Preparation of Nano/Micro Bimodal Aluminum Powder by Electrical Explosion of Wires

Electrical explosion of aluminum wires has been shown to be a versatile method for the preparation of bimodal nano/micro powders. The energy input into the wire has been found to determine the relative content of fine and coarse particles in bimodal aluminum powders. The use of aluminum bimodal powders has been shown to be promising for the development of high flowability feedstocks for metal injection molding and material extrusion additive manufacturing.

Mechanical Properties of Lightweight Foamed Concrete Reinforced with Raw Mesocarp Fibre

Lightweight foamed concrete (LFC) is recognised for its high flowability, minimal utilization of aggregates and superior heat insulation properties. LFC is excellent under compression but poor in tensile stress, as it produces multiple microcracks. LFC cannot withstand the tensile stress induced by applied forces without additional reinforcing elements. Hence, this study was conducted to examine the potential utilisation of oil palm mesocarp fibre (OPMF) reinforced LFC in terms of its mechanical properties. Two densities, 600kg/m3 and 1200kg/m3, were cast and tested with six different percentages of OPMF, which were 0.15%, 0.30%, 0.45% and 0.60%. The parameters evaluated were compressive strength, flexural strength and tensile strength. The results revealed that the inclusion of 0.45% of OPMF in LFC helps to give the best results for the compressive strength, flexural strength and splitting tensile strength. The OPMF facilitated to evade the promulgation of cracks in the plastic state in the cement matrix when the load was applied

Comparison of Flowability and Sinterability Among Different Binder Jetting Feedstock Powders: Nanopowder, Micropowder, and Granulated Powder

Feedstock powders used in binder jetting additive manufacturing include nanopowder, micropowder, and granulated powder. Two important characteristics of the feedstock powders are flowability and sinterability. This paper aims to compare the flowability and sinterability of different feedstock powders. Three powders were compared: nanopowder (with a particle size of ∼100 nm), micropowder (with a particle size of 70 μm), and granulated powder (with a granule size of ∼70 μm) made from the nanopowder by spray freeze drying. Flowability metrics employed included apparent density (AD), tap density (TD), volumetric flow rate (VFR), mass flow rate (MFR), Hausner ratio (HR), Carr index (CI), and repose angle (RA). Sinterability metrics employed included sintered bulk density (SBD), volumetric shrinkage (VS), and densification ratio (DR). Results show that the granulated powder has a higher flowability than the nanopowder and a higher sinterability than the micropowder. Moreover, different flowability metric values of the granulated powder are close to those of the micropowder, indicating that these two powers have a comparably high flowability. Similarly, different sinterability metric values of the granulated powder are close to those of the nanopowder, indicating that these two powders have a comparably high sinterability.

Research on the Mixture Ratio Test for Rubble-Built Structure Mortar Filling Construction Technology

Traditionally the rubble-built structures are constructed manually with low efficiency and long time consuming. It is studied in this research that the rubble-built structures are constructed with models according to designed profile. Firstly, the natural stones are piled up inside the model and then filled with self-compacting mortar into the inter-space of the stones at certain flow rate, and at last the models are removed after the mortar get hardened, so as to form the rubble-built structures with fast and mechanical construction process. The water and cement-sand mixture ratio for this construction process shall satisfy high flowability for flowing into the gaps of stones and also ensure the compressive strength of the structure. An indoor triangle box filling test is carried out to prove that the designed mixture ratio for filling the rubble-built structure is feasible and to determine the optimized mortar proportioning ratio.

Effect of Manufacturing Process of Master Alloy Powders on Homogeneity of Sintered Ti-5Al-1Fe by Blended Elemental Powder Metallurgy

To narrow down the candidates of the alloying element powders for Ti-5Al-1Fe products manufactured with BE/PM, two master alloy powders, atomized spherical 5Al-1Fe and crushed-andground polyhedron 5Al-1Fe-4Ti ternary powders, were investigated with emphasizing on homogeneity of alloying elements, Al and Fe, in sintered Ti-5Al-1Fe. Intense Al segregation is recognized in the sintered specimen manufactured using 5Al-1Fe atomized powders, while strong segregation is not observed in the specimen manufactured using 5Al-1Fe-4Ti crushed-and-ground powders. Density of sintered specimen manufactured using 5Al-1Fe atomized powders is lower than that manufactured using 5Al-1Fe-4Ti crushed-and-ground powders. Al segregation and lower sintered density are probably caused by lower density of the powder substance, high flowability of spherical powders and phase constitutions some of which have low melting points. Those factors have to be taken into account to manufacture sintered titanium alloys with high homogeneity by BE/PM.

