Powder Metallurgy616

While PM product forms do not currently play an important role in aluminum or titanium alloys, powder metallurgy is important for some of the superalloys. The majority of PM superalloy parts fall into one of two categories. In the first, spherical superalloy powders are produced, screened to remove oversize particles, blended to provide a uniform distribution, loaded into container, vacuum degassed and sealed, and then hot isostatic pressed (HIP) to provide a near net shape. This process is...

Continuous Fiber Aluminum Metal Matrix Composites

Aluminum MMCs reinforced with continuous fibers provides high strength and stiffness. However, because of their high cost, most applications have been limited to aerospace. Boron aluminum (B Al) was one of the first systems evaluated. Applications include the tubular truss members in the mid-fuselage structure of the Space Shuttle orbiter and cold plates in electronic microchip carrier boards. Boron was developed in the early 1960s and was initially used successfully in an epoxy matrix on the...

Melting and Primary Fabrication613

There are three major types of nickel deposits nickel-copper-iron sulfides, nickel silicates, and nickel laterites and serpentines.5 The sulfide deposits, which are located in Canada, provide most of the Western world's supply. The nickel-copper-iron sulfide ore is crushed and ground and the iron sulfide is separated magnetically. The remaining nickel and copper ores are then separated by flotation. The nickel concentrate is roasted, smelted in a reverberatory furnace and converted to a...

Secondary Processing of Discontinuous MMCs

After full consolidation, many discontinuous reinforced MMCs are subjected to additional deformation processes to improve their mechanical properties and produce part shapes. Secondary deformation processing of discontinuously reinforced MMCs helps to break up reinforcement agglomerates, reduce or eliminate porosity, and improve the reinforcement-to-matrix bond. Extrusion can generate fiber alignment parallel to the extrusion axis, but often at the expense of progressive fiber fragmentation....

Trimming and Machining Operations

Composites are more prone to damage during trimming and machining than conventional metals. Composites contain strong and very abrasive fibers held together by a relatively weak and brittle matrix. During machining, they are prone to delaminations, cracking, fiber pullout, fiber fuzzing (aramid fibers), matrix chipping, and heat damage. It is important to minimize forces and heat generation during machining. During metallic machining, the chips help to remove much of the heat generated during...

Slurry Infiltration and Consolidation

Bonanza Wing Leading Edge Skin

Slurry infiltration and consolidation is the most prevalent process used to make glass and glass-ceramic composites, mainly because the processing temperatures used for glass and glass-ceramics are lower than those used for crystalline ceramics. The melting point of crystalline ceramics is so high, that even fibers with interfacial coatings would be either dissolved or severely degraded. Another problem is the large temperature difference between extremely high processing temperatures and room...

Recommended Reading

Precipitation Hardening Microstructure

1 Metallic Materials Properties Development and Standardization, U.S. Department of Transportation, Federal Aviation Agency, D0T FAA AR-MMPDS-01, January 2004. 2 ASM Handbook Vol. 1 Properties and Selection Irons, Steels, and High-Performance Alloys, ASM International, 1990. 3 ASM Handbook Vol. 4 Heat Treating, ASM International, 1991. 4 ASM Handbook Vol. 6 Welding, Brazing, and Soldering, ASM International, 1993. 5 ASM Handbook Vol. 14 Forming and Forging, ASM International, 1988. 6 ASM...

Investment Casting

Titanium alloys are difficult to cast due to their high reactivity they will react with both the atmosphere and the casting mold. However, investment casting Fig. 4.25. Titanium Investment Casting Source The Boeing Company Fig. 4.25. Titanium Investment Casting Source The Boeing Company procedures are now available, that in combination with HIP after casting, can produce aerospace quality near net shaped parts that can offer cost savings over forgings and built-up structure.21 An example of the...