氯化镧对2024铝合金缝隙腐蚀的缓蚀作用

为了降低2024铝合金在海水中的缝隙腐蚀敏感性,采用浸泡和动电位极化、电化学阻抗等研究了氯化镧(LaCl₃)对该铝合金缝隙腐蚀行为的影响,并通过原子力显微镜对缝隙试样内、外腐蚀产物膜的形貌进行了观察.结果表明:当海水中LaCl₃的质量浓度超过2.0 g·L^-1以后,它能有效地减缓2024铝合金在海水中的缝隙腐蚀.这主要是因为LaCl₃减缓了缝隙的阴极反应速率,降低了缝隙内、外的氧浓度差,且缝隙内、外生成的均匀致密的腐蚀产物膜降低了Cl-侵蚀性,这些因素抑制了缝隙的萌生与扩展,提高了2024铝合金在海水中的抗缝隙腐蚀能力.     

High voltage metallography of stress corrosion failure in a Ni-16.5 At. Pct Au alloy

The same portion of a stress corrosion crack in a Ni-16.5 at. pct Au alloy was examined by light microscopy and in the electron microscope at 800 and 100 kv. It was observed that the fracture propagates through a mechanically weak corrosion sponge which nucleates at slip steps created during exposure to the stress corrosion environment. The sponge is composed of a high density of branching corrosion tunnels with an average diameter of 70 to 90Å and containing small particles of gold. A mechanism is proposed to account for the stability of corrosion tunnels in alloys whose components dissolve at different rates and it is predicted that under certain conditions corrosion crevices may become stable. No cracks were observed to propagate beyond the corrosion sponge into the unattacked alloy.     

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg-5Zn-0.3Zr alloys behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. The additions of Nd and Y into Mg-5Zn-0.3Zr alloy also improve the compactness of the corrosion product film and are beneficial to the corrosion resistance.     

Influence of carbon content and ferrite morphology on the sensitization of duplex stainless steel

The influence of ferrite morphology and carbon content on the intergranular corrosion behavior of 308 stainless steel was investigated using four wrought alloys and six weld deposited alloys. The four wrought alloys were heat treated at four different annealing temperatures to introduce four different amounts of ferrite. The annealed samples along with the weld deposited alloys were aged at temperatures ranging from 480 to 700°C for times varying between 15 min and 1000 h and then tested for intergranular corrosion susceptibility in acidified copper-copper sulfate solution. For a given carbon content there exists a critical amount and distribution of α-γ boundary area above which the alloy is immune and below which it is susceptible to intergranular corrosion. For amounts and distributions of α-γ boundary area less than the critical value two types of sensitization behavior are possible. First, there may be a sufficient amount and distribution of α-γ boundary area to insure rapid healing of the sensitized microstructure. Second, there may be an inadequate amount or distribution of α-γ boundary area to produce either immunity or rapid healing and the alloy behaves as a fully austenitic alloy regardless of the amount of ferrite present. A model is presented which describes as a function of carbon content the critical amounts and distributions of α-γ boundary area required for rapid healing and immunity to sensitization.     

铝锂合金材料研究应用现状与展望

铝锂合金是一类具有广阔应用前景的航空航天结构材料，已经历经90余年的发展历程.从铝锂合金的研发、生产和应用角度看，我国与国外仍存有不小差距.按成型方式铝锂合金可分为变形和铸造2大类, 目前研究较多和广泛应用的是变形铝锂合金.文中从析出相、热处理、腐蚀性和焊接性等方面介绍了变形铝锂合金的研究现状.同时从发展应用以及合金开发等方面, 总结了铸造铝锂合金的研究现状.结合当前国内外铝锂合金的研究现状对铝锂合金的未来发展做出了展望.      

