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JOM MAY 2005
VOLUME 57, NO.5
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![May 2005 Cover: The Death Star was a looming metallic emblem of all that was evil in the Star Wars universe. The space-based battle station was capable of destroying entire planets with a single, illogical blast of a laser beam. To learn more about the fantastic science of the Star Wars movies, as well as TMS members' ideas on building some Star Wars weapons, see the artilce on page 12. Photo by Lucasfilm Ltd. [Click to enlarge]](http://www.tms.org/pubs/journals/jom/0505/cover-0505.gif)
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.
Prof. John Campbell’s Ten Rules for Making Reliable Castings
[p. 19
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Author(s): Mark Jolly
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John Campbell’s “Casting Rules” were developed over a lifetime of work in the foundry industry and later research at the University of Birmingham. Much of the research work focused on the effect of melt handling at the various transfer stages on the number of defects created and the effect on the reliability of the castings subsequently made. This article provides the author's analysis of Campbell’s ten rules for metal casting.
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Predicting the Occurrence and Effects of Defects in Castings
[p. 29
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Author(s): Malcolm Blair, Raymond Monroe, Christoph Beckermann, Richard Hardin, Kent Carlson, and Charles Monroe
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Casting designs are generally based on strength of materials calculations and the experience of the designer. This process leads to incremental development of designs utilizing factors of safety, which lead to increased component weights and inefficient use of materials. In castings, unquantifiable factors (such as shrinkage, porosity, hot tears, and inclusions) lead to conservative design rules. Nondestructive testing does not give the designer a way to assess the effect of indications on part performance. This article describes recent work to predict the occurrence and nature of defects in castings and determine their effect on performance.
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The Superplastic Forming of Bulk Metallic Glasses
[p. 35
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Author(s): Jan Schroers
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Superplastic forming (SPF) is introduced in this article as a net-shape processing method for bulk metallic glasses (BMGs), commercially known as Liquidmetal® alloys. This method decouples fast cooling and forming of the BMG. Forming takes place in the supercooled liquid region, where the BMG exists as a highly viscous liquid and increases its fluidity with increasing temperature. The SPF method is very similar to techniques used for processing thermoplastics. In this work, a simple flow law is used to quantify the forming ability and to estimate both the potential and the limitations of the SPF method. This process is especially well suited to replicate small features and thin sections with high aspect ratios, which makes this process appropriate for microelectromechanical systems, nano- and microtechnology, jewelry, medical and optical applications, and data storage.
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Stray Grain Formation in the Seed Region of Single-Crystal Turbine Blades
[p. 40
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Author(s): X.L. Yang, P.D. Lee, and N. D’Souza
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Seed crystals are frequently used to provide an off-axial <001> crystallographic orientation to investment cast single-crystal, nickel-based superalloy turbine blades. However, stray grain defects can form during the melt-back of the seed crystal, requiring the use of a helical grain selector between the seed and the blade to remove them. Using meso-scale numerical simulations, the formation mechanisms of these stray grain defects have been investigated. Also investigated was the influence of the seed’s crystallographic orientation relative to blade axis. The model is first validated by comparison to experimental observations and then by its application to a range of casting situations. The results show that initiation of these defects is difficult to avoid. Instead, the impact of stray grains should be controlled during their growth.
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Current Wrought Magnesium Alloys: Strengths and Weaknesses
[p. 46
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Author(s): Collen J. Bettles and Mark A. Gibson
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The opportunities for extruded and sheet magnesium products in the automotive industry, in particular, are increasing as the quest for lightweighting gains momentum. However, the current alloys all have limitations and these are accentuated when higher productivity targets are also imposed. This article attempts to summarize the strengths and weaknesses of the current wrought alloys, with particular emphasis on the extrusion process, and also considers alternative processing routes which may be useful in overcoming some of these shortcomings.
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The Use of Wrought Magnesium in Bicycles
[p. 50
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Author(s): Josh Deetz
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The basic properties of magnesium alloys suggest that they would readily find use in bicycles. Magnesium alloys have low density and a high strength-to-weight ratio, are readily extrudable, and some alloys are highly weldable. A lack of information about wrought magnesium alloys, a lack of suppliers to complete the production process, and a lack of information in how to set up a manufacturing plant to process wrought magnesium alloys have contributed to only limited market penetration by magnesium into bicycle applications. This article examines what has worked and what has not in the use of magnesium alloys in the bicycle business.
