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JOM SEPTEMBER 2004
VOLUME 56, NO.9
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Beyond Nickel-Based Superalloys
Solidification in Nickel-Based Superalloys
Archaeotechnology: Revisiting Damascus Steels |
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The China Factor: Aluminum Industry Impact
By: Warren H. Hunt, Jr.
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Advisors: David A. Alven, Keystone Powdered Metal Co.; Gerhard E. Fuchs, University of Florida |
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Published monthly by The Minerals, Metals & Materials Society for its members, JOM is a technical journal devoted to exploring the many aspects of materials science and engineering.
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BEYOND Ni-BASED SUPERALLOYS
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Refractory- and Precious Metal-Based Superalloys
[p. 27
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Author(s): David A. Alven
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The 2004 TMS Annual Meeting & Exhibition held in Charlotte, North Carolina, featured a three-day symposium on Beyond Nickel-Based Superalloys. The symposium explored material developments for high-temperature applications above the current temperature limit of nickel-based superalloys. This commentary introduces three articles from the symposium, highlighting some recent developments in nickel-based superalloys.
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Chromium and Chromium-Based Alloys: Problems and Possibilities for High-Temperature Service
[p. 28
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Author(s): Y.F. Gu, H. Harada, and Y. Ro
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This article presents an overview of publications on mechanical properties of chromium and chromium-based alloys, with particular emphasis on ductility at low temperature and strength at high temperature. Analysis of rather scattered data suggests that a chromium or chromium-based alloy can be duc-tilized at ambient temperature and is quite capable of being strengthened to high levels at high temperature. A new composition design and process would open new opportunities for chromium-based alloys as structural materials used at temperatures up to 1,300°C.
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Platinum-Group-Metal-Based Intermetallics as High-Temperature Structrural Materials
[p. 34
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Author(s): Y. Yamabe-Mitarai, Y. Gu, C. Huang, R. V÷lkl, and H. Harada
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Research on platinum-group-metal (PGM)-based intermetallic compounds, which are candidates as high-temperature structural materials, is reviewed in this article. The research reviewed focuses on PGM-based L12 and B2 compounds. Alloys with a face-centered cubic and L12 or B2 phase are also reviewed.
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Pt-Al-Cr-Ni Superalloys: Heat Treatment and Microstructure
[p. 40
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Author(s): S. Vorberg, M. Wenderoth, B. Fischer, U. Glatzel, and R. Völkl
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In this study, the microstructure of precipitation-strengthened platinum-based superalloys after homogenization heat treatment and various cooling regimes was investigated. The study focused on the lattice misfit between the γ matrix and γ´ precipitate phase as well as the precipitate morphologies. Water quenching led to a γ single-phase structure, whereas air cooling resulted in the precipitation of 200 nm sized γ´ cubes with 30% volume fraction. Further investigations found that chromium in Pt-Al-Cr-Ni alloys had a strong γ´ promoting effect.
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SOLIDIFICATION IN Ni-BASED SUPERALLOYS
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The Segregation of Elements in High-Refractory-Content Single-Crystal Nickel-Based Superalloys
[p. 44
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Author(s): E.C. Caldwell, F.J. Fela, and G.E. Fuchs
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Nickel-based superalloys are complex alloys that contain ten to 15 elements that are widely used in industries where high-temperature strength and corrosion resistance are required. Alloy additions commonly include Cr, Co, W, Ta, Al, Ti, Re, Mo, and, in some alloys, Ru. Each of these additions can affect the as-cast microstructure due to differences in elemental segregation. A better understanding of the effects of typical additions to nickel-based superalloys on the segregation of the elements in the alloy can help identify potential improvements in the processing of current alloys and the development of new alloys. Therefore, the effects of several common alloying additions on solidification segregation and defects were evaluated. In general, an increase in the degree of elemental segregation was observed with increases in each of the elements listed except cobalt and molybdenum. Increased levels of cobalt and molybdenum resulted in reductions in the segregation of most of the elements in the alloy.
