 OCTOBER,
2005 FEATURES Brazing in Space: Enabling the Next Frontier Many NASA exploration and space science missions envisioned for the 2010 to 2020 time period will use very large structures and complex platforms — Fig. 1. Delivery of large assets into space presents tremendous technical and economic challenges. It would require a new launch vehicle with enormous lift and cargo capacity to keep the cost of mass-to-orbit at an affordable level. It would also require the spaceflight community to adopt higher failure margin acceptance and risk tolerance standards. In the current economic and political environment, the loss of a large payload would result in a major setback to the space program. J. Villafuerte *Zeroing in on a Lead-Free Solder Database The rising interest in lead-free solders creates a need for complete property data on the various lead-free solder compositions. Circuit designers need these data to assess the impact of the transition on product life, and production engineers need these data to determine processing parameters. Various types of data are available, but they are widely dispersed throughout the literature. One problem with combining data from many sources is that variations in test procedures lead to undesirable scatter. To improve the sharing of this important information, we developed an online database for solder properties emphasizing new lead-free solders. T. A. Siewert et al. Brazing Magnesium Alloys and Magnesium Matrix Composites Methods, filler metals, and fluxes suitable for brazing of cast and extruded magnesium-based alloys were developed in the 1960s and 1970s. Since that time, the furnace, torch, and dip brazing processes have been successfully employed without considerable changes. New interest in brazing magnesium has been recently aroused due to the expansion of use of magnesium alloys in the 1990s and, especially, due to an appearance of high-strength magnesium matrix composites as lightweight advanced structural materials for automotive and aerospace. Magnesium alloys are considered as possible replacements for aluminum, plastics, and steels, primarily because of their higher ductility, greater toughness, and better castability. Production of magnesium almost tripled last decade, and the world production capacity reached 515,000 tons per year in 2002 (Ref. 1). A. E. Shapiro Advanced Milling Technology Helps Identify Phase Transformations Understanding the microstructural development of alloys during weld solidification is centrally important to controlling fusion zone properties (Refs. 1–4). As technology continues to advance, new engineering alloys with complex compositions must often be designed to provide application-specific properties to maximize performance. Invariably, these alloys are subjected to some form of welding during manufacturing, where weld resolidification may cause chemical redistribution resulting in inhomogeneities in fusion zone properties, particularly when compared to the base metal. With the constant market pressure to make products smaller and cheaper, high-energy-density (HED) welding processes such as laser and electron beam welding become attractive options to increase productivity and minimize distortion, particularly when compared to conventional arc welding processes (Ref. 5). However, the extremely high cooling rates associated with HED welding (102–106 °C/s) (Refs. 3, 6) significantly reduce the scale of the fusion zone microstructure compared to conventional arc welding methods (100–103 °C/s)(Ref. 3). M. J. Perricone
THE AMERICAN WELDER Students Explore Welding In Space K. Campbell Tube Welding: The Foundation for Building Your Own Motorcycle How to Choose a Welding Glove J. Swearingen and J. Carter WELDING RESEARCH SUPPLEMENT *Estimation of Cooling
Rate in the Welding of Plates with Intermediate Impactor separation of welding fumes showed the welding process determined particle size distribution N. T. Jenkins et al. |
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Welding Journal (ISSN 0043-2296) is published monthly by the American Welding Society for $90.00 per year in the United States and possessions, $130 per year in foreign countries: $6.00 per single issue for AWS members and $8.00 per single issue for nonmembers. American Welding Society is located at 550 NW LeJeune Rd., Miami, FL 33126-5671; telephone (305) 443-9353. Periodicals postage paid in Miami, Fla., and additional mailing offices. POSTMASTER: Send address changes to Welding Journal, 550 NW LeJeune Rd., Miami, FL 33126-5671. Readers of Welding Journal may make copies of articles for personal, archival, educational or research purposes, and which are not for sale or resale. Permission is granted to quote from articles, provided customary acknowledgment of authors and sources is made. Starred (*) items excluded from copyright.Copyright © 2005 by
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