9.1高分子材料.PDFVIP

9.1 高分子材料 ·························································································· 256 9.2 陶 瓷 ································································································ 272 9.3 复合材料 ····························································································· 277 本章小结 ···································································································· 281 思考与练习 ································································································· 282 10 工程材料的选用与典型零件的工艺路线分析 ·················································· 283 10.1 选择材料的一般原则和过程 ···································································· 283 10.2 典型零件选材及工艺路线 ······································································· 291 本章小结 ···································································································· 299 思考与练习 ································································································· 299 参考文献 ···································································································· 301 2 纯金属的结构与结晶 本章提要 本章首先介绍金属的晶体结构，提出晶格、晶胞、晶面、晶向等晶体学的一些基本概 念，重点分析典型的3种晶体结构的特征参数，说明晶面指数和晶向指数的确定方法；然 后介绍实际晶体的结构和3种晶体缺陷；最后介绍金属结晶的现象、结晶的热力学条件、 结晶的过程、形核和长大的规律、晶粒大小及其控制方法、铸锭组织，重点阐述金属的结 晶过程和晶粒细化方法。 在外界条件固定的情况下，材料的性能取决于材料内部的构造。这种构造便是组成材料 的原子种类和含量，以及它们的排列方式和空间分布。通常将前者叫作成分，后者叫作组织 结构。金属的结构与其结晶过程密切相关。研究金属的结构和结晶规律，是了解金属材料的 性能、正确选用金属材料、开发新材料的基础。 2.1 纯金属的晶体结构 2.1.1 晶体与非晶体 自然界中的固态物质，虽然外形各异、种类繁多，但都是由原子（离子、分子）堆积而 成的。按其内部原子的堆积情况，可将物质分为晶体和非晶体两大类。 晶体是原子（离子、分子）在三维空间做有规则的周期性排列的物体。非晶体中这些质 点则呈无规则排列，与处于液体的原子排列类似，故非晶体有液态固体之称。 自然界中绝大多数固体都是晶体，如常用的金属材料、半导体材料、磁性薄膜及光学材 料等，而玻璃、松香、沥青等无机材料是非晶体。晶体和非晶体在一定条件下可以相互转化。 例如，金属通常是晶体，但液态金属在激冷的情况下，也可变成非晶体。 由于晶体内部原子排列的规律性，有时某些晶体物质也有规则的外形，如水晶、结晶盐、 天然金刚石等，但实际金属晶体一般看不到规则的外形。 晶体和非晶体还有许多差别。晶体具有固定的熔点，比如铁的熔