Understanding contribution of microstructure to fracture behaviour of sintered steels
Understanding contribution of microstructure to fracture behaviour of sintered steels
复制标题
了解微观结构对烧结钢断裂行为的贡献
DOI：
10.1179/1743290114y.0000000119
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发表时间：
2014
影响因子：
1.4
通讯作者：
Mónica Campos
中科院分区：
文献类型：
--
作者：
J. M. Torralba;L. Esteban;E. Bernardo;Mónica Campos
烧结钢的微观结构特征，包括相和孔隙率，强烈地制约着材料在使用条件下的机械行为。由于更好地理解组织与性能之间的关系是改善当前粉末冶金（PM）钢的关键，因此许多研究活动都在处理这种关系。到目前为止，已成功地应用于这一目的的断口分析后测试，最近，通过显微组织以及一些先进的计算机辅助工具的裂纹演化的原位分析。然而，仍然缺乏关于这些钢的局部微观结构在微观尺度上的局部机械行为和应变分布的信息，即在非均质PM微观结构中的哪些相有助于塑性变形的局部化，或者哪些相可以在加载过程中阻碍裂纹扩展。在目前的工作中，这些问题是通过三种技术的组合来解决的：（一）原位拉伸试验（在SEM中进行），以监测裂纹的萌生和扩展;（二）数字图像相关技术，以跟踪加载过程中的局部应变分布的进展;（三）加载样品的断口检查。三种粉末冶金钢，都从商业上可获得的粉末，但呈现不同的显微组织，进行了检查：铁素体-珠光体Fe-C钢，贝氏体预合金化Fe-Mo-C钢和扩散合金化Fe-Ni-Cu-Mo-C钢，具有更不均匀的显微组织（铁素体，珠光体，上和下贝氏体，马氏体和富Ni奥氏体）。
Microstructural features of sintered steels, which comprise both phases and porosity, strongly condition the mechanical behaviour of the material under service conditions. Many research activities have dealt with this relationship since better understanding of the microstructure–property correlation is the key of improvement of current powder metallurgy (PM) steels. Up to now, fractographic investigation after testing has been successfully applied for this purpose and, more recently, the in situ analysis of crack evolution through the microstructure as well as some advanced computer assisted tools. However, there is still a lack of information about local mechanical behaviour and strain distributions at the microscale in relation to the local microstructure of these steels, i.e. which phases in heterogeneous PM microstructures contribute to localisation of plastic deformation or which phases can impede crack propagation during loading. In the present work, these questions are addressed through the combination of three techniques: (i) in situ tensile testing (performed in the SEM) to monitor crack initiation and propagation; (ii) digital image correlation technique to trace the progress of local strain distributions during loading; (iii) fractographic examination of the loaded samples. Three PM steels, all obtained from commercially available powders but presenting different microstructures, are examined: a ferritic–pearlitic Fe–C steel, a bainitic prealloyed Fe–Mo–C steel and a diffusion alloyed Fe–Ni–Cu–Mo–C steel, with more heterogeneous microstructure (ferrite, pearlite, upper and lower bainite, martensite and Ni rich austenite).