高温淬火Co_(72.7)C_(11.8)Si_(15.5)磁性合金的结构和相转变

Structure and phase transformation for Co_(72.7)C_(11.8)Si_(15.5) magnetic alloy quenched at high temperature

用X射线衍射、透射电子显微镜、场致发射扫描电镜和电子探针研究了Co72 .7C11.8Si15.5合金在 10 0 0℃均匀化退火 7d后 ,水淬至室温的相变和相结构。结果表明 :合金由两个相组成 ,一个是具有密排六方 (hcp)结构的基体Co固溶体 ,其晶格常数a =0 .2 5 0 5nm ,c=0 .40 73nm ;另一个是具有六方 (hex)结构的第二相石墨 ,其晶格常数a =0 .2 46 5nm ,c =0 .6 711nm。X射线衍射没有探测到高温fcc Co相的 (2 0 0 )衍射峰 ,表明fcc Co相已完全转变为hcp Co相 ,平衡转变温度在 10 0 0℃以上。在Co金属中复合添加C和Si元素可以容易地获得室温稳定的hcp结构。

The structure and phase transformation were investigated for Co 72.7 C 11.8 Si 15.5 alloy homogenized at 1 000 ℃ for 7 d, then quenched in water by means of X ray diffraction, TEM, FESEM and EP. The alloy consists of both hcp Co as matrix ( a = 0.250 5 nm, c =0.407 3 nm) and hexagonal graphite as the second phase( a =0.246 5 nm, c =0.671 1 nm). No (200) reflection of fcc Co high temperature phase is detected, which shows that the phase transformation from fcc to hcp has been completed, and the transformation temperature in equilibrium is over 1 000 ℃. Stable hcp Co alloy is readily obtained by adding C and Si elements into Co metals. [