Tensile and fatigue behaviors of additively manufactured F357 and AlSi10Mg alloys: Effects of manufacturing process and temperature

• Cryogenic to high temperature mechanical behavior of AM F357 and AlSi10Mg was studied. • Tensile strength of both alloys dropped sharply at 300 °C due to grain boundary sliding. • Cyclic plasticity mainly governed fatigue life at higher strain amplitudes at 21 °C. • At lower strains, fatigue-critical defect size controlled life across temperatures. This study investigated the temperature-dependent tensile and fatigue behaviors of F357 and AlSi10Mg produced via both laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED). Tensile and fully reversed strain-controlled fatigue tests were conducted from cryogenic to elevated temperatures to capture the mechanical response of these alloys under service-relevant thermal conditions and to examine the underlying temperature-dependent deformation and failure mechanisms. Tensile strength, with that of AlSi10Mg being higher, for both alloys gradually decreased by up to 30% from −195 to 200 °C due to increasing dislocation mobility. The higher Si content in AlSi10Mg promoted void nucleation through brittle Si particle fracture, resulting in up to 35% lower ductility than F357. At room temperature and higher strain amplitudes, F357 specimens exhibited up to 5 times shorter fatigue lives than AlSi10Mg ones, and L-PBF specimens indicated up to 3 times shorter lives than their LP-DED counterparts, which were attributed to the more frequent and earlier onset of crack initiations resulting from their enhanced cyclic plasticity. At lower strain levels, L-PBF specimens for both alloys demonstrated up to 7 times longer fatigue lives than LP-DED ones across all test temperatures due to their smaller crack-initiating volumetric defects.