PHYSICAL PROPERTIES OF SLAGS OF CaO – SiO2 – B2O3 SYSTEM CONTAINING 15 % OF Al2O3 AND 8 % OF MgO

Influence of the chemical composition of CaO – SiO2 – B2O3 oxide system containing 15 % Al2O3 and 8 % MgO (in this expression and hereinafter indicated by mass %) on viscosity and crystallization temperature was studied using experiment method of simplex lattice planning. Addition of B2O3 to the slags of oxide system expands the range of slags composition with a low crystallization temperature and viscosity. Slags with a basicity of 2 – 3, containing 1 – 3 % of B2O3 are characterized by a low crystallization temperature, varying from 1400 to 1450 °С and have high flowability. The viscosity of such slags when heated to 1550 and 1600 °C does not exceed 0.20 and 0.15 Pa·s, respectively. An increase in B2O3 content to 4 – 6 % in slags with a basicity of 2 – 3 is accompanied by a decrease in crystallization temperature to 1350 – 1425 °C with keeping low, not more than 0.15 Pa·s, viscosity in the range of heating temperatures at 1550 and 1600 °C. The displacement of formed slags containing 1 – 6 % of B2O3 to the area of increased basicity up to 3 – 5 preserves their relatively high fluidity. In this case, with an increase in B2O3 concentration, there is a clear tendency for the studied oxide system to shift to the region of low crystallization temperatures. Crystallization temperature of slags with basicity of 3 – 4 containing 6 % of B2O3 reaches 1400 °С and practically does not exceed 1475 °С of slags with basicity of 4 – 5 containing 1 – 2 % of B2O3 . At temperature of 1600 °C, the viscosity of such slags varies from 0.15 Pa·s with a basicity of 3 and a content of 5 – 6 % of B2O3 to 0.25 Pa·s in the basicity range of 4 – 5 with B2O3 content of 1 – 3 %. A decrease in temperature of the studied oxide system by 50 °C is accompanied by a slight (no more than 0.05 Pa·s) increase in viscosity.

Development of Pore-Free Ti-Si-C MAX/Al-Si Composite Materials Manufactured by Squeeze Casting Infiltration

Open-porous MAX phase skeletons from Ti3SiC2 were manufactured by Microwave-Assisted Self-propagating High-temperature Synthesis (MASHS) and subsequently subjected to squeeze casting infiltration with an Al-Si lightweight casting alloy (EN AC-44200). This alloy was chosen due to its high flowability, corrosion resistance and good machinability. The manufactured composites, together with a reference sample of the original alloy, underwent testing of thermal properties, including thermal conductivity and diffusivity, specific heat and thermal expansion in the temperature range 50-500 °C, which corresponds to the expected working temperatures of the material. The fabricated AlSi/Ti3SiC2 composites have significantly increased thermal stability, with coefficients of thermal expansion (approximately 10-11 × 10−6 °C−1) half that of the original alloy. As regards mechanical properties, the instrumental Young’s modulus and Vickers hardness of the composite materials are 170.8 and 8.5 GPa, respectively. Moreover, the microstructure and phase composition, structural defects and potential impacts between constituents of the manufactured composites were characterized using SEM, TEM and STEM microscopy and EDS and XRD analysis.

Binder Jetting Additive Manufacturing of Ceramics: Comparison of Flowability and Sinterability Between Raw and Granulated Powders

The objective of this study is to compare three different feedstock powders for the binder jetting process by characterizing their flowability and sinterability. Binder jetting additive manufacturing is a promising technology for fabricating ceramic parts with complex or customized geometries. Granulation is a promising material preparation method due to the potential high sinterability and flowability of the produced powder. However, no study has been made to systematically compare raw and granulated powders in terms of their flowing and sintering behaviors. This paper aims at filling this knowledge gap. Two raw powders (i.e., fine raw powder of 300 nm and coarse raw powder of 70 μm) and one granulated powder from spray freeze drying were compared. Different flowability metrics, including volumetric flow rate, mass flow rate, Hausner ratio, Carr index, and repose angle were measured. Different sinterability metrics, including sintered bulk density, volume shrinkage, and densification ratio were compared for all three powders. Results show that granulated powder achieved comparably high flowability to that of the coarse raw powder and also comparably high sinterability to that of the fine raw powder. Moreover, suitable metrics for the characterization of the sinterability and flowability for these three powders are recommended. This study suggests spray freeze drying produces high-quality feedstock powder for binder jetting process.