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Aluminum
MPP is the world's largest producer of structural aluminum powder metallurgy components and is leading the way in the use of powder metal aluminum for a variety of new and existing applications. Aluminum powder metallurgy has been around since about 1960, but high volume commercially acceptable parts were not produced until MPP's Washington Street Division began manufacturing powder metal aluminum camshaft bearing caps for the GM Northstar dual overhead cam engine in late 1992. Since that time, the division has produced more than 45 million cam caps from powder metal aluminum. Simply stated, aluminum is like no other material on earth. Once converted to its metallic state, aluminum's combination of useful properties is extraordinary. Aluminum is: - Light in weight - about a third as heavy as copper or steel.
- Highly resistant to corrosion
- Strong, and it can be made stronger by alloying and heat treatment
- An excellent conductor of heat and electricity
- Nonmagnetic, a valuable property around sensitive electronics
- Outstanding in cryogenic properties - strong, not brittle, in intense cold
- Good machinability
- Good response to a variety of finishing processes, such as anodizing
- Completely recyclable (and, therefore, energy-efficient)
The combination of aluminum's light weight and moderate strength give it an excellent strength-to-weight ratio. Aluminum offers product forms and alloys that surpass any other material. The design flexibility of aluminum is unparalleled, allowing designers to engineer optimum shape and performance for each specific application. Powder metal aluminum can compete successfully with less costly materials because of the advantages it brings in primary and secondary weight savings, structural performance and design flexibility. The Powder Metallurgy Aluminum Process The processing fundamentals for aluminum powder metallurgy are similar to those employed for other powder metal materials. Material Selection - Several grades of powder metal aluminum alloys are commercially available. Most contain additives of copper, magnesium, and/or silicon, as well as a small percentage of lubricant is present in the powder blend, but is entirely absent in the finished product. Pressing - Parts are pressed in conventional presses, using tools made with conventional tool steels or carbides. Because aluminum is soft, compaction and ejection pressures are far lower than those used for ferrous powders. Powder metal aluminum premixes can be compacted to 90% of theoretical density at only 12 tsi (165 MPa) and to 95% at 25 tsi (350 MPa). These lower pressures, combined with aluminum's ductility, reduce the possibility of tool breakage. Sintering - As with conventional powder metallurgy materials, sintering is perhaps the most important of all the operations involved in the manufacture of powder metal aluminum parts. Generally, sintering temperatures for powder metal aluminum are lower than for other powder metallurgy materials, which saves energy. A Winning Combination When you link the usual advantages of powder metallurgy to the attributes of an exceptional material like aluminum, you have a winning combination. Aluminum powder metallurgy offers a number of additional advantages related to the specific properties of basic aluminum. Light Weight Lighter weight is a distinguishing characteristic of powder metal aluminum. In fact, aluminum enjoys better than a 3 to 1 weight advantage over iron, nickel, and copper. Conductivity Excellent conductivity, both electrical and thermal, is also a hallmark of powder metal aluminum. Aluminum powder metallurgy parts are comparable to their wrought counterparts and can be utilized as heat sinks or electrical conductors. See Figure 2 (next page) for a comparison. Corrosion Resistance Powder metal aluminum alloys have excellent resistance to corrosion. In particular, the Al-Mg-Si alloys exhibit extremely high resistance to general corrosion, when compared to ferrous-based products. Parts may also be chromate conversion coated or anodized for increased resistance to corrosion. Hard type anodize finishes can be applied for water-resistant applications. Appearance The natural appearance of powder metal aluminum parts is suitable for most applications where good appearance is a requirement. In addition, a wide range of decorative finishes is available. Many of the decorative and protective treatments currently employed for wrought and cast aluminum alloys can also be applied to aluminum powder metallurgy parts. These include mechanical finishing and etching to achieve textures, coloring for decorative or functional purposes, electroplating, and painting. Machining Powder metallurgy aluminum parts also offer many of the important advantages of wrought aluminum in machining operations, including high cutting speeds, smooth surface finish and superior tool life. Joining and Bonding Powder metal aluminum lends itself to a variety of joining and bonding techniques. Sintered aluminum parts can be successfully fastened by adhesive bonding, although the use of threaded fasteners is a more conventional method of joining multiple parts. Excellent thread characteristics can be obtained in powder metallurgy aluminum parts above the 90% density level. The ductility of parts in the upper density range is also sufficient for self-tapping fasteners. Mechanical and Performance Properties of Powder Metal Aluminum Powder metal aluminum parts can be produced with a range of property levels. Mechanical properties such as tensile strength can vary from 20 ksi (130 MPa) to 50 ksi (330 MPa) depending upon the composition and density of the alloy, sintering practices and thermal treatments. Further secondary processing such as hot or cold forming can yield properties approaching those of conventional wrought aluminum materials. Powder metallurgy aluminum mechanical properties are very good and typically are a significant factor in the material selection process. Click here to download a copy of our 'Amazing Aluminum' Brochure
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