Remember the future that was coming soon? Plastic engines would laugh at weight. Handbag-sized ceramic turbines would equal the power of 7-liter V-8s while sipping fuel. Nuclear power, too cheap to meter. Giant space cruisers, leaving for Alpha Centauri. It’s grand to discover that chunks of the long-ago optimism remain real. In the 1960s, Lockheed developed a material called “Lockalloy,” which had a vastly greater ratio of stiffness to weight than the best steels or aluminums. Used in such systems as the YF-12 Blackbird and the Minuteman ICBM, it was what is now called an MMC, a Metal Matrix Composite made of 38 percent aluminum alloy and 62 percent beryllium, which is super light and super stiff. This was not an alloy in the sense that so many metals are—a solid solution of small percentages of one or more alloying elements in a whole made up mostly of, say, aluminum or iron. Lockalloy was made by generating tiny particles consisting of crystalline dendrites of beryllium, coherently coated in an aluminum alloy, then compacting the particles into solid form by multi-step special processing. Why go to this trouble? Why not just make parts out of beryllium itself? The problem: Beryllium doesn’t form a solid willingly; it remains like very tightly packed sand, refusing to form a dense solid. But with the aid of an aluminum matrix, this drawback was removed. By the late 1970s, this super trick future material had gone out of production. The 1950s and ’60s had been an explosive era of rapid technology development in the US, particularly in aerospace and electronics, but later the watchword changed from innovation at any price to implementation at a profit. Never mind the trick stuff, show me something we can sell this week. In 1990, Materion Beryllium & Composites reintroduced the aluminum-beryllium MMC as AlBeMet, and the specialist engine firm Ilmor had pistons and other highly stressed engine parts made from it in their work for Mercedes. Turns out, the material has not only high rigidity-to-weight but also conducts heat extremely well and has high fatigue resistance. The governing body of Formula 1, the FIA, banned the material in 1998, and followed that up by a more general ban against materials having greater than a specified level of stiffness-to-weight. The promise of such light parts was that half-weight pistons and rods would work with much smaller crankshaft counterweights, in turn allowing smaller crankcases. You can imagine the cascade effect. In a word: revolution. But the racing business finds it necessary to gradually turn the motorsports it controls into thinly disguised vintage events. There are lists of banned materials and techniques, deemed to be “destabilizing.” We can’t have two teams up front, racing with AlBeMet pistons, while the rest of the field toils along 10 seconds back with pistons made of 76-year-old RR58 aluminum, or 60-year-old 2618. Who knows? Maybe, as in the actual vintage classes, there will soon be rules banning any material or innovation developed after a certain cut-off date. Gotta stop technology creep! There are stiff, strong, and light materials other than beryllium that can be made part of an aluminum MMC. One of them is silicon carbide, the high hardness ceramic commonly used as an abrasive. As with Lockalloy/AlBeMet, the processing required is neither simple nor cheap. One such material is AMC-225xe, which is 75 percent 2124 aluminum-copper alloy plus 25 percent ultrafine (3 micron) silicon carbide particles. A room temperature tensile strength more than twice that of the leading piston alloy 2618 is claimed, with a ten million cycle rotating beam fatigue test survival stress over twice that for 2618. Folks have made pistons, cylinder liners, con-rods, rockers, valve spring retainers, and race car suspension uprights of this stuff. You need diamond tooling to machine it, but you already need that to finish the familiar and widely used cylinder hard-plating Nikasil, which just happens to be a familiar metal matrix composite—a matrix of nickel containing 5 percent tiny silicon carbide particles (by volume). Eek! Horrors! Time to ban technology itself! It’s everywhere!Gadget Reviews: mamaktalk.com
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