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AlSi10Mg alloy modified with 4 wt.% cerium was fabricated by selective laser melting and subjected to a T6 solutionizing (2 h at 535°C) and ageing (10 h at 160°C) heat treatment. Microstructure, precipitates and hardness of as-built and heat-treated samples were analysed. Results show that as-built samples contained a refined cellular-dendritic microstructure as well as Ce-containing precipitates at heat-affected zone (HAZ). After T6 heat treatment, cellular-dendritic microstructure converted to fine microstructure containing Si agglomerates and sub-micron Ce-containing precipitates, while precipitates present in as-built HAZ underwent spheroidisation. Hardness testing showed that addition of Ce did not affect alloy hardness. However, the fine dispersion of Ce-containing precipitates and good coarsening resistance shows that Ce is a promising alloying element for the development of heat-resistant alloys. [ABSTRACT FROM AUTHOR]

Adhesions are an abnormal union of membranous surfaces. They are a painful and expensive consequence of abdominal surgeries, specifically in the peritoneal cavity. This complication requires a second surgery to remove the problem, known as adhesiolysis, which we are trying to avoid. Current solutions to adhesion formation either lack efficacy or induce an inflammatory response in the peritoneum. Our focus is to develop a post-surgical adhesion prevention polyelectrolyte complex (PEC) film, composed of an optimal ratio of chitosan (Chi) and polygalacturonic acid (PgA) to prevent adhesion formation. Adhesive properties of fibroblasts and macrophages on the PEC were also studied, since both cell types play a central role in the adhesion formation process. Additionally, we examined PEC attachment methods, ultimately for in vivo application. Current in vitro studies evaluated the material properties of the film to determine the stability of the material. The results of our studies identified certain ratios of Chi-PgA films which are mechanically consistent for use as intra-peritoneal barriers. Furthermore, their potential as anti-adhesive barriers were further supported by the fact that their surfaces are non-permissive for viable fibroblast and macrophage attachment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Machine learning helps establish LPBF processing window for TiCN/AlSi10Mg composite. • Within the new window, the properties of the fabricated composites are tailorable. • Increased laser power/scan speed resulted in the coarsening of Si network. • Lower yield strength and higher elongation were caused by coarsening of Si network. A Gaussian process regression-based machine learning approach was used to establish a processing window optimized for high density additive manufacturing of a 2 vol% TiCN reinforced AlSi10Mg composite by laser powder bed fusion. The optimized window for TiCN reinforced AlSi10Mg was found to be smaller than for AlSi10Mg. Within the optimized window, it was found that the Si eutectic cell size can be increased by raising the laser power/scanning speed at the constant energy density of 50 J/mm3 to control the tensile properties of the fabricated composites. [ABSTRACT FROM AUTHOR]

A high strength Al-5024 alloy containing Sc and Zr with a bi-modal microstructure consisting of fine equiaxed and coarse columnar grains was successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing. The formation of the bi-modal microstructure was mainly due to both the formation of primary Al 3 Sc precipitates that act as nucleation sites and the steep temperature gradient during LPBF. By simulating the thermal field of a single melt pool, the formation mechanism of the bi-modal microstructure was explained. It was found by simulation that a solidification interface velocity less than 110 mm/s was beneficial to the nucleation of Al 3 Sc precipitates and, hence, facilitated the formation of a fine grain microstructure. Applying different heat treatments revealed a trade-off trend between yield strength and ductility as a function of the heat treatment time, and a correlation in fatigue life and yield strength was observed, both of which were closely related to the status of the secondary Al 3 Sc precipitates. The highest ultimate tensile strength of 450 MPa and corresponding 107 cycle fatigue strength of 105 MPa were achieved after hot isostatic pressing for 4 h at 325 °C with 100 MPa pressure. Dynamic strain aging was found to occur in both as-built and some heat treated samples, which was related to magnesium (Mg) solute atom clustering attributed to: (i) the formation of a diffuse "Mg wall" due to the repetitive melting and rapid cooling in LPBF, and (ii) the growth of intragranular (Al 3 Sc) and intergranular precipitates (Fe-, Mn-rich) during subsequent heat treatment, thereby leading to an increasing number of misfit dislocations that promote the formation of Mg atom clusters. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a machine-learning approach based on Gaussian process regression was developed to identify the optimized processing window for laser powder bed fusion (LPBF). Using this method, we found a new and much larger optimized LPBF processing window than was known before for manufacturing fully dense AlSi10Mg samples (i.e., relative density ≥ 99%). The newly determined optimized processing parameters (e.g., laser power and scan speed) made it possible to achieve previously unattainable combinations of high strength and ductility. The results showed that although the AlSi10Mg specimens exhibited similar Al-Si eutectic microstructures (e.g., cell structures in fine and coarse grains), they displayed large difference in their mechanical properties including hardness (118 - 137 HV 10), ultimate tensile strength (297 - 389 MPa), elongation to failure (6.3 - 10.3%), and fracture toughness (9.9 - 12.7 kJ/m2). The underlying reason was attributed to the subtle microstructural differences that were further revealed using two newly defined morphology indices (i.e., dimensional-scale index I d and shape index I s) based on several key microstructural features obtained from scanning electron microscopy images. It was found that in addition to grain structure, the sub-grain cell size and cell boundary morphology of the LPBF fabricated AlSi10Mg also strongly affected the mechanical properties of the material. The method established in this study can be readily applied to the LPBF process optimization and mechanical properties manipulation of other widely used metals and alloys or newly designed materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]