材料科學(xué)與工程基礎(chǔ)1(參考版)
2025-01-02 21:01本頁面
【正文】 ? the environment in which the material will be used。 ? processing have to be done for shaping the material or fabricating a ponent。 semitransparent） 多晶：高孔隙度 （ opaque ） 13 Environmental and Other Effects ? Temperature ? Corrosion ? Fatigue ? Strain Rate High temperature change the structure of ceramics and cause polymers to melt or char Low temperature cause a metal or polymers to fail in a brittle manner, even though the applied loads are low. Figure Increasing temperature normally reduces the strength of a material. Polymers are suitable only at low temperatures. Some posites, special alloys, and ceramics, have excellent properties at high temperatures TEMPERATURE Figure A section through a jet engine. The forward pression section operates at low to medium temperatures, and titanium parts are often used. The rear bustion（尾部燃燒） section operates at high temperatures and nickelbased superalloys are required. The outside shell experiences low temperatures, and aluminum and posites are satisfactory. (Courtesy of GE Aircraft Engines.) Figure A variety of plex ceramic ponents, including impellers（葉輪） and blades, which allow turbine engines to operate more efficiently at higher temperatures. (Courtesy of Certech, Inc.) Figure Polymers are used in a variety of electronic devices, including these puter dip switches, where moisture resistance and low conductivity are required. (Courtesy of CTS Corporation.) Figure Integrated circuits for puters and other electronic devices rely on the unique electrical behavior of semiconducting materials. (Courtesy of Rogers Corporation.) Figure The Xwing for advanced helicopters relies on a material posed of a carbonfiberreinforced polymer. (Courtesy of Sikorsky Aircraft Division— United Technologies Corporation.) ? oxygen or other gases ? Liquid ? Radiation（輻射） , atomic oxygen, debris （碎石，廢石） ? oxygen or other gases (1)Most metals and polymers react with oxygen or other gases, particularly at elevated temperatures. (2) Metals and ceramics may disintegrate . (3) Nonoxide ceramics and polymers may oxidize. liquid ? acid （酸） alkali （堿） salt（鹽） lead
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