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Carbon-Containing Single-Crystal Nickel-Based Superalloys: Segregation Behavior and Carbide Formation
[p. 50
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Author(s): K.A. Al-Jarba and G.E. Fuchs
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Carbon is added to large single-crystal nickel-based superalloy components to reduce grain defects. In this study, the effect of carbon additions on the microstructure of a model nickel-based superalloy, LMSX-1, was examined. Previous results have shown that as carbon content increased, the tendency of the alloy to form all types of solidification defects decreased. In addition, as the carbon content increased, the as-cast microstructures exhibited a decrease in the amount of γ-γ′ eutectic structure and an increase in the volume fraction of carbides and porosity. The carbides formed in these alloys were mostly script-type MC carbides which formed continuous, dendritic networks in the interdendritic region. Microprobe analysis of the as-cast structures showed that the partitioning coefficients did not change with carbon additions. Therefore, the reduction in defect formation with increasing carbon content could not be attributed to changes in segregation behavior of alloying elements. Instead, the presence of these carbides in the interdendritic regions of the alloy appeared to have prevented the thermosolutal fluid flow
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A Freckle Criterion for the Solidification of Superalloys with a Tilted Solidification Front
[p. 56
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Author(s): Wan-Hong Yang, John J. deBarbadillo, Koki Morita, T. Suzuki, Wei Chen, and Keh-Minn Chang
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A freckle citerion developed from M.C. Fleming's macrosegregation theory was extended to consider the effect of the slope of the solidification front. Such slopes are always associated with the remelting of alloy ingots and are frequently encountered in the directional solidification of single crystal and directionally solidified blades. When experimental verification of the criterion was carried out using the horizontal directional solidification method, dendrite growth rate was found to be a key factor in the formation of freckles. The criterion derived considering the slope of the solidification front describes the occurrence of freckles relatively well. Critical values for freckle formation were obtaine for a few nickel-base superalloys.
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The China Factor: Aluminum Industry Impact
[p. 21
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Author(s): Warren H. Hunt, Jr.
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The emergence of China as a global economic force has influenced the technical enterprise generally and a number of industries specifically. The aluminum industry is an example, with effects on consumption and demand as well as production and supply. This article reviews these areas from both a historical and future perspective.
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Strategies for Metal Processing Industries: Competing in Today's Global Economy
[p. 25
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Author(s): Diran Apelian
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Annually, the Metals Processing Institute sponsors a symposium on a topical theme relevant to metal processing industries. This year's topic addressed the issues facing manufacturing industries, and specifically outsourcing to China and India, labor issues, knowledge creation and sustained innovation. The title of this year's symposium was Business and Technical Strategies for Metal Processing Industries . . . to Compete in Today's Global Economy. The symposium was co-sponsored by TMS, ASM International, the American Foundry Society, the North American Die Casting Association, and the Metal Powder Industries Federation. This conference review presents highlights of the presentations.
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Kid Geniuses: Fame, Fortune, and Science Fairs
[p. 13
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Author(s): Maureen Byko
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Every year, high-school students are rewarded with substantial sums of money, media attention, and university recruiting usually reserved for athletes by participating in one of several U.S. science competitions. The students who succeed are diverse, so searching for the formula for creating a super-scientist is futile. This feature article introduces the leading science competitions and some of the talented youths who have participated in them.
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The Continuing Study of Damascus Steel: Bars from the Alwar Armory
[p. 17
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Author(s): J.D. Verhoeven, A.H. Pendray, and W.E. Dauksch
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The authors published a paper in this journal in 1998 titled "The Key Role of Impurities in Ancient Damascus Steel Blades." Because of the continued popularity of the on-line version of this paper, additional experiments were conducted on some three-century old Damascus bars. The results of those experiments are reported in this paper.
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In the Final Analysis
[p. 4
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Author(s): James J. Robinson
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The cover image this month is a rendering on anodized titanium plate of a classic Chinese tale. The cover is more than pleasing to the eye; it relates to the content within the issue. This editorial explains the connection between content and cover, and also describes the process by which the art was made.
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Meetings Calendar
[p. 62
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Author(s): Anonymous
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A monthly round-up of soon-to-be-held meetings and upcoming calls for papers.
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Materials Resource Center: Jobs, Consultants, Marketplace
[p. 66
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Author(s): Various
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Positions and services available. (You may view "Consultants Directory" or "Classifieds" in HTML format or click on the button to download both departments as they appear in the print version of the journal.)
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News and Update
[p. 7
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Author(s): Anonymous
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A special edition featuring selected 2003 annual report summaries from the global superalloys industry.
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End Notes: Things Other
[p. 72
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Author(s): Brendan Baker
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Crossing Borders to Engineer a Better Future, Part III: Are You at Peace?
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