Work your metal matrix.The automotive industry The automotive industry is the industry involved in the design, development, manufacture, marketing, and sale of motor vehicles. In 2006, more than 69 million motor vehicles, including cars and commercial vehicles were produced worldwide. recognizes that weight reduction and improved engine efficiency will make the greatest contribution to improved fuel economy with current powertrains. This is evidenced by the increased use of aluminum alloys in engine and chassis components. Aluminum and magnesium castings in this sector have grown in leaps and bounds over the past five years to help engineers design and manufacture more fuel efficient cars. The low density and high specific mechanical properties of aluminum metal matrix composites Metal matrix composite A material in which a continuous metallic phase (the matrix) is combined with another phase (the reinforcement) that constitutes a few percent to around 50% of the material's total volume. (MMC See MultiMediaCard and Microsoft Management Console. ) make these alloys one of the most interesting material alternatives for the manufacture of lightweight parts for many types of vehicles. With wear resistance and strength equal to cast iron, 67% lower density and three times the thermal conductivity thermal conductivity A measure of the ability of a material to transfer heat. Given two surfaces on either side of the material with a temperature difference between them, the thermal conductivity is the heat energy transferred per unit time and per unit , aluminum MMC alloys are ideal materials for the manufacture of lightweight automotive and other commercial parts. MMC's desirable properties result from the presence of small, high strength ceramic particles, whiskers See metal whiskers. or fibers uniformly distributed throughout the aluminum alloy matrix. Aluminum MMC castings are economically competitive with iron and steel castings Steel casting is a manufacturing process in which molten metal is poured into a mold, allowed to solidify within the mold, and then the mold is broken and the solid piece is taken out. in many cases. However the presence of these wear resistant particles significantly reduces the machinability of the alloys, making machining costs higher due mainly to increased tool wear. As a result, the application of cast MMCs to components requiring a large amount of secondary machining has been somewhat stifled sti·fle 1 v. sti·fled, sti·fling, sti·fles v.tr. 1. To interrupt or cut off (the voice, for example). 2. . Most components do not require the high performance capability of aluminum MMCs throughout their entirety. An un-reinforced cast alloy may accomodate the stresses in these areas. Reinforcement of only the high stress regions of a component is referred to ,is selective reinforcement. This approach to component design and manufacture optimizes the material for the application, reduces the cost of the cast MMC part and lowers machining costs. Be Selective Selective reinforcement has been applied to the production of ring grooves and combustion bowl rim regions of pistons for both gasoline and diesel engines and integral cylinder liners for production gasoline engines gasoline engine: see internal-combustion engine. gasoline engine Most widely used form of internal-combustion engine, found in most automobiles and many other vehicles. . For the ring groove mind cylinder liner applications, the reinforcement predominantly improves wear resistance. Application of short fiber reinforcement to the bowl rim increases its elevated temperature properties. The use of selective reinforcement in a clutch disk and ventilated ven·ti·late tr.v. ven·ti·lat·ed, ven·ti·lat·ing, ven·ti·lates 1. To admit fresh air into (a mine, for example) to replace stale or noxious air. 2. brake disk have been considered but not vet entered production. Short fiber-reinforced composite materials composite material or composite, any material made from at least two discrete substances, such as concrete. Many materials are produced as composites, such as the fiberglass-reinforced plastics used for automobile bodies and boat hulls, but the provide higher performance benefits than the discontinuously reinforced particulate par·tic·u·late adj. Of or occurring in the form of fine particles. n. A particulate substance. particulate composed of separate particles. aluminum composites. Their manufacturing costs are slightly higher, but because it's likely that the value of weight saved in a vehicle will increase drastically over the next few years, selectively reinforced cast aluminum components used for vehicle and engine weight reduction are increasingly probable. The mechanical properties of selectively reinforced MMCs are a function of the fiber properties, the orientation of the fibers and the amount of fibers. Thus, the design engineer needs additional information, such as the mechanical properties of the cast aluminum MMC as a function of fiber quantity, chemistry and orientation. If the fibers are located in a planar A technique developed by Fairchild Instruments that creates transistor sublayers by forcing chemicals under pressure into exposed areas. Planar superseded the mesa process and was a major step toward creating the chip. , random orientation, the mechanical properties expectedly will be the same in all planar directions. Fiber Content Recent research results serve as a first step toward the design and production of selectively reinforced aluminum MMC components. In the study, vertical squeeze cast equipment was used to pressure infiltrate infiltrate /in·fil·trate/ (in-fil´trat) 1. to penetrate the interstices of a tissue or substance. 