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超细密ADI服役中的热力耦合效应及石墨球包覆层的观察
Investigation on Thermal-stress Coupling Effect and Transformation of the Layer Covered on Graphite Nodules in the Parts Made by ADI with Ultrafine Structure
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- DOI:
- 作者:
- 许旸 葛利玲 严富学 罗启文 蒋百灵 刘宝建 颜国君
XU Yang;GE Liling;YAN Fuxue;LUO Qiwen;JIANG Bailing;LIU Baojian;YAN Guojun
- 作者单位:
- 西安理工大学材料科学与工程学院
School of Materials Science and Engineering,Xi'an University of Technology,Xi'an 71004& China
- 关键词:
- ADI热力耦合效应 连续铸造 位错增殖
ADI the thermal-stress coupling effect continuous casting propagated dislocations
- 摘要:
- 初步观察和分析表明,球铁空心型材垂直连铸的共晶凝固过程中,石墨及奥氏体结晶时所放出的大量潜热在石墨球外层形成了数百纳米厚的混杂态包覆层。此包覆层集纳了铁液中的杂质原子和化合物颗粒,净化了基体成分。用这种球铁坯材,通过等温淬火获得的超细密ADI材料,在服役中经受小幅度弹性变形时,表现出明显的热力耦合效应,即把石墨球周围一圈基体转变成为"应变时效+热时效"复合组织。这种组织的硬度比淬火硬度稍有降低,但能有效抑制疲劳裂纹的萌生,这应来源于以石墨球为中心的高温温度场启动了增殖位错的自动消弭机制。Our preliminary observation and analysis had shown that a hybrid transition layer covered on the graphite nodules would be formed due to a great quantity of latent heat coming from the solidification of graphite and austenite in the process of producing hollow nodular cast iron profiles by the upwards continuous casting. The layer can purify the metallic matrix in the casts because a great deal of impurities and compounds, which were formerly distributed in the metallic matrix, were collected in the layer. The nodular cast iron profiles produced by the process can be quenched into ADI with an ultrafine structure by an isothermal quenching. When the parts made from the quenched profiles were in their course of working and suffered from an elastic deformation with a high frequency and low amplitude in, an obvious thermal-stress coupling effect would happen in them, that is, the quenched structure of metallic matrix around the graphite nodules were transformed into a "strain aging and thermal aging" complex structure. The hardness of the complex structure was slightly smaller than that of quenched structure, but the complex structure can inhibited obviously the initiation of cracks. These changes in the matrix may come from automatic elimination of propagated dislocations, which were activated by micro-regions temperature fields centered at graphite nodules.