Sintered aluminum powder

Dispersions of flake aluminum powders having surface oxide up to 14 wt % Al O have been pressed, sintered, and worked to a material known as sintered aluminum powder (SAP). This product exhibits high strength at elevated temperatures. Nickel containing small additions of thoria, known as TD-nickel, is also a high temperature cermet. 

Figure 5.82 The strength of different dispersion-strengthened alloys relative to the pure metal strength as a function of relative temperature. Preparation techniques include sintered aluminum powder (SAP), internal oxidation, and salt decomposition. Reprinted, by permission, from A. Kelly, Composite Materials, p. 62. Copyright 1966 by American Elsevier, Inc.

Fine flakes of A1 immediately form an oxide layer (AI2O3). When this powder is used to make sintered alloys, the oxide is retained as a dispersoid. This oxide prevents grain growth as well as dislocation motion, thus producing a high strength, high creep resistant sintered aluminum powder (SAP) alloy. 

The high-temperature strength of nickel alloys may be enhanced significantly by the addition of about 3 vol% thoria (Th02) as finely dispersed particles this material is known as thoria-dispersed (or TD) nickel. The same effect is produced in the aluminum-aluminum oxide system. A very thin and adherent alumina coating is caused to form on the surface of extremely small (0.1 to 0.2 p.m thick) flakes of aluminum, which are dispersed within an aluminum metal matrix this material is termed sintered aluminum powder (SAP). 

Sintering of powdered metals such as aluminum, beryllium, tungsten, and zinc as well as ceramics under pressure is widely practiced as a shaping process, but that is different from the sintering process described here. 

The reforming reactor was built of copper powder, which could be sintered at temperatures between 500 and 700 °C, being low enough to avoid damage to the catalyst. In the same fabrication stage, the Cu/ZnO catalyst with a particle size between 300 and 500 pm was incorporated into the device. Copper and aluminum powder were used as inert materials for parts such as channels and diffusion layers. 

Schuessler et al. [85] applied sintering of copper and aluminum powder to form micro structured plates for an integrated autothermal methanol reformer (see Section 2.7.2). The powders were compressed before sintering at a pressure of 1000 bar. Sintering of copper is performed at temperatures between 500 and 700 °C, which allows for the bonding of the plates in a second sintering step (see the next section). 

Xie GQ, Ohashi O, Chiba K, Yamaguchi N, Song MH, Fumya K et al (2003) Frequency effect on pulse electric current sintering process of pure aluminum powder. Mater Sci Eng A-Stmct Mater Prop Microstmct Process 359 384—390... 

The used mullite (KMlOl, Kyoritsu Materials Ltd, Japan), aluminum (600F, Minaruko Ltd., Japan) and carbon black fine powders ( 4000B, Mitsubishi Chemical Ltd., Japan) have means of the particles size of 780 nm, 5400 nm and 20 nm, respectively. Carbon powder was dispersed well in ethanol using ultra sonic vibration, before the ball-milling. Mullite and aluminum powders were added to earbon ultra-fine powder dispersed ethanol and the powders were mixed well via a Teflon pot and alumina balls for 24 h. To finish reaction (2), the dried mixed powder was heated at 1400 °C for 5 h in a carbon crucible and Ar atmosphere. After that, the formed alumina/ SiC powder was sintered via hot-press at 1800 C for I h in Ar. The sintered... 

Miscellaneous Methods. Powdered metals such as aluminum, chromium, nickel, and copper, along with various aHoys, can be appHed to parts by electrostatic deposition. The metal strip containing the attached powdered metal must be further processed by cold rolling and sintering to compact and bond the metal powder. 

Porous parts and bearings are made by both the press and sinter techniques, whereas filters are made by loose powder sintering. The metals most commonly used for P/M porous products are bron2e, stainless steel (type 316), nickel-base alloys (Monel, Inconel, nickel), titanium, and aluminum. 

Rotational Molding. Hodow articles and large, complex shapes are made by rotational mol ding, usuady from polyethylene powder of relatively low viscosity (57—59). The resin is in the form of a fine powder. A measured quantity is placed inside an aluminum mold and the mold is heated in an oven and rotated at low speed. The resin sinters and fuses, coating the inside of the mold. The mold is then cooled by water spray and the part solidifies, dupHcating the inside of the mold. 

Ceramic matrix composites are produced by one of several methods. Short fibers and whiskers can be mixed with a ceramic powder before the body is sintered. Long fibers and yams can be impregiated with a slurry of ceramic particles and, after drying, be sintered. Metals (e.g., aluminum, magnesium, and titanium) are frequently used as matrixes for ceramic composites as well. Ceramic metal-matrix composites are fabricated by infiltrating arrays of fibers with molten metal so that a chemical reaction between the fiber and the metal can take place in a thin layer surrounding the fiber. 

---