在低、中碳合金钢的中温区内,除板条状铁素体转变外还存在块状铁素体转变。中温块状铁素体的三维形态呈不规则的或等轴的块状,系由较高密度位错的块状亚结构所组成,它可在晶内或晶界形核,非共格长大。在相变时,γ/α间不具有固定的位向关系、惯析面与长大取向。随着形成温度的降低,在块内可出现不同分布方式的碳化物,它们与基体间各具有一定的位向关系和惯析面。在块内、块间或沿晶界可形成富碳的岛状组织,常温下它是由M或M+A所组成,其中马氏体与母相间有K-S和N-W位向关系。初步认为,中温块状铁素体组织的形成是铁原子短程扩散的γ→α转变与碳原子长程扩散并以富碳岛状组织或碳化物的方式出现的综合结果。
The transformation of the massive ferrite, besides the lath one, was observed in the low or medium carbon ahoy steels under middle temperatures. The massive ferrite consiste of densely dislocated substructural chunks, which are equi-axial or irregular on three dimensional morphology. They nucleate and grow noncoherently either in the interior or along the boundary of grains. No definite orientation,namely neither habit plane nor growth orientation, was found during γ→a transformation. The carbides of different arrangements which exist certain orientations and habit planes may be presented in the chunks with the decreasing growth temperature. Some island constituents rich in carbon which is composed of twinned martensite or martensite with retained austenite at room temperature may be also formed in or at the massive ferrite chunks or along the grain boundaries. The two above-mentioned orientations between the martensite and matrix are the relationship of K-S and N-W. It seems to be considered that the formation of middle temperature massive ferrite may be resulted by the γ→α transformation of a short range diffusion of Fe atoms accompanied with a long range diffusion in the way of island rich in carbon or carbide as well
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| [1] | |
| [2] | |
| [3] | |
| [4] | |
| [5] | |
| [6] | |
| [7] | |
| [8] |
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