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首页> 外文期刊>ISIJ international >Microstructure of Martensite/Bainite Dual-phase Grey Cast Iron and Its Strengthening Mechanism
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Microstructure of Martensite/Bainite Dual-phase Grey Cast Iron and Its Strengthening Mechanism

机译：马氏体/贝氏体双相灰口铸铁的组织及其强化机理

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摘要

By a process of combinations of microalloying with Ni, Mo and other elements, cast chilled by metal-mold and special heat-treatment, A martensite/bainite (M/B) dual-phase grey cast iron was fabricated. Quenching into oil after austenization at 900℃ for 2 h, the hardness of the sample was above HRC 48. The microstruc-tures of all samples were characterized by optical metallography or X-ray diffraction. The final microstructure was composed of M/B dual-phase and retained austenite. There were some "white-bright zone" composed of few high-carbon martensite plates and retained austenite, full of Mn and Mo elements, concentrating on the boundaries of eutectic cells. The nucleation site and mechanism of bainite were studied by short oil-quenching for 5 s after austenization at 860℃ for 2h. The result showed bainite first nucleated at interface between flake graphite and austenite, and austenite along the direction of flake graphite sharp corner was also tend to transform into bainite. The second site easy for bainite nucleation was the boundary of austenite, also the boundary of "white-bright zone". Strengthening mechanism of M/B dual-phase to this grey cast iron was studied by using pressing-in method to press round head into the surface of corrosive M/B dual-phase grey cast iron. The initiation and extension of cracks were observed through SEM. The result showed that M/B dual-phase could effectively strengthen graphite-matrix interface and restrain cracks extension, tips of high-carbon martensites in "white-bright zone" were another site prone to initiate cracks under pressure. For lake of phase-phase interfaces, the cracks would extend straightly until to the whole interface of "white-bright zone" and matrix.
机译：通过将镍，钼和其他元素进行微合金化，铸模冷却和特殊热处理的组合工艺，制成了马氏体/贝氏体（M / B）双相灰口铸铁。在900℃下奥氏体化2小时后淬入油中，样品的硬度高于HRC 48。所有样品的显微组织均用光学金相或X射线衍射表征。最终的显微组织由M / B双相和残余奥氏体组成。有一些“白亮区”，由很少的高碳马氏体板和残留的奥氏体组成，充满了Mn和Mo元素，集中在共晶细胞的边界上。在860℃奥氏体化2h后，通过短时间的油淬5s研究了贝氏体的形核部位和机理。结果表明，贝氏体首先在片状石墨与奥氏体之间的界面形核，而沿片状石墨尖角方向的奥氏体也倾向于转变为贝氏体。贝氏体容易成核的第二个位置是奥氏体的边界，也是“白亮区”的边界。通过压入法将圆头压入腐蚀性的M / B双相灰口铸铁表面，研究了M / B双相对灰铸铁的强化机理。通过SEM观察裂纹的萌生和扩展。结果表明，M / B双相可有效增强石墨-基体界面，抑制裂纹扩展，“白亮区”高碳马氏体尖端是另一个容易在压力下产生裂纹的部位。对于相-相界面的色淀，裂纹将一直延伸到“白亮区”和基体的整个界面。

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