1. 晶粒（crystalline grain）、晶界（grain boundary）
組成金(jin)屬材料(liao)的(de)小晶(jing)(jing)體，稱為(wei)晶(jing)(jing)粒。晶(jing)(jing)粒與晶(jing)(jing)粒之間的(de)分界面，稱為(wei)晶(jing)(jing)界。
2. 相（phase）、相界(jie)（phase boundary）
在金(jin)(jin)屬或合金(jin)(jin)中，凡成分相(xiang)(xiang)同、結構(gou)相(xiang)(xiang)同并有界(jie)面(mian)互相(xiang)(xiang)隔開的(de)均勻組成部分，稱(cheng)為相(xiang)(xiang)，相(xiang)(xiang)與相(xiang)(xiang)之間(jian)的(de)界(jie)面(mian)，稱(cheng)為相(xiang)(xiang)界(jie)。
3. 固(gu)溶體(ti)（solid solution）
組(zu)成(cheng)(cheng)合金(jin)的(de)一種金(jin)屬元素的(de)晶體中溶(rong)有另一種元素的(de)原子形(xing)成(cheng)(cheng)的(de)固(gu)態相，稱為固(gu)溶(rong)體。固(gu)溶(rong)體一般有較高的(de)強度(du)、良(liang)好的(de)塑性、耐蝕(shi)性以及高的(de)電(dian)阻和磁性。
按溶質原(yuan)子在晶格中的位置(zhi)不同可分為(wei)置(zhi)換固(gu)溶體和間隙固(gu)溶體。
①. 置(zhi)(zhi)換固(gu)(gu)溶(rong)(rong)(rong)(rong)體(ti)：溶(rong)(rong)(rong)(rong)質原(yuan)子(zi)(zi)占(zhan)據溶(rong)(rong)(rong)(rong)劑晶格中的(de)結點位置(zhi)(zhi)而形(xing)(xing)(xing)成的(de)固(gu)(gu)溶(rong)(rong)(rong)(rong)體(ti)稱(cheng)置(zhi)(zhi)換固(gu)(gu)溶(rong)(rong)(rong)(rong)體(ti)。當(dang)溶(rong)(rong)(rong)(rong)劑和溶(rong)(rong)(rong)(rong)質原(yuan)子(zi)(zi)直徑相差不大(da)，一般在(zai)15％以內時，易于形(xing)(xing)(xing)成置(zhi)(zhi)換固(gu)(gu)溶(rong)(rong)(rong)(rong)體(ti)。銅鎳(nie)二元合金即(ji)形(xing)(xing)(xing)成置(zhi)(zhi)換固(gu)(gu)溶(rong)(rong)(rong)(rong)體(ti)，鎳(nie)原(yuan)子(zi)(zi)可在(zai)銅晶格的(de)任意位置(zhi)(zhi)替代銅原(yuan)子(zi)(zi)。
②. 間(jian)(jian)(jian)隙固(gu)溶(rong)(rong)(rong)體(ti)：溶(rong)(rong)(rong)質原(yuan)子分布于溶(rong)(rong)(rong)劑晶格間(jian)(jian)(jian)隙而形成(cheng)的(de)(de)固(gu)溶(rong)(rong)(rong)體(ti)稱間(jian)(jian)(jian)隙固(gu)溶(rong)(rong)(rong)體(ti)。間(jian)(jian)(jian)隙固(gu)溶(rong)(rong)(rong)體(ti)的(de)(de)溶(rong)(rong)(rong)劑是直(zhi)徑(jing)(jing)較大的(de)(de)過渡族金屬(shu)，而溶(rong)(rong)(rong)質是直(zhi)徑(jing)(jing)很小(xiao)的(de)(de)碳、氫等(deng)非(fei)金屬(shu)元素。其(qi)形成(cheng)條件是溶(rong)(rong)(rong)質原(yuan)子與溶(rong)(rong)(rong)劑原(yuan)子直(zhi)徑(jing)(jing)之比必須(xu)小(xiao)于0.59。如鐵碳合金中(zhong)，鐵和碳所形成(cheng)的(de)(de)固(gu)溶(rong)(rong)(rong)體(ti)-鐵素體(ti)和奧氏體(ti)，皆(jie)為間(jian)(jian)(jian)隙固(gu)溶(rong)(rong)(rong)體(ti)。
按固(gu)溶(rong)度(du)來分(fen)類，可分(fen)為有限(xian)固(gu)溶(rong)體和無(wu)(wu)限(xian)固(gu)溶(rong)體。無(wu)(wu)限(xian)固(gu)溶(rong)體只可能是置換固(gu)溶(rong)體。
按溶(rong)質原(yuan)子與溶(rong)劑原(yuan)子的(de)相對(dui)分(fen)布來分(fen)，可分(fen)為無序(xu)固溶(rong)體(ti)和有序(xu)固溶(rong)體(ti)。
4. 金(jin)屬化(hua)合物（metal compounds）
合金中不(bu)同(tong)(tong)元(yuan)素的原(yuan)子相互(hu)作(zuo)用形成(cheng)的、晶格類型和性能(neng)都完全(quan)不(bu)同(tong)(tong)于(yu)其組(zu)成(cheng)元(yuan)素的，具(ju)有(you)金屬(shu)特(te)性的固態相，稱為金屬(shu)化合物。金屬(shu)化合物多數具(ju)有(you)熔點高、硬而(er)脆(cui)的特(te)點，是合金中很重要的強(qiang)化相。