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The Corrosion Performance of Magnesium Alloy AM-SC1 in Automotive Engine Block Applications
[p. 54
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Author(s): Guangling Song, David StJohn, Colleen Bettles, and Gordon Dunlop
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The magnesium alloy AM-SC1 has been developed as a creep-resistant automotive engine block material. This paper outlines its corrosion performance under laboratory test conditions, considering corrosion on both the external and internal surfaces. This study found that AM-SC1 has a corrosion performance comparable to AZ91 when subjected to an aggressive salt-spray environment or in galvanic-coupling environments. This article further demonstrates that, with the appropriate selection of a commercially available engine coolant, the internal corrosion of AM-SC1 can be maintained at a tolerable level. In addition, internal corrosion resistance can be signifi cantly improved by the addition of fluorides to the coolant solution. It is concluded that AM-SC1 can be successfully used in an engine environment provided that some simple corrosion-prevention strategies are adopted.
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Macroscopic Damage by the Formation of Shear Bands during the Rolling and Deep Drawing of Magnesium Sheets
[p. 57
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Author(s): Fr.-W. Bach, B.-A. Behrens, M. Rodman, A. Rossberg, and G. Kurz
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Most magnesium parts for automobiles are currently produced by die casting, which allows for complex geometries. However, die casting has two significant disadvantages over wrought alloy sheets: it results in poorer mechanical properties and much rougher surfaces. An alternative production route for these parts is deep-drawn and joined magnesium sheets. This article describes an investigation into the effects of the deep-drawing process on magnesium alloys.
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The Influence of Severe Plastic Deformation on the Mechanical Properties of AA6111
[p. 62
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Author(s): KiHo Rhee, Rimma Lapovok, and Peter F. Thomson
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The alloy AA6111 has been chosen in many countries for automotive outer-body panels, but low ductility remains a major obstacle to competition with steel. Equal channel angular extrusion (ECAE) was used as a tool to produce fine-grained structures with enhanced ductility. Conventional grain sizes in the range of 9 μm to 50 μm were used to investigate the influence of severe plastic deformation (SPD) and heat treatment on mechanical properties of AA6111 sheet at room temperature. It has been found that SPD by ECAE followed by heat treatment leads to an increase in both strength and ductility, in addition to high r-value. The increase in mechanical properties was also signifi cantly influenced by heattreatment temperature at the final stage of sheet processing.
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An Optical Technique to Measure Distortion in Heat-Treated Parts In-Situ
[p. 67
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Author(s): Federico Sciammarella and Phillip Nash
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Improvements in the properties of aluminum alloys have made them more popular for structural applications. Using the different heat treatments that are available, aluminum alloys can have a wide variation in properties for different types of applications. The appropriate heat treatments of these alloys are vital in providing the properties needed for their particular applications. Moreover, understanding the effects of heat treatments that may cause distortion to a part is critical. Most of the work carried out in this field is in the form of pre- and post-treatment analysis of a part. In this study, in-situ measurements of the distortions that a heat-treated part undergoes when subjected to rapid heating to temperatures near melting followed by slow cooling were carried out. A numerical model was built to simulate the experiment and the results are compared. This study will provide much-needed insight into the complex occurrences that aluminum parts undergo during heat treatment.
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The (Mostly Improbable) Materials Science and Engineering of the Star Wars Universe
[p. 12
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Author(s): Maureen Byko
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A long time ago, in a studio far, far away, a new universe was unveiled. It was a place teeming with odd life forms, where space vehicles sped above the landscape and where humans, robots, and everything in between coexisted—sometimes harmoniously. It was also a universe of futuristic beings who could fly faster than the speed of light, and yet worked metals using ancient methods. It was a place where vehicles defied gravity in inexplicable ways, and planet-hopping people were unaffected by changing atmospheres. This feature explores the good and bad science of the Star Wars universe.
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In the Final Analysis
[p. 2
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Author(s): James J. Robinson
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This issue of JOM contains the capstone of an unofficial JOM trilogy on the materials science and engineering of enormously popular science fiction and fantasy film franchises. This editorial provides details of the past articles and the rationale behind the May focus on Star Wars.
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News and Update
[p. 4
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Author(s): Anonymous
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Items of Note from the Field, Profession, and Society
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Foundation News
[p. 71
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Author(s): Anonymous
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Read about the benefits of the TMS Young Leaders program, as told by some Young Leaders themselves.
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Meetings Calendar
[p. 72
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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. 75
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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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End Notes: “Smarts and Fashion Sense: Making Science Appealing to Teenage Girls”
[p. 80
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Author(s): Kelly Roncone
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This article describes Lia, a fictional 14-year-old Hispanic girl who can move with equal ease through a mall and a laboratory. She is the centerpiece of an ambitious project to show that girls can be interested in science and still lead normal, social lives.
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![May 2005 Cover: The Death Star was a looming metallic emblem of all that was evil in the Star Wars universe. The space-based battle station was capable of destroying entire planets with a single, illogical blast of a laser beam. To learn more about the fantastic science of the Star Wars movies, as well as TMS members' ideas on building some Star Wars weapons, see the artilce on page 12. Photo by Lucasfilm Ltd. [Click to enlarge]](http://www.tms.org/pubs/journals/JOM/0505/cover-0505.large.gif)