2. the material or solution so deposited. in·fil·trate v. 1. liquid AlSiCuMg alloy, a modified AA319.0, into rectangular preforms containing different volume fractions of alumina alumina (əl  `mĭnə) or aluminum oxide, Al2O3, chemical compound with m.p. about 2,000°C; and sp. gr. about 4.0. (NF and SF) and
alumina-silica (CF) short ceramic fibers. The preforms were preheated in
air to 1,360F (755C) and placed into a heated four-cavity steel die,
which was sprayed with a die coating before each run.After thermal treatment Thermal treatment is a term given to any waste treatment technology that involves high temperatures in the processing of the waste feedstock. This commonly, although not exclusively involves the combustion of waste materials. to either a T5 or T7 condition, four test blanks were sawn from each casting and radiographed to be classified by quality in accordance with ASTM ASTM abbr. American Society for Testing and Materials E155. Test blanks with a quality level of Grade B or better were machined into tensile test specimens. Tensile testing established the quantitative effect of reinforcement chemistry and quantity and thermal treatment on mechanical properties. As expected, the resultant tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its is a function of the amount of fiber added and the mechanical properties of the ceramic fibers. The tensile strength of the CF and SF fibers are of the same order of magnitude A change in quantity or volume as measured by the decimal point. For example, from tens to hundreds is one order of magnitude. Tens to thousands is two orders of magnitude; tens to millions is three orders of magnitude, etc. , and resultant tensile strength of the fiber-reinforced matrix (FRM FRM From FRM Form FRM Fixed-Rate Mortgage FRM Financial Risk Manager (GARP) FRM Fondation pour la Recherche Médicale FRM Financial Resource Management FRM Final Rulemaking FRM Fiber-Reinforced Metal FRM Federal Reference Methods ) made with these fibers also is of the same order of magnitude. The higher tensile strength of the NF fibers is reflected by higher tensile strength in the aluminum FRM. The elastic modulus elastic modulus or elastic constant In materials science and physical metallurgy, any of various numbers that quantify the response of a material to elastic or springy deflection. of the FRM demonstrated a similar response. The T7 heat treatment increased both the yield and ultimate tensile strengths. Not expected were the higher elastic modulus values exhibited by the T7 heat-treated samples. Image analysis confirmed that fiber orientation was not the reason for the difference. Scanning electron microscopy electron microscopy Technique that allows examination of samples too small to be seen with a light microscope. Electron beams have much smaller wavelengths than visible light and hence higher resolving power. and x-ray diffraction analysis of T7 heat treated samples confirmed the presence of an aluminum-magnesium oxide (spinel spinel, magnesium aluminum oxide, MgAl2O4, a mineral crystallizing in the isometric system, usually as octahedrons. It occurs as an accessory mineral in basic igneous rocks, in aluminum-rich metamorphic rocks, and in contact-metamorphosed ) at the interface between the fibers and the aluminum matrix. The chemical reaction at the interface could have been the cause of the increased strength of the fiber-matrix interface and provided enhanced load transfer from the matrix to the fibers. The result was the increased elastic modulus observed for the T7 heat-treated materials. Optical metallography metallography Study of the structure of metals and alloys, particularly using microscopic and X-ray diffraction techniques. Visual and optical microscopic observation of metal surfaces and fractures can reveal valuable information about the crystalline, chemical, and showed that the short fibers have essentially a planar random orientation in the FRM. However, as the volume percent of fiber in the preform pre·form tr.v. pre·formed, pre·form·ing, pre·forms 1. To shape or form beforehand. 