Fracture toughness of quasicrystalline phase-former aluminum alloy fabricated by additive manufacturing

Abstract

The DEMa/UFSCar research group has recently shown that it is possible to obtain metastable quasicrystalline phase in large-volume parts of Al-Fe-Cr-Ti alloys manufactured by Laser Powder Bed Fusion (L-PBF). These alloys are promising for applications such as dies and structural parts because they have high specific strength and wear resistance, especially for high-temperature applications. These alloys are expected to have high fracture toughness due to a microstructure that combines the presence of a high-strength quasicrystalline phase with spherical morphology in a very refined ductile aluminum dendritic matrix due to the high cooling rates involved in the L-PBF process (as high as 105 K/s). Fracture toughness tests have never been performed before for these alloys because it was not possible to obtain large-volume parts of these alloys with the correct dimensions for this test through traditional manufacturing routes. The present project aims to investigate the fracture toughness of Al-Fe-Cr-Ti alloy fabricated by L-PBF. First, the L-PBF process parameters will be optimized to obtain the best combination of parameters to produce high-density samples with fewer structural defects. This optimized parameter combination will be used to produce specimens for CTOD fracture toughness tests under the ASTM E1290 standard. These specimens will be manufactured in different building directions (0, 45 e 90º) to investigate the influence of this parameter on the fracture toughness of the parts. The specimens will then be machined for notch formation, and fatigue testing will be performed for pre-crack generation. The microstructure and phase formation of these samples will be evaluated by optical and scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). In the end, the microstructure and phase formation, fracture toughness, and process parameters will be correlated to better understand these parameters' influence on this property.