Awd Mustafa, Tenkamp Jochen, Hirtler Markus, Siddique Shafaqat, Bambach Markus, Walther Frank
Department of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
Chair of Mechanical Design and Manufacturing (KuF), BTU Cottbus-Senftenberg, 03046 Cottbus, Germany.
Materials (Basel). 2017 Dec 23;11(1):17. doi: 10.3390/ma11010017.
The second-generation aluminum-magnesium-scandium (Al-Mg-Sc) alloy, which is often referred to as Scalmalloy, has been developed as a high-strength aluminum alloy for selective laser melting (SLM). The high-cooling rates of melt pools during SLM establishes the thermodynamic conditions for a fine-grained crack-free aluminum structure saturated with fine precipitates of the ceramic phase Al₃-Sc. The precipitation allows tensile and fatigue strength of Scalmalloy to exceed those of AlSi10Mg by ~70%. Knowledge about properties of other additive manufacturing processes with slower cooling rates is currently not available. In this study, two batches of Scalmalloy processed by SLM and laser metal deposition (LMD) are compared regarding microstructure-induced properties. Microstructural strengthening mechanisms behind enhanced strength and ductility are investigated by scanning electron microscopy (SEM). Fatigue damage mechanisms in low-cycle (LCF) to high-cycle fatigue (HCF) are a subject of study in a combined strategy of experimental and statistical modeling for calculation of Woehler curves in the respective regimes. Modeling efforts are supported by non-destructive defect characterization in an X-ray computed tomography (µ-CT) platform. The investigations show that Scalmalloy specimens produced by LMD are prone to extensive porosity, contrary to SLM specimens, which is translated to ~30% lower fatigue strength.
第二代铝镁钪（Al-Mg-Sc）合金，通常被称为Scalmalloy，已被开发用作一种用于选择性激光熔化（SLM）的高强度铝合金。在SLM过程中熔池的高冷却速率为形成一种细晶粒、无裂纹且饱和了陶瓷相Al₃-Sc细小析出物的铝结构建立了热力学条件。这种析出使得Scalmalloy的拉伸强度和疲劳强度比AlSi10Mg高出约70%。目前还没有关于其他冷却速率较慢的增材制造工艺性能的相关知识。在本研究中，对通过SLM和激光金属沉积（LMD）加工的两批Scalmalloy的微观结构诱导性能进行了比较。通过扫描电子显微镜（SEM）研究了强度和延展性增强背后的微观结构强化机制。低周疲劳（LCF）至高周疲劳（HCF）中的疲劳损伤机制是采用实验和统计建模相结合的策略进行研究的主题，用于计算各自工况下的韦勒曲线。在X射线计算机断层扫描（µ-CT）平台上进行的无损缺陷表征为建模工作提供了支持。研究表明，与SLM试样相反，LMD生产的Scalmalloy试样容易出现大量孔隙，这导致疲劳强度降低约30%。
