Speaker: Dr. Juan Guillermo Santos Macias

Abstract

The development of additive manufacturing (AM) is opening new possibilities and new fields of application. The use of AM structural parts is already a reality in some cases. However, when aiming at high end and demanding sectors, such as the aeronautic and aerospace industries, in the instances where the structural aspect plays a critical role, the use of metal AM components is still limited. AM parts often have defects (porosity and roughness) that influence fatigue resistance in a negative way. There is a need to get rid of these defects typical of the AM technology. Efforts to achieve this can consist on AM manufacturing parameters optimisation. These parameters can be tuned to reduce roughness, but subsurface porosity is created at the same time, reducing the potential influence of the former type of defect but increasing that of the latter. In this research the post-treatment route was explored to investigate and tackle the fatigue resistance issue. A representative material, laser powder bed fusion AlSi10Mg, was used. As built samples were subjected to the following post-treatments: Stress relief heat treatment (SRHT), hot isostatic pressing (HIP) and friction stir processing (FSP). The first is a thermal treatment and the other two are thermomechanical. Through tensile-tensile fatigue testing to obtain SN or Wöhler curves and fatigue crack propagation testing a thorough study of the fatigue behaviour of the material in the different states was performed. Quantitatively, in contrast with the SRHT and HIP, that showed no significant improvement, an increase of up to 100 times in fatigue life was achieved with FSP. The reason behind these differences seems to be linked mainly to the porosity reduction effect of FSP, which makes it a promising post-processing technique to improve fatigue resistance.

Biography

Juan Guillermo Santos Macías is a PhD student (Project entitled “Surface mechanical treatment by friction stir processing of additive manufactured aluminium alloy parts to improve mechanical behaviour”) in the Institute of Mechanics, Materials and Civil Engineering at UCLouvain (Belgium). His interests revolve around the study of microstructure and mechanical behaviour of materials and their interrelationship. In particular, he has studied in detail the damage and fatigue performance of additive manufactured aluminium alloys, notably making use of synchrotron X-ray tomography for these purposes. He completed civil engineering studies with a specialisation in materials at the Universidad Carlos III de Madrid (Spain) and carried out his master thesis (Entitled “Influence of the grain size and phase content on the mechanical behaviour of magnesium alloys. Gravity casting and SPS manufactured”) at KULeuven (Belgium).