第六章 金属材料

Chapter 6 Metallic Materials

1.名词解释：Explain the concepts:

1）黑色金属: 指铁、铬、锰金属及其合金，以铁及铁合金为主。Blank metals: refers to Fe, Cr, Mn and their alloys, mainly are Fe and its alloy.

2）有色金属：除铁、铬、锰以外的金属成为有色金属。Non-ferrous metals: refers to metals except iron, chromium, manganese and their alloys.

3）奥氏体：碳溶解在γ－Fe中的间隙固溶体，它仍保持γ－Fe的面心立方晶格，晶界比较直，呈规则多边形。Austenite: interstitial solid solution formed by carbon dissolves in γ-Fe, it remains face-centered cubic lattice of γ-Fe, the grain boundary is relatively straight, and is regular polygon.

4）马氏体：碳在α－Fe中的过饱和固溶体，晶体结构为体心四方结构，中高碳钢中加速冷却通常能够得到这种组织。Martensite: supersaturated solid solution formed by the carbon dissolves in α-Fe, the crystal structure is body-centered tetragonal structure, it can be obtained by accelerated cooling the high-carbon steel.

5）超耐热合金：在700～1200℃高温下能长时间保持所需力学性能，具抗氧化、抗腐蚀能力，且能满意工作的金属材料。Super heat-resistant alloys: materials that can maintain the required mechanical properties at high temperature of 700 to 1200 ℃ for a long time. They are antioxidant, corrosion resistant and can work satisfactory.

6）金属固溶体：指一种溶质元素（金属或非金属）原子溶解到另一种溶剂金属元素（较大量的）的晶体中形成的一种均匀的固态溶液。Metal solid solutions: refers to a homogeneous solid solution that formed by a solute elements (metal or nonmetal) atoms dissolve into a solvent metal element (relatively large).

7）金属间化合物：指金属和金属之间，类金属和金属原子之间以共价键形式结合生成的化合物，具有不同于其组成元素的长程有序晶体结构和金属基本特性。Intermetallic compounds: refers to compounds that formed between the metal and the metal atoms by covalent binding. They have basic characteristics of metal and long-range ordered crystal structure.

2.简述形状记忆合金原理。Describe the principle of shape memory alloys.

答：形状记忆合金是指具有一定初始形状的材料经形变并固定成另一形状后，通过热、光、电等物理刺激或化学刺激的处理又可恢复成初始形状的合金。其形状记忆效应源于某些特殊

结构合金在特定温度下发生的马氏体相－奥氏体相组织结构相互转换。热金属降温过程中，面心立方结构的奥氏体相逐渐转变成体心立方或体心四方结构的马氏体相，这种马氏体一旦形成，就会随着温度下降而继续生长，如果温度上升它又会减少，以完全相反的过程消失。Answer:Shape memory alloy refers to material that has a certain initial shape, can change to another shape, and can restore the initial shape by heat, light, electricity and other physical stimulation or chemical stimulation treatment. The mechanism of shape memory alloy result from the conversion of martensitic and austenitic phase at a particular temperature. In the process of cooling of hot metal, the face-centered cubic structure of austenite phase gradually transformed into the body-centered cubic or body-centered tetragonal martensite phase, once the martensite formation, it will continue to grow with decreasing temperature, if temperature rise, the quantity of martensite phase will reduce and disappear completely in an opposite process.

3.介绍储氢合金类别，并说明其储氢、释氢化学过程。Introduction the category of

hydrogen storage alloy, and explain the chemical process of hydrogen storage alloy when it store and release hydrogen.

答：储氢合金主要有钛系储氢合金、锆系储氢合金、铁系储氢合金及稀土系储氢合金。相对来说，稀土系储氢合金是最好的。储氢合金储氢的化学过程为：H2分子与合金接触时，先吸附在合金表面，H2的H-H键解离，成为原子H，原子H从合金表面向内部扩散，侵入比H原子半径大得多的金属原子与金属的间隙中形成固溶体。固溶于金属中的氢再向内部扩散，这种扩散必须有由化学吸附向溶解转换的活化能。固溶体一被氢饱和，过剩氢原子与固溶体反应生成氢化物。这时，产生溶解热。释放氢时，氢化物吸收热量，并发生分解，将吸收的氢释放出来。

Answer: There are four kinds of hydrogen storage alloy, they are titanium based hydrogen storage alloy, zirconium based hydrogen storage alloy, iron based hydrogen storage alloy and rare earth based hydrogen storage alloy. Relatively, rare earth based hydrogen storage alloy is the best. The chemical process of hydrogen storage alloy is: the H2 molecule adsorbs on the alloy surface of H2, then H-H bond dissociate and become H atom, atomic H diffuse from the alloy surface to the internal space, and invade in the gap of metal atoms and form a solid solution. Hydrogen dissolves in the internal of the metal again, this diffusion is drived by activation energ. The excess hydrogen atoms to generate hydride solid solution and generate heat. When release hydrogen, the hydride absorb heat, and the hydride is decomposed, the H atoms was released.