Superior strength of tri-layered Al-Cu-Al nano-composites processed by high-pressure torsion

This investigation demonstrates that a solid-state reaction occurs by the application of high-pressure torsion (HPT) in the production of nanostructured multilayered hybrid Al-Cu systems. Three-layered stacks of Al/Cu/Al were subjected for up to 200 revolutions of HPT under an applied pressure of 6.0 GPa. Microstructural and mechanical properties analysis were carried out after HPT using X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectrometry (EDX), microhardness measurements and tensile tests. The SEM observations revealed the formation of a multi-nano-layered structure in the whole volume of the disks. Further investigations with the use of TEM demonstrated that each nano-layer consists of nano-grains having sizes of about 20 nm. Analysis by XRD and selected area electron diffraction (SAED) confirmed the formation of intermetallic CuAl2 and Cu9Al4 phases in the layered structures. The experiments also showed a significant improvement in microhardness (up to ~450 Hv) and tensile properties (over 900 MPa of UTS after 200 turns) when compared to both Al-1050 and 99.95%Cu alloys in the initial state and after HPT processing. The results demonstrate that HPT offers an outstanding opportunity for producing novel nanostructured Al-Cu multilayered composites having unique mechanical properties

Effect of applied pressure on microstructure development and homogeneity in an aluminium alloy processed by high-pressure torsion

An investigation was conducted to evaluate the influence of applied pressure on the processing of an aluminium 5483 alloy by high-pressure torsion (HPT). Discs were processed by HPT through 1/4 to 5 revolutions at room temperature using the two different applied pressures of 1.0 and 6.0 GPa. Samples were examined after HPT using microhardness measurements and transmission electron microscopy. Colour-coded maps were constructed to show the hardness distributions and the mechanical properties were evaluated by tensile testing. It is shown that the results are dependent upon the applied pressure such that a higher pressure enhances the accumulation of defects and leads to a more rapid grain refinement. The effect of pressure is especially visible in the early stages after fractional numbers of turns since the microstructure and properties tend to homogenize at high numbers of turns

Physicochemical Properties of Dentine Subjected to Microabrasive Blasting and Its Influence on Bonding to Self-Adhesive Prosthetic Cement in Shear Bond Strength Test: An In Vitro Study

The aim of this in vitro study was to assess the influence of microabrasive blasting on the physicochemical properties of dentine and shear bond strength (SBS) of self-adhesive resin cement (Maxcem Elite, Kerr, Orange, CA, USA) bonded to the dentine surface. Ninety cylindrical specimens with exposed dentine of human teeth were prepared and divided into three randomized, parallel sample sets A, B, and C. Groups B and C were subjected to abrasive blasting using a micro-sandblasting device (Microetcher IIa, Danville Materials, Carlsbad, CA, USA) with two gradations of Al2O3 abrasives (Group B, abrasion with a gradation of 50 μm; group C, abrasion with a gradation of 27 μm). SEM imaging, profilometry, chemical composition analysis, contact angle measurements, surface free energy, and SBS tests were performed. The resulting data were statistically analyzed using the Statistica software (ver. 13.3, Tibco Software Inc., Palo Alto, CA, USA). Microabrasive blasting caused changes in surface topography, structural features, and the connection strength between the dentin surface and self-adhesive prosthetic cement. Air microabrasion through the multifactorial positive reorganization of the treated surface of dentine is recommended as a pretreatment method in fixed prosthodontics adhesive cementation protocols

Mechanical Properties of Ti Grade 2 Manufactured Using Laser Beam Powder Bed Fusion (PBF-LB) with Checkerboard Laser Scanning and In Situ Oxygen Strengthening

Additive manufacturing (AM) technologies have advanced from rapid prototyping to becoming viable manufacturing solutions, offering users both design flexibility and mechanical properties that meet ISO/ASTM standards. Powder bed fusion using a laser beam (PBF-LB), a popular additive manufacturing process (aka 3D printing), is used for the cost-effective production of high-quality products for the medical, aviation, and automotive industries. Despite the growing variety of metallic powder materials available for the PBF-LB process, there is still a need for new materials and procedures to optimize the processing parameters before implementing them into the production stage. In this study, we explored the use of a checkerboard scanning strategy to create samples of various sizes (ranging from 130 mm3 to 8000 mm3 using parameters developed for a small 125 mm3 piece). During the PBF-LB process, all samples were fabricated using Ti grade 2 and were in situ alloyed with a precisely controlled amount of oxygen (0.1–0.4% vol.) to enhance their mechanical properties using a solid solution strengthening mechanism. The samples were fabricated in three sets: I. Different sizes and orientations, II. Different scanning strategies, and III. Rods for high-cycle fatigue (HCF). For the tensile tests, micro samples were cut using WEDM, while for the HCF tests, samples were machined to eliminate the influence of surface roughness on their mechanical performance. The amount of oxygen in the fabricated samples was at least 50% higher than in raw Ti grade 2 powder. The O2-enriched Ti produced in the PBF-LB process exhibited a tensile strength ranging from 399 ± 25 MPa to 752 ± 14 MPa, with outcomes varying based on the size of the object and the laser scanning strategy employed. The fatigue strength of PBF-LB fabricated Ti was 386 MPa, whereas the reference Ti grade 2 rod samples exhibited a fatigue strength of 312 MPa. Our study revealed that PBF-LB parameters optimized for small samples could be adapted to fabricate larger samples using checkerboard (“island”) scanning strategies. However, some additional process parameter changes are needed to reduce porosity