Electrochemical methods to detect susceptibility of Ni-Cr-Mo-W alloy 22 to intergranular corrosion

Alloy 22 (UNS N06022), a Ni-Cr-Mo-W based alloy, is a candidate material for the outer wall of nuclear waste package (NWP) containers. Even though the alloy is highly stable at low temperatures, it could undergo microstructural changes during processing such as welding and stress relieving. Formation of topologically close-packed (TCP) phases such as μ, P, σ, etc. and Cr-rich carbides could make the material susceptible to localized corrosion. Hence, it is important to correlate the microstructural changes with the corrosion resistance of the alloy by nondestructive and rapid electrochemical tests. In this investigation, different electrochemical test solutions were used to quantify the microstructural changes associated with aging and welding of the wrought alloy 22. The results of double-loop (DL) electrochemical potentiodynamic reactivation (EPR) tests in 1 M H₂SO₄+0.5 M NaCl+0.01 M KSCN solution indicated Cr depletion during initial stages of aging of wrought alloy 22. Results of EPR tests in 2 M HCl+0.01 M KSCN solution at 60 °C correlated well with the Mo depletion that occurred near TCP phases formed during aging of both weld and wrought alloy 22 materials. The EPR test results were compared with standard chemical weight loss measurements specified by ASTM standard G-28 methods A and B.     

非金属夹杂物对不锈钢耐点蚀性能影响的综述

摘要：首先,总结了3种常用的非金属夹杂物对不锈钢耐点蚀性能影响的研究方法,即原位腐蚀观察、微区电化学法、原子力显微镜。其次,总结了硫化物、氧化物、稀土夹杂物3种不同类型夹杂物对不锈钢耐腐蚀性能影响。随着硫化物含量的增多,不锈钢的耐点蚀性能会下降;对于氧化物的影响,目前的研究集中在氧化物的成分对不锈钢耐点蚀性能的影响。不同成分的夹杂物对不锈钢耐点蚀性能的影响机制还不是很清楚;稀土夹杂物对不锈钢点蚀的影响主要与稀土对不锈钢中夹杂物改性有关。而后,汇总了目前提出的夹杂物对不锈钢耐点蚀性能影响的机制,即贫Cr区机制、微缝隙机制、活性机制。贫Cr区机制主要用于解释硫化物引起的点蚀,后2种主要用于解释氧化物引起的点蚀。最后,提出了夹杂物控制提升不锈钢耐点蚀性能的展望。     

The effect of solidification microstructure on the corrosion behavior of a columnar aluminum-copper alloy

The morphological and kinetic nature of corrosion of directionally solidified aluminum-4.5 wt pct copper alloy in the as-cast, solutionized and solutionized-and-aged conditions in air-saturated aqueous 3.5 wt pct NaCl solution were evaluated. In the solutionized and solutionized-and-aged conditions the intergranular attack and pitting are similar to those occurring in solutionized wrought alloys; the extent of attack at long times increases with increasing severity of solidification rate. The as-cast alloy exhibits a cored dendritic structure with significant formation of interdendritic nonequilibrium eutectic. Extensive inter dendritic corrosion of the α-phase containing more than 3.2 wt pct copper is seen; α containing less than 3.2 wt pct copper and the θ-Al₂Cu phase are cathodic. Corrosion of the as-cast alloy is parabolic with time and increases with increasing severity of solidification rate in proportion to the amount of nonequilibrium second phase.     

Effect of thermal and thermo-mechanical processing on the properties of Al-Mg alloys

Results are presented of the influence of thermal and thermo-mechanical processing on the tensile strength and stress corrosion resistance of Al-Mg alloys characterized by different combinations of the ancillary elements Cr, Mn and Zr. As a result of the processes described, the final wrought products exhibit higher yield strengths for a given stress corrosion resistance than conventional materials. This is attributed to the favorable distribution of dislocations and precipitates that is induced by the treatment. The combination of ancil lary elements is an important factor for optimizing the metallurgical properties of the alloys; evidence is given for the role played by the dispersoids containing Cr, Mn and Zr on both the grain structure and the distribution of β(Mp₂Al₃) particles.     

筏板基础大体积混凝土施工防裂措施

通过炼钢转炉基础筏板大体积混凝土施工,介绍了大型设备的基础大体积混凝土的施工技术,分析了大体积混凝土产生裂缝的主要原因,提出了防止混凝土温度裂缝的主要技术措施和控制方法.     

Iron–manganese: new class of metallic degradable biomaterials prepared by powder metallurgy

Abstract

An Fe–35 wt-%Mn alloy, aimed to be used as a metallic degradable biomaterial for stent applications, was prepared via a powder metallurgy route. The effects of processing conditions on the microstructure, mechanical properties, magnetic susceptibility and corrosion behaviour were investigated and the results were compared to those of the SS316L alloy, a gold standard for stent applications. The Fe35Mn alloy was found to be essentially austenitic with fine MnO particles aligned along the rolling direction. The alloy is ductile with a strength approaching that of wrought SS316L. It exhibits antiferromagnetic behaviour and its magnetic susceptibility is not altered by plastic deformation, providing an excellent MRI compatibility. Its corrosion rate was evaluated in a modified Hank's solution, and found superior to that of pure iron (slow in vivo degradation rate). In conclusion, the mechanical, magnetic and corrosion characteristics of the Fe35Mn alloy are considered suitable for further development of a new class of degradable metallic biomaterials.     

