic reduction in 1 N NaOH was smaller than 100 Å assuming a silver sulphide coverage of unity. The potential value and length of the arrest in the potential vs. time curve gave interesting qualitative and quantitative information on the chemical composition of the tarnished films.     

Physical properties of selected brazing filler metals

Abstract

A suitable selection of the filler metal is vital for producing satisfactory brazed joints. The wettability of brazing alloys with base metals depends on physical properties such as surface tension, density, melting point, and viscosity. Thermal conductivity and electrical resistivity are also important since the filler metal is frequently required to have similar values to those of the base metal. In the present paper, the physical properties of liquid alloys relevant to brazing have been evaluated. Six different filler metal systems were analysed, comprising alloys based on Ag, Al, Au, Cu, Ni, and Ti. Results show that the viscosity values for most binary brazing filler alloys are of the order of 2–8 mPa s, with Cu and Al alloys exhibiting the lowest viscosities. The surface tensions of brazing alloys vary from 800 to 1800 mN m^-1, with the lowest surface tension values corresponding to the Ag and Al alloys. Thermal conductivity and electrical resistivity values fall in the range 10–200 W m^-1 K^-1 and 17–300 μΩ cm, respectively.     

Effects of indium addition to CuAu alloy on phase transformation behaviors

The effects of indium addition to CuAu on the alloy phase transformation behavior were investigated by hardness tests, electrical resistivity measurements, X-ray diffraction and transmission electron microscopy. These established that indium additions lower the critical temperature and stabilize the CuAu II phase at room temperature. Formation of the long period ordered phase produces an age-hardening; although this age-hardening is retarded, the degree of hardening is comparable to that in CuAu. It was noted that the axial ratio increases and the antiphase domain size decreases.     

Phase Characteristics of a U-22Pu-4Am-2Np-40Zr Metallic Alloy Containing Rare Earths

Metallic fuel alloys consisting of uranium (U), plutonium (Pu), and zirconium (Zr) with minor additions of americium (Am) and neptunium (Np) are under evaluation for potential use to transmute long-lived transuranic actinide isotopes in fast reactors. The current irradiation test series design, designated Advanced Fuel Cycle-2 (AFC2), includes minor additions of rare earth (RE) elements to simulate expected fission product carryover from the electrochemical molten salt reprocessing technique. The as-cast fuel alloys have been investigated for phase and thermal properties; specifically, enthalpies of transition, transition temperatures, and room temperature phase characteristics. Results and observations related to these characteristics for the “fresh” fuel alloys are provided. The alloy compositions are based on a U-22Pu-4Am-2Np-40Zr alloy, along with additions of 1.3 and 1.9 at.% RE (at the expense of uranium where RE denotes rare earth alloy of cerium, lanthanum, praseodymium, and neodymium). Phase behavior and associated transitions have been compared to available U-Pu-Zr ternary diagrams with acceptable agreement. Enthalpies of transition were deconvoluted from heating and cooling thermal traces for relatively reliable values. The RE additions to the base alloy have a minimal influence on the room temperature phases present and phase transition temperatures, but the room temperature phases present did impact the enthalpies of transition.     

Influence of Silicon and Aluminum Additions on the Oxidation Resistance of a Lean-Chromium Stainless Steel

The effect of Si and Al additions on the oxidation of austenitic stainless steels with a baseline composition of Fe–16Cr–16Ni–2Mn–1Mo (wt.%) has been studied. The combined Si and Al content of the alloys did not exceed 5 wt.%. Cyclic-oxidation tests were carried out in air at 700 and 800°C for a duration of 1000 hr. For comparison, conventional 18Cr–8Ni type-304 stainless steel specimens were also tested. The results showed that at 700°C, alloys containing Al and Si, and alloys with only Si additions showed weight gains about one half that of the conventional type-304 alloy. At 800°C, alloys that contained both Al and Si additions showed weight gains approximately two times greater than the type-304 alloy. However, alloys containing only Si additions showed weight gains four times less than the 304 stainless. Further, alloys with only Si additions preoxidized at 800°C, showed zero weight gain in subsequent testing for 1000 hr at 700°C. Clearly, the oxide-scale formation and rate-controlling mechanisms in the alloys with combined Si and Al additions at 800°C were different than the alloys with Si only. ESCA, SEM, and a bromide-etching technique were used to analyze the chemistry of the oxide films and the oxide–base-metal interface, in order to study the different oxide film-formation mechanisms in these alloys.     

STRENGTH-DUCTILITY AND γ'PRECIPITATES IN Ni-BASE ALLOYS

ＳＴＲＥＮＧＴＨ－ＤＵＣＴＩＬＩＴＹＡＮＤγ＇ＰＲＥＣＩＰＩＴＡＴＥＳＩＮＮｉ－ＢＡＳＥＡＬＬＯＹＳ￥ＷＡＮＧＺｈｉｘｉｎｇ;ＸＩＥＳｈｉｓｈｕ;ＬＵＪｕｎｙｉｎｇ;ＷＡＮＧＬｅｉ;ＹＡＮＧＨｏｎｇｃａｉ（ＮｏｒｔｈｅａｓｔｅｒｎＵｎｉｖｅｒｓｉｔｙ...     

Vergleichende Untersuchung der Schweißzusätze Alloy C22 und Alloy 59 Zur Frage der Einsetzbarkeit des Schweißzusatzes Alloy 59 für das Schweißen von Nickellegierungen der C‐Reihe bei Anwendungen in der chemischen Prozessindustrie

A comparative investigation of weld filler materials Alloy C22 and Alloy 59 In the chemicals processing industry all nickel alloys of the C series are utilised in vessels and pipelines. Due to ever increasing corrosion demands these materials are being replaced by higher alloys such as Alloy 59. The present research aims to establish whether all available base metals can be welded with a filler material such as Alloy 59.     

ENERGY DISTRIBUTION OF BACKSCATTERED ELECTRONS FROM HEAVY METALS

The full energy distribution of backscattered electrons from the elastic peak down to the true-secondaty electron peak for heavy metals, Ta, W, Pt and Au, in Auger electron spectroscopy in the EN(E) mode has been studied with a Monte Carlo simulation method, which includes cascade-secondary-electron production. The simulation model is based on the use of a dielectric function for describing inelastic scattering and secondary excitation, and on the use of Mott cross sections for elastic scattering. A systematic comparison between the calculated and experimental spectra measured with a cylindrical mirror analyzer has been made for primary energies ranging from 1 to 5keV. Excellent agreement was obtained for these heavy metals on the backscattering background at primary energies in the keV region. A significant contribution of cascade secondary electrons to the measured spectra on the low-energy side was found.