Understanding damage evolution in silicon-molybdenum alloyed cast iron through 3D imaging on multiple length scales

Ductile cast irons (DCI) alloyed with silicon and molybdenum (high SiMo-alloys) are commonly used in engine components where materials that can withstand harsh conditions are needed, e.g., in manifolds of the exhaust systems. However, for a detailed understanding of the micromechanical behavior of the materials, an in-situ 3D approach is needed. Here we propose a methodology combining digital volume correlation based on x-ray tomography with line beam and scanning 3DXRD. This combination of techniques will allow us to study intragranular variation of strain and orientation, follow grains even after yield, and obtain information on the shapes and sizes of the grains in the material. This also makes it possible to extract local stress-strain curves from different regions of the sample. Such information will be very useful in understanding the micromechanics of the materials, in terms of e.g. yielding behavior, and can also be used to calibrate numerical material models.

合金化硅与钼的球墨铸铁（DCI，即高硅钼合金），常被应用于需要耐受严苛工况的发动机部件，例如排气系统歧管。但若要深入解析该材料的细观力学行为，则需采用原位三维表征方法。本文提出一种将基于线光束X射线断层扫描（X-ray tomography）的体数字相关（digital volume correlation）技术，与扫描三维X射线衍射（3DXRD）相结合的研究方法。该技术组合可实现多项研究目标：探究晶粒内应变与取向的变化规律，即便在材料发生屈服后仍可追踪晶粒，并获取材料内部晶粒的形状与尺寸信息。此外，该方法还能从试样的不同区域提取局部应力-应变曲线。此类信息对于理解材料的细观力学机制（如屈服行为）极具参考价值，同时也可用于校准数值材料模型。