Influence of nonequilibrium second-phase particles formed during solidification upon the mechanical behavior of an aluminum alloy

The mechanical behavior of a wrought high strength aluminum alloy is examined as a function of the concentration of second-phase microconstituents. These second-phase particles are located in grain boundaries and interdendritic sites. Their concentration was varied by thermal-mechanical processing. In the areas of strengths, ductility, crack toughness, fatigue, and stress corrosion cracking, empirical results are presented and discussed. Observations are made on changes in the anisotropic character of this category of material with lower concentrations of second phases. Formerly Research Advisor, Frankford Arsenal. This paper is based on an invited talk presented at a symposium on Homogenization of Alloys, sponsored by the IMD Heat Treatment Committee, and held on May 11,1970, at the spring meeting of The Metallurgical Society of AIME, in Las Vegas, Nev.     

The effects of molybdenum and aluminum on the hot corrosion (sulfidation) behavior of experimental nickel-base superalloys

The hot corrosion behavior of a series of wrought nickel-base superalloys containing approximately 13 wt pct Cr was studied as a function of molybdenum content from 0 to 8 wt pct Mo in each of four Al + Ti levels (3 pct Al, 41/2 pet Al, 6 pct Al, and 1 pct Al-31/2 pct Ti). Specimens were tested in a burner rig with a 5 ppm sea salt concentration in a 1 pct sulfur diesel fuel burned at a 30:1 air-to-fuel ratio and were cycled between 1600°F (870°C) or 1800°F (980°C) and room temperature every 50 h during a 1000-h test. It was found that molybdenum significantly reduced the amount of hot corrosion attack at 1600°F (870°C) for the three aluminum-containing series of alloys. For the titanium-containing series of alloys tested at 1600°F (870°C) and all alloys exposed at 1800°F (980°C), molybdenum exerted little influence on hot corrosion behavior. Aluminum was found to markedly increase sulfidation rates at both 1600°F (870°C) and 1800°F (980°C) for all molybdenum levels. Titanium appeared to be beneficial to the hot corrosion resistance of these alloys at 1600°F (870°C) and detrimental at 1800°F (980°C). It was further noted that 1600°F (870°C) represented a more severe sulfidation condition than 1800°F (980°C) under these test conditions.     

我国变形镁合金开发的现状与发展

叙述了变形镁合金的的特性和用途,分析了其加工技术现状,并展望了变形镁合金发展的前景。     

The Fracture Toughness and Toughening Mechanism of Commercially Available Unalloyed Molybdenum and Oxide Dispersion Strengthened Molybdenum with an Equiaxed,Large Grain Structure

Commercially available molybdenum and oxide dispersion strengthened (ODS) molybdenum produced by powder metallurgy (PM) methods were subjected to tensile testing, fracture toughness testing, and examination of the toughening mechanism. Both PM and ODS molybdenum have an equiaxed grain size that is larger in scale than comparable wrought products. This results in lower tensile strength and a higher tensile ductile-to-brittle transition temperature (DBTT) for PM and ODS molybdenum compared to wrought product forms. Although the grain size for PM molybdenum is large and the oxygen content is relatively high, both attributes tending to embrittle molybdenum, the transition temperature and fracture toughness values are comparable to those observed for wrought molybdenum. Crack initiation at grain boundaries and the center of grains where pores are present were observed to leave ligaments for the PM molybdenum that are similar in scale to those observed for wrought molybdenum. This is a similar toughening mechanism to the ductile laminate mechanism observed for wrought molybdenum. The larger oxide particle size for PM ODS molybdenum produces larger cracks that result in lower fracture toughness values and a higher DBTT in comparison to PM molybdenum. The impact of the grain size, grain shape, and oxide particles on the toughening mechanism and resulting properties is discussed.     

