Few systematic studies on the correlation between alloy microstructure and mechanical failure of the AlSi10Mg alloy produced by laser-based powder bed fusion (L-PBF) are available in the literature. This work investigates the fracture mechanisms of the L-PBF AlSi10Mg alloy in as-built (AB) condition and after three different heat treatments (T5 (4 h at 160 °C), standard T6 (T6B) (1 h at 540 °C followed by 4 h at 160 °C), and rapid T6 (T6R) (10 min at 510 °C followed by 6 h at 160 °C)). In-situ tensile tests were conducted with scanning electron microscopy combined with electron backscattering diffraction. In all samples the crack nucleation was at defects. In AB and T5, the interconnected Si network fostered damage at low strain due to the formation of voids and the fragmentation of the Si phase. T6 heat treatment (T6B and T6R) formed a discrete globular Si morphology with less stress concentration, which delayed the void nucleation and growth in the Al matrix. The analysis empirically confirmed the higher ductility of the T6 microstructure than that of the AB and T5, highlighting the positive effects on the mechanical performance of the more homogeneous distribution of finer Si particles in T6R.

Cast aluminum alloys are widely used in the automotive field for the production of complex engine parts. However, the mechanical properties of heat-treatable alloys (e.g., Al–Si–Mg or Al–Si–Cu–Mg) are negatively affected by prolonged exposure to temperatures higher than about 200 °C. To date, several researchers have proposed the addition of alloying elements, such as Sc or Hf, for enhancing the high temperature behavior of cast Al alloys, while Mo has not been widely investigated. The present study aimed to assess the effects of Mo addition on microstructure, mechanical properties, and thermal stability of the A354 alloy. Samples of A354 alloy with different amount of Mo (in the range 0.1 to 0.8 wt %) were produced. The casting conditions and heat treatment parameters were optimized by means of optical and scanning electron microscopy, thermal analysis and hardness tests. Tensile tests highlighted that Mo induces a moderate increase of yield strength at room temperature (about 10%), but no appreciable improvement in the performance of the alloy at 250 °C was observed.

Plasma Electrolytic Oxidation (PEO) layers were produced on Ti-6Al-4V in different conditions, so as to assess the influence of layer structure, current mode, duty cycle and surface finishing on microstructural features and tribological behaviour. In DC regime, the double-layer structure (silicate bath followed by phosphate bath) beneficially affected wear resistance. In unipolar pulsed DC (phosphate bath), the wear resistance of single layers improved with increasing duty cycle, due to improved microstructure and adhesion: high duty cycle single layers can be considered an alternative to double-layer deposition. Surface finishing by abrasive blasting with spheroidal glass beads leads to surface roughness decrease and hence to decreased friction and improved wear resistance. The best-performing PEO layers showed promising results in the comparison with reference materials such as CoCrMo (both uncoated and (Ti,Nb)N PVD-coated) and PVD-coated Ti-6Al-4V up to 30 N normal load.

Al-Si-Cu alloys are the most widely used materials for high-pressure die casting processes. In such alloys, Fe content is generally high to avoid die soldering issues, but it is considered an impurity since it generates acicular intermetallics (β-Fe) which are detrimental to the mechanical behavior of the alloys. Mn and Cr may act as modifiers, leading to the formation of other Fe-bearing particles which are characterized by less harmful morphologies, and which tend to settle on the bottom of furnaces and crucibles (usually referred to as sludge). This work is aimed at evaluating the influence of sludge intermetallics on the fatigue behavior of A380 Al-Si-Cu alloy. Four alloys were produced by adding different Fe, Mn and Cr contents to A380 alloy; samples were remelted by directional solidification equipment to obtain a fixed secondary dendrite arm spacing (SDAS) value (~10 μm), then subjected to hot isostatic pressing (HIP). Rotating bending fatigue tests showed that, at room temperature, sludge particles play a detrimental role on fatigue behavior of T6 alloys, diminishing fatigue strength. At elevated temperatures (200 °C) and after overaging, the influence of sludge is less relevant, probably due to a softening of the α-Al matrix and a reduction of stress concentration related to Fe-bearing intermetallics.

The AlSi10Mg alloy produced by laser-based powder bed fusion (L-PBF) is widely used to produce high-value-added structural parts subjected to cyclic mechanical loads at high temperatures. The paper aims to widen the knowledge of the room- and high-temperature (200 °C) fatigue behavior of the L-PBF AlSi10Mg alloy by analyzing the fully reversed rotating bending test results on mechanically polished specimens. Two heat-treated conditions are analyzed: T5 (direct artificial aging: 4 h at 160 °C) and novel T6R (rapid solution: 10 min at 510 °C, artificial aging: 6 h at 160 °C). The study highlights that (i) the T6R alloy is characterized by higher fatigue strength at room (108 MPa) and high temperatures (92 MPa) than the T5 alloy (92 and 78 MPa, respectively); (ii) thermal exposure at 200 °C up to 17 h does not introduce macroscopical microstructural variation; (iii) fracture surfaces of the room- and high-temperature-tested specimens show comparable crack initiation, mostly from sub-superficial gas and keyhole pores, and failure propagation mechanisms. In conclusion, the L-PBF AlSi10Mg alloy offers good cyclic mechanical performances under various operating conditions, especially for the T6R alloy, and could be considered for structural components operating at temperatures up to 200 °C.