畢業(yè)設(shè)計(jì)機(jī)械外文翻譯--材料的可機(jī)加工性-材料科學(xué)-全文預(yù)覽
【正文】 posites can be difficult to machine, depending on the properties of the individual ponents, ., reinforcing or whiskers, as well as the matrix material. 4. Thermally Assisted Machining Metals and alloys that are difficult to machine at room temperature can be machined more easily at elevated temperatures. In thermally assisted machining (hot machining), the source of heat—a torch, induction coil, highenergy beam (such as laser or electron beam), or plasma arc—is forces, (b) increased tool life, (c) use of inexpensive cuttingtool materials, (d) higher materialremoval rates, and (e) reduced tendency for vibration and chatter. It may be difficult to heat and maintain a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of hot machining are in the turning of highstrength metals and alloys, although experiments are in progress to machine ceramics such as silicon nitride. SUMMARY Machinability is usually defined in terms of surface finish, tool life, force and power requirements, and chip control. Machinability of materials depends not onl y on their intrinsic properties and microstructure, but also on proper selection and control of process variables. 附錄 2：外文中文翻譯 材料的可機(jī)加工性 一種材料的可機(jī)加工性通常以四種因素的方式定義： （ 1）、分的表面光潔性和表面完整性。 they require harder tool materials. Dimensional tolerance control may be a problem in machining aluminum, since it has a high thermal coefficient of expansion and a relatively low elastic modulus. Beryllium is similar to cast irons. Because it is more abrasive and toxic, though, it requires machining in a controlled environment. Cast gray irons are generally machinable but are. Free carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating tools with high toughness. Nodular and malleable irons are machinable with hard tool materials. Cobaltbased alloys are abrasive and highly workhardening. They require sharp, abrasionresistant tool materials and low feeds and speeds. Wrought copper can be difficult to machine because of builtup edge formation, although cast copper alloys are easy to machine. Brasses are easy to machine, especially with the addition pf lead (leaded freemachining brass). Bronzes are more difficult to machine than brass. Magnesium is very easy to machine, with good surface finish and prolonged tool life. However care should be exercised because of its high rate of oxidation and the danger of fire (the element is pyrophoric). Molybdenum is ductile and workhardening, so it can produce poor surface finish. Sharp tools are necessary. Nickelbased alloys are workhardening, abrasive, and strong at high temperatures. Their machinability is similar to that of stainless steels. Tantalum is very workhardening, ductile, and soft. It produces a poor surface finish。 （ 3） . Force and power requirements。 （ 2） . Tool life obtained。 the higher the oxygen content, the lower the aspect ratio and the higher the machinability. In selecting various elem
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