Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures
Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures
复制标题
DOI：
10.1016/j.msea.2018.06.063
复制
发表时间：
2018-09-12
期刊：
影响因子：
6.4
通讯作者：
Jepson, Mark A. E.
中科院分区：
文献类型：
--
作者：
Benaarbia, A.;Xu, X.;Jepson, Mark A. E.
本文报道了一种MarBN钢在高温下的短期蠕变行为。在625℃、650℃和675℃3种不同温度下进行蠕变试验，外加应力范围为160 ~ 300 MPa，失效时间为1 ~ 350 h。宏观蠕变数据分析表明，稳态蠕变表现为幂律应力依赖，其指数为7，活化能为307 kJ mol(-1)，表明位错爬升是MarBN钢主要的速率控制蠕变机制。宏观塑性失稳也被观察到，在断裂区域有明显的颈缩。所有的宏观预测都与微观结构数据相结合，从蠕变破裂样品的检查中推断，以建立宏观特征（颈缩，损伤等）与潜在的微观结构机制之间的关系。对断裂表面的分析显示出韧性断裂模式。电子背散射衍射（EBSD）分析表明，在断裂表面附近，原始马氏体亚结构发生了明显的变形和细化，这是长程塑性流动的证据。在亚结构边界附近也观察到位错堆积和缠结现象。所有这些微观结构观察表明，蠕变是由微观结构的几个元素之间的复杂相互作用，如位错，沉淀和组织边界的影响。计算得到的应力指数和活化能在定量上与突出的微观结构特征一致，与实际观察到的蠕变微观结构有一定的关系。
This paper reports the short-term creep behaviour at elevated temperatures of a MarBN steel variant. Creep tests were performed at three different temperatures (625 degrees C, 650 degrees C and 675 degrees C) with applied stresses ranging from 160 MPa to 300 MPa, and failure times from 1 to 350 h. Analysis of the macroscopic creep data indicates that the steady-state creep exhibits a power-law stress dependence with an exponent of 7 and an activation energy of 307 kJ mol(-1), suggesting that dislocation climb is the dominant rate-controlling creep mechanism for MarBN steel. Macroscopic plastic instability has also been observed, highlighted by an obvious necking at the rupture region. All the macroscopic predictions have been combined with microstructural data, inferred from an examination of creep ruptured samples, to build up relations between macroscopic features (necking, damage, etc.), and underlying microstructural mechanisms. Analysis of the rupture surfaces has revealed a ductile fracture mode. Electron Backscatter Diffraction (EBSD) analysis near to the rupture surface has indicated significant distortion and refinement of the original martensitic substructure, which is evidence of long-range plastic flow. Dislocation pile-ups and tangles from TEM were also observed near substructure boundaries and precipitate particles. All of these microstructural observations suggest that creep is influenced by a complex interaction between several elements of the microstructure, such as dislocations, precipitates and structure boundaries. The calculated stress exponent and activation energy have been found to agree quantitatively with the highlighted microstructural features, bearing some relationships to the true observed creep microstructures.