Fe－1．83C马氏体调幅分解的TEM研究

A TEM STUDY OF SPINODAL DECOMPOSITION IN Fe-1 .83C MARTENSITE

利用透射电镜研究了Ｆｅ－１．８３Ｃ（％）马氏体在室温时效后衍时斑点的漫散射及显微组织变化。利用双倾试样技术得出了漫散时斑强度在倒易空间的分布。结果表明：马氏体斑点呈漫散的角状，其立体形态由对顶的两个四棱锥构成对漫散射的Ｆｏｕｒｉｅｒ分析及ＴＥＭ显微组织分析表明：马氏体在时效时发生了调幅分解，其调幅结构由波长为≈１ｎｍ的主波和波长大于１ｎｍ的次波叠加而成；同时发现Ｆｅ－Ｃ马氏体调幅分解的一个显著特点是，调幅结构时效数月后也未长大。对马氏体正方度的研究表明：在调幅分解过程中碳原子的再分布仅限于Ｏ＿ｚ八面体间隙亚点阵中。

Diffuse scattering and microstructure of Fe-1.83C(%) martensite aged at room temperature was studied by TEM. The intensity distribution of diffuse scattering in reciprocal space was determined by double-tilt technique. The results show that the shape of martensite diffraction spot becomes a diffuse spike after aging, and its 3-dimensional profile appears to be two head-on 4-sided regular pyramids. Fourier analysis of the diffuse scattering suggests that martensite undergoes a spinodal decomposition during aging,the tweed-like modulated structure is composed of a dominant wave with wavelength of about 1 nm and non-dominant waves with longer wavelengths. For the first time it is found that the modulated structure of Fe-C martensite does not grow even after aged for several months.The reason is considered to be due to the strong elastic interactions among carbon-enriched and depleted regions.