2. To determine the shape or form of beforehand. n. 1. increases, there is a slight preferential orientation in the tensile axis of the the diameter of the sphere which is perpendicular to the plane of the circle. See also: Axis specimens. The data also showed that fiber diameter influenced preferred orientation. The larger diameter NF fibers orient differently than the smaller diameter CF and SF fibers. [FIGURES 1-3 OMITTED] Costing MMCs The property testing results clearly indicate that the highest performance is obtained by reinforcing the 319 metal matrix with the NF chopped fibers. However, knowing the cost to obtain this performance is critical for future applications. In this study, the collected mechanical property data and estimated costs to manufacture generic short-fiber preforms were used to calculate the relative values (cost per property) of the three fibers used to make the FRM test castings. These calculated values provide a guideline for selection of fiber type to meet the needs of the application. Because preform size has an impact on the ratio of fiber cost to processing cost, the relative costs to manufacture short-fiber preforms were estimated for small, medium and large preforms. The volume of a small preform is 1.5 cu. in. (25 cu. cm); a medium preform is 4.8 cu. in. (75 cu. cm); and a large preform is 9.2 cu. in. (150 cu. cm). The resultant relative preform costs are listed in Table 5. Fiber Values The relative cost values for the preforms were divided by the relative property values to obtain a relative value for each type of fiber (Table 6). These are relative fiber values (cost per performance) and are not to be used for estimating actual costs to fabricate preforms for specific applications. Preform size has a significant effect on relative fiber value. Small preforms showed little difference in relative fiber value, making it difficult to prove that one fiber has higher value than the others. This parity among fibers suggests that the use of small preforms could be more economically beneficial. The NF chopped fibers provide higher properties at lower volume fractions, but according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. the value calculations, they may not be cost effective in preforms larger than 1.5 cu. in. (25 cu. cm). This article was adapted from AFS A distributed file system for large, widely dispersed Unix and Windows networks from Transarc Corporation, now part of IBM. It is noted for its ease of administration and expandability and stems from Carnegie-Mellon's Andrew File System. AFS - Andrew File System Transactions papers 05-147 and 06-085 presented at the 109th and 110th Metalcasting Congresses. For More Information "Cast Metal Matrix Composites: Past, Present and Future, " P. Rohatgi, 2001 AFS Transactions (01-133). Gerald Gegel is owner and president of Material Process & Consultancy, Morton, III. David Weiss There are several individuals of note named David Weiss, including:
Table 1. Ceramic Preforms Used to Manufacture Fiber-Reinforced
Aluminum Composites and Their Nominal Mechanical Properties
Material Fiber Nominal Tensile Elastic
ID Chemistry Volume Strength Modulus
Fraction, % (M Pa) (GPa)
CF 47AI203-53Si02 15 & 25 1,000 120
NF 99A1203-Si02 9 & 16 3,000 380
SF 94AI203-4Si02 15 & 25 1,500 300
Table 2. Effect of Fabrication Variables on Ultimate Tensile
Strength of Squeeze Cast 319 FRM
CF NF SF
Fiber Volume % T5 T7 T5 T7 T5 T7
0 224.2 251.9 224.2 251.9 224.2 251.9
7 -- -- 244.9 287.8 -- --
15 213.6 254.6 245.9 288.1 202.5 249.2
25 204 244 -- -- 201 248
Table 3. Effect of Fabrication Variables on Yield Strength
of Squeeze Cast 319 FRM
CF NF SF
Fiber Volume % T5 T7 T5 T7 T5 T7
0 155.3 198.1 155.3 198.1 155.3 198.1
7 -- -- 162.7 201.5 -- --
15 164.4 180.2 192.4 217.9 163.4 175.5
25 175.6 205.4 -- -- 187.7 232.2
Table 4. Effect of Fabrication Variables on Elastic Modulus
of Squeeze Cast 319 FRM
CF NF SF
Fiber Volume % T5 T7 T5 T7 T5 T7
0 75.1 75.5 75.1 75.5 75.1 75.5
7 -- -- 83.1 86.9 -- --
15 77 80.1 94.2 97.8 83.3 84.9
25 78.2 83.7 -- -- 87.3 94.7
Table 5. Relative Cost Factors for Manufacture
of Generic 15 Volume % Preforms
CF NF SF
Cleaned Fiber 1.00 4.88 3.75
Small Preform 1.00 1.81 1.48
Medium Preform 1.49 3.87 2.92
Large Preform 2.12 6.97 4.99
Table 6. Relative Fiber Values for Three Preform Sizes
T5-2[degrees]C T7-2[degrees]C
Fiber Property Small Medium Large Small Medium Large
CF Ultimate 1.00 1.49 2.12 1.00 1.49 2.12
Tensile
Strength
0.2% Yield 1.00 1.49 2.12 1.00 1.49 2.12
Strength
Elastic 1.00 1.49 2.12 1.00 1.49 2.12
Modulus
NF Ultimate 1.57 3.36 6.05 1.60 3.42 6.16
Tensile
Strength
0.2% Yield 1.55 3.31 5.96 1.50 3.20 5.76
Strength
Elastic 1.73 3.71 6.67 1.73 3.71 6.67
Modulus
SF Ultimate 1.56 3.08 5.26 1.51 2.98 5.10
Tensile
Strength
0.2% Yield 1.49 2.94 5.02 1.52 3.00 5.12
Strength
Elastic 1.48 2.92 4.99 1.48 2.92 4.99
Modulus
T5-12[degrees]C T7-12[degrees]C
Fiber Property Small Medium Large Small Medium Large
CF Ultimate 1.00 1.49 2.12 1.00 1.49 2.12
Tensile
Strength
0.2% Yield 1.00 1.49 2.12 1.00 1.49 2.12
Strength
Elastic 1.00 1.49 2.12 1.00 1.49 2.12
Modulus
NF Ultimate 1.54 3.29 6.16 1.54 3.29 5.92
Tensile
Strength
0.2% Yield 1.51 3.24 5.76 1.40 3.00 5.39
Strength
Elastic 1.73 3.71 6.67 1.73 3.71 6.67
Modulus
SF Ultimate 1.47 2.90 5.10 1.59 3.13 5.35
Tensile
Strength
0.2% Yield 1.54 3.03 5.12 1.44 2.85 4.87
Strength
Elastic 1.48 2.92 4.99 1.48 2.92 4.99
Modulus
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