Veile Georg, Regitz Elen, Smaga Marek, Weihe Stefan, Beck Tillmann
Materials Testing Institute, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany.
Insitute of Materials Science and Engineering, RPTU Kaiserslautern-Landau, Gottlieb-Daimler-Straße 47, 67663 Kaiserslautern, Germany.
Materials (Basel). 2024 Sep 16;17(18):4543. doi: 10.3390/ma17184543.
Due to variations in chemical composition and production processes, homonymous austenitic stainless steels can differ significantly regarding their initial microstructure, metastability, and thus, their fatigue behavior. Microstructural investigations and fatigue tests have been performed in order to evaluate this aspect. Three different batches and production forms of nominally one type of steel AISI 347 were investigated under monotonic tensile tests and cyclic loading under total strain and stress control in low and high cycle fatigue regimes, respectively. The deformation induced α'-martensite formation was investigated globally by means of in situ magnetic measurements and locally using optical light microscopy of color etching of micrographs. The investigation showed that the chemical composition and the different production processes influence the material behavior. In fatigue tests, a higher metastability and thus a higher level of deformation induced α'-martensite pronounced cyclic hardening, resulting in significantly greater endurable stresses in total strain-controlled tests and an increase in fatigue life in stress-controlled tests. For applications of non-destructive-testing, detailed knowledge of a component's metastability is required. In less metastable batches and for lower stress levels, α'-martensite primarily formed at the plasticization zone of a crack. Furthermore, the formation and nucleation points of α'-martensite were highly dependent on grain size and the presence of δ-ferrite. This study provides valuable insights into the different material behavior of three different batches with the same designation, i.e., AISI 347, due to different manufacturing processes and differences in the chemical composition, metastability, and microstructure.
由于化学成分和生产工艺的差异，同名奥氏体不锈钢在初始微观结构、亚稳定性以及疲劳行为方面可能存在显著差异。为了评估这一方面，已经进行了微观结构研究和疲劳试验。分别在单调拉伸试验以及低周疲劳和高周疲劳状态下的总应变和应力控制的循环加载条件下，对名义上为一种类型的AISI 347钢的三种不同批次和生产形式进行了研究。通过原位磁测量全局研究了变形诱导α'马氏体的形成，并使用金相彩色蚀刻光学显微镜局部研究了该形成。研究表明，化学成分和不同的生产工艺会影响材料性能。在疲劳试验中，较高的亚稳定性以及因此较高水平的变形诱导α'马氏体表现出循环硬化，在总应变控制试验中导致显著更高的持久应力，在应力控制试验中导致疲劳寿命增加。对于无损检测应用，需要详细了解部件的亚稳定性。在亚稳定性较低的批次中以及对于较低应力水平，α'马氏体主要在裂纹的塑化区形成。此外，α'马氏体的形成和成核点高度依赖于晶粒尺寸和δ铁素体的存在。本研究提供了宝贵的见解，以了解由于不同制造工艺以及化学成分、亚稳定性和微观结构差异，具有相同名称即AISI 347的三种不同批次的不同材料性能。
