In situ structural analysis of AlSi10Mg for additive manufacturing – from powder to thermally treated parts

In situ STEM heating experiments allow us to characterize the process of laser melting-based 3D printing of metal alloys, their structure and elemental composition – from pristine printing powders to as-built structures and thermally treated materials.

Printing three-dimensional, robust metallic structures via laser beam melting of alloy powders is a rapidly growing industry branch. Manufacturers of such parts strive for optimizing their processes, not only to improve material properties, but also to enhance the interchangeability of building platforms and thus, their economic flexibility. However, the number of critical parameters for 3D printing is large and most simulations or macroscopic tests do not paint a broad enough picture about the outcome of a recipe. As-built samples from the same powder alloys but from different manufacturing batches with altered process parameters differ in mechanical properties due to the grade of intrinsic thermal treatment they experience in the respective laser-melting process. Differential scanning calorimetry (DSC) and X-ray diffraction are prominent techniques used to provide information on transitions and crystallinity in the material before and after additional treatments, but the results are often inconclusive with respect to morphological changes. Through in situ heating experiments in TEM, applying EDXS and EELS for structural and elemental analysis, we aim to bridge this gap. We therefore studied the micro- and nanostructure of an AlSi10Mg – a high-hardness lightweight alloy with well-known casting properties that is of great interest for additive manufacturing.