The oxidation resistance of fine-grained sputter-deposited 304 stainless steel

The air oxidation of free standing 0.1 cm thick sputter-deposited and wrought 304 stainless steel specimens was studied and the long term oxidation weight gains of the sputterdeposited material were much less than weight gains for the wrought material at 800, 900, and 1000°C. The amount of scaling was also much less on the sputtered material and a thin, adherent oxide formed. The oxide on the sputtered material was more uniform in composition and was higher in chromium and manganese compared to oxide on wrought stainless and eventually formed MnCr₂O₄ after long periods of exposure. No stratified oxide layers, as typically observed in wrought stainless steel, formed on the fine-grained sputtered material. The improved scaling resistance of the sputter-deposited steel was attributed to a combination of grain boundary enhancement of chromium diffusion, reduced stresses in the oxide and mechanical keying of the oxide to closely spaced grain boundaries. The stability of grain size for the sputtered material (grain size ≤ 6 μm) also contributed to the better oxide adherence.     

Substratum topography influences susceptibility of Salmonella enteritidis biofilms to trisodium phosphate

Established (48- and 72-h) Salmonella enteritidis biofilms grown in glass flow cells with or without artificial crevices (0.5-, 0.3-, and 0.15-mm widths) were subjected to a 10% trisodium phosphate (TSP) solution under different flow regimens (0.3, 0.6, 1.2, and 1.8 cm s-1). The abundance of biofilm remaining after TSP treatment, the biocidal efficacy of TSP, and the factors which contributed to bacterial survival were then evaluated by using confocal laser microscopy and a fluorescent viability probe. Biofilm age affected the amount of biofilm which remained following a 15-s exposure to TSP. After TSP treatment of 48-h biofilms, 29% of the original biofilm remained at the biofilm-liquid interface, whereas 75% of the biofilm remained at the base (the attachment surface). Following TSP treatment of 72-h biofilms, 27% of the biofilm material remained at the biofilm-liquid interface, 73% remained at the 5-micron depth, and 91% remained at the biofilm base. Results obtained using the BacLight viability probe indicated that TSP exposure killed all the cells in 48-h biofilms, whereas in the thicker 72-h biofilms, surviving bacteria (approximately 2% of the total) were found near the 5- and 0-micron depths. In the presence of artificially constructed crevices, an inverse relationship was shown to exist between bacterial survival (ranging from approximately 13 to 83% of total biofilm material) and crevice width. This relationship was further influenced by the velocity of TSP flow; high TSP flow velocities (1.8 cm s-1) resulted in the lowest number of surviving bacteria at the base of crevices (approximately 42% survival). Extended time courses demonstrated that after TSP stress was relieved, biofilms continued to grow within crevices but not in systems without crevices. It is suggested that advective TSP flux into crevices and through the biofilm matrix was enhanced under conditions of high flow. These results suggest that the inherent roughness of the substratum on which the biofilm was grown and the timing of TSP application are important factors controlling the efficacy of TSP treatment.     

The effect of protective coatings on the high temperature properties of a gamma prime-strengthened Ni-base superalloy

The present study examined the influence of chrome-aluminide coatings on the creep and stress rupture properties of a wrought Udimet-520 nickel-base superalloy used in gas turbine blade applications. Creep and stress rupture tests were conducted at 802 °C (1475 °F) on coated and uncoated wrought bars in the fully heat treated condition. The tests showed that the application of the chrome-aluminide coatings caused a marked deterioration in rupture strength and ductility. Masking procedures used to protect the turbine blade roots during coating of the Ni-base superalloy also affected the rupture strength or rupture ductility. The mechanical behavior in the coated creep resistant alloy was correlated with the microstructure and is discussed in terms of possible controlling processes.     

钛及钛合金在汽车工业中的应用

介绍了汽车中使用钛及钛合金各类加工材的可能性。通过分析和使用事例来指导我国汽车工业中使用钛及钛合金加工材。     

Si、Na等杂质元素对W－Ni－Fe高比重合金性能和组织的影响

在钨粉中掺入硅和钠元素，在Ｗ－Ｎｉ－Ｆｅ合金混合料中添加纯硅粉，通过实验得出硅和钠对高比重钨合金的力学性能会产生不利的影响。硅和钠形成了氯化物夹杂，在夹杂物周围存在孔隙。文中分析了夹杂物周围孔隙形成的机制，还根据夹杂物的成分，分析了Ａｌ、Ｍｇ、Ｃａ、Ｍｎ、Ｔｉ等金属元素对合金的影响。