Kickoff.NEW YORK New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of -- Components made of a new high-strength aluminum powder metallurgy alloy are expected to replace conventional aluminum components currently used in aging aircraft. Components made with the alloy have the same strength and fracture resistance as the current aluminum parts but exhibit greater stress corrosion resistance, according to Tim Swigart, maechanical engineer at the metals branch, processing and fabrication division, of the Manufacturing Technology Directorate at Wright Patterson Air Force Base Laboratory. The alloy, known as 7093, is a mixture of aliminum, 9 percent zinc, 2.2 percent magnesium, 1.5 percent copper, 0.14 percent zirconium zirconium (zərkō`nēəm), metallic chemical element; symbol Zr; at. no. 40; at. wt. 91.22; m.p. about 1,852°C;; b.p. 4,377°C;; sp. gr. 6.5 at 20°C;; valence +2, +3, or +4. and 0.1 percent nickel, according to Thomas Gurganus, government contracts program manager for Pittsburgh-based Aluminum Co. of America. Alcoa said the 7093 alloy is a "particularly good choice for forgings or extrusions where significant short transverse stresses are encountered and a high degree or resistance to stress corrosion cracking Stress corrosion cracking (SCC) is the unexpected sudden failure of normally ductile metals or tough thermoplastics subjected to a constant tensile stress in a corrosive environment, especially at elevated temperature (in the case of metals). is required." Alcoa developed the alloy under a program sponsored by Wright Laboratory's manufacturing Technology Directorate as a replacement for aluminum 7075-T6. A Wright Laboratory spokesman said that alloy 7093 "exhibits greater stress corrosion resistance than 7075-T6 with no reduction in yeild, strength, ultimate tensile strength and fracture toughness." Swigart said that research started in 1988, when Alcoa and Wright engineers were looking primarily for an alloy with "corrosion resistance and no degradation in mechanical properties" that could replace aluminum alloys already used in aircraft. Engineers found other alloys with greater corrosion resistance but they lacked the required structural strength and fracture toughness. To test 7093's improved structural characteristics, powder metallurgy forgings of the left outboard engine mount for T-38 aircraft were constructed, Wright said. After extensive mechanical property testing, the San Antonio Air Logistics Center at Kelly Air Force Base Kelly Air Force Base was a United States Air Force base located in San Antonio, Texas. In 2001, the runway and land west of the runway became "Kelly Field Annex" and control of it was transferred to the adjacent Lackland Air Force Base. , Texas, approved a modification document to allow the engine mount to be installed on a T-38 aircraft for flight test. Several T-38 aircraft which incorporate the new alloy already have been test-flown at Reese Air Force Base Reese Air Force Base was a base of the United States Air Force located near Lubbock, Texas. The base was closed 30 September 1997 after being selected for closure by the Base Realignment and Closure Commission in 1995. in Texas, Swigart said, and two engine mounts were successfully installed and flight tested on T-38 aircraft at NASA's Johnson Space Center, Houston. Local maintenance teams were responsible for inspecting the mount, and Wright has "not heard of any problems," Swigart added. The new alloy is produced by an "inert gas inert gas or noble gas, any of the elements in Group 18 of the periodic table. In order of increasing atomic number they are: helium, neon, argon, krypton, xenon, and radon. atomization Atomization The process whereby a bulk liquid is transformed into a multiplicity of small drops. This transformation, often called primary atomization, proceeds through the formation of disturbances on the surface of the bulk liquid, followed by their process," Alcoa said, and "exhibits a highly refined mi- constructure compared with materials processed by conventional ingot ingot Mass of metal cast into a size and shape such as a bar, plate, or sheet convenient to store, transport, and work into a semifinished or finished product. The term also refers to a mold in which metal is so cast. metallurgy routes." Alcoa said 7093 is similar to "conventional aluminum alloys in fabrication, machining, forming, finishing and joining." |
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