High-temperature mechanical properties of cast Al–Si–Cu–Mg alloy by combined additions of cerium and zirconium

The main aim of this work is to investigate the effects of combinative Ce and Zr additions (0.3 wt% Ce+0.16 wt% Zr; 0.3 wt% Ce+0.27 wt% Zr and 0.3 wt% Ce+0.36 wt% Zr) on the microstructure and mechanical properties in cast Al–Si–Cu–Mgalloy. The microstructures features were investigated by optical microscope, scanning electron microscope and hardness measurements. The microstructural analysis has shown that the increase of Ce and Zr contents increases the volume fraction of intermetallics formed during the solidification leading to grain refinement and changes in silicon morphology of the as-cast microstructure. The intermetallics formed do not dissolve during the solution heating treatment (T6). The mechanical behavior at room and high temperatures (175, 210, 245 and 275 °C) was determined from uniaxial tensile tests. The high thermal stability of Al–Si– Cu–La–Ce and Al–Si–Zr–Ti–Mgphases found in microstructure, in particular for the alloy containing 0.3 wt% Ce+0.27 wt% Zr, is responsible for the increase to 6.7% and 5.1% the ultimate strength at 210 °Cand 275 °Crespectively, compared with the standard alloy

Comparative study between crack tip opening displacement techniques by statistical analysis

Standardized tests may not always achieve all their analytical objectives. Particularly to structural integrity, where a reproduction of the practical occurrences of the industry is desired, new techniques are being developed. Therefore, this work aims at evaluating fracture toughness in tensile armour through four measurement methodologies (standard, video, laser and stretch zone (SZ)) to obtain crack tip opening displacement (CTOD), and compares their responses by ANOVA and Duncan’s tests. The findings showed equivalence between the standard and other approaches, thus allowing distinct methods for fracture toughness evaluation

Towards qualification of friction stir welding to AA5083-O and AA5052-O aluminum alloys

Friction Stir Welding (FSW) is an excellent alternative for joining dissimilar and similar materials in comparison to conventional welding processes. In this sense, this work aims at qualifying FSW to similar AA5083-O and AA5052-O aluminum alloys, with 6.35 mm thickness, in a CNC machining center. Therefore, four welding experiments were undertaken. At first, two types of plate surface finish were considered before joining. Afterward, two tool probe geometries, and changes in the base material position were evaluated. Hence, the welds were mainly analyzed by metallography, tensile testing, and bending tests. Results showed that the machining step to oxides removal and plates alignment is beneficial for the weld processing and the factor that has significant influence to achieve suitable joints is the tool probe geometry. Finally, by obtaining an average ultimate tensile strength (UTS) of around 191 MPa, enhanced microhardness, and bent angle of approximately 150°, the best joint was chosen

Probing underlying mechanisms for PCBN tool decay during friction stir welding of nickel-based alloys

Friction stir welding (FSW) of nickel-based alloys can provide joints with improved corrosion resistance and mechanical properties that are deteriorated significantly during fusion welding of these alloys. However, rapid wear and poor longevity of tools are major concerns for FSW of nickel-based alloys. Polycrystalline cubic Boron Nitride (pcBN) has emerged as an alternative tool material due to its enhanced strength and stiffness but its use for FSW of nickel-based alloys is rarely explored. An investigation is therefore undertaken to examine FSW of Inconel 625, which is a commonly used nickel-based alloy, by experimental investigation and computational process modelling. The potential failure mechanisms of pcBN tools during FSW of Inconel 625 are examined. The results showed that the thermal softening of the tungstenrhenium binder phase and dissolution of tungsten into Inconel 625 are potential mechanisms to early wear and failure of the pcBN tools for FSW of Inconel 625

Feasibility of orbital friction stir welding on clad pipes of API X65 steel and Inconel 625

Orbital friction stir welding (FSW) has been applied to clad pipes, which is certainly of interest to the oil and gas industry. In this context, an FSW system capable of performing sound joints in one pass with full tool penetration was developed. Orbital FSW was executed in 6 mm thick API X65 PSL2 steel clad pipes with 3 mm thick Inconel 625 using a polycrystalline cubic boron nitride (pcBN) tool. The metallurgical and mechanical properties of the joints were investigated. Sound joints with axial forces of 45–50 kN, tool rotational speeds of 400–500 rpm, and a welding speed of 2 mm/s were obtained, illustrating that the developed system can perform FSW joints without volumetric defects

Mitigating the susceptibility to intergranular corrosion of alloy 625 by friction‑stir welding

In this work, friction-stir welding (FSW) was employed to alloy 625 grade I (soft annealed) sheets. Therefore, solid-state based welding was undertaken with a tool rotational speed of 200 rpm and a welding speed of 1 mm/s. Microstructural features were analyzed by light optical and scanning electron microscopy (LOM and SEM). Moreover, microhardness measurements were performed. The susceptibility to intergranular corrosion was verifed by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. Complementary, intergranular corrosion was also evaluated by the ASTM G28 Method A. FSW promoted grain refnement, increased microhardness, and reduction in the degree of sensitization. Finally, the mean corrosion rate observed in the ASTM G28 Method A test was 0.4406 mm/year, which suggests a good weld quality

Residual stress evaluation in friction stir welds of inconel 625

A utilização de materiais nobres é requisito básico em aplicações onde existe um ambiente agressivo como na indústria do petróleo e nuclear. Neste panorama, a liga Inconel 625 é frequentemente utilizada como material de cladeamento no revestimento interno de dutos rígidos. Assim, as superligas de níquel exercem papel fundamental nos campos de exploração de águas profundas e, por isso, o conhecimento de métodos modernos de soldagem aplicados a estas ligas e suas consequências nos estados de tensões residuais é importante. Portanto, o presente trabalho faz uma avaliação das tensões residuais após a Soldagem por Fricção e Mistura Mecânica (SFMM) em chapas soldadas de Inconel 625. A união das chapas foi realizada com rotação da ferramenta 200 e 1200 rpm e velocidade de soldagem constante (1mm/s). As medições de tensões residuais na superfície das juntas soldadas foram investigadas através da técnica de difração de raios-X. Além disso, foram avaliadas as macroestruturas e o aporte térmico de acordo com os parâmetros de soldagem empregados. Embora não existam muitos trabalhos relacionados ao processo SFMM para ligas de Inconel, provavelmente devido à sua dificuldade de soldagem, tem sido percebido um aumento na aplicação da soldagem no estado sólido como excelente alternativa para as superligas à base de níquel. Os resultados mostraram que diferentes parâmetros de processo produziram juntas soldadas distintas e, consequentemente, variações na distribuição de tensões residuais. Por fim, um aumento na velocidade de rotação da ferramenta ocasionou um aumento nas tensões residuais na zona de mistura.The use of noble materials is a basic requirement in applications where an aggressive environment such as offshore industry and nuclear energy. In this scenario, the Inconel 625 is often used as clad material in rigid pipes. Thus, nickel superalloys play a fundamental role in the deepwater exploration fields and, therefore, understanding of modern welding methods applied to these alloys and their consequences in the residual stress states is very important. Hence, this work evaluates the residual stress distributions after Friction Stir Welding (FSW) applied on Inconel 625 sheets. FSW was performed with tool rotational speed in the range of 200 to 1200 rpm and welding speed constant. Measurements of superficial residual stresses were investigated by X-ray Diffraction. In addition, macrostructures and heat input were evaluated. Although there are only few reports related to FSW applied on Inconel alloys, probably due to this welding process difficulty, it has been regarded that there is cumulative application of a solid state welding as an excellent alternative for nickel superalloys. The results showed that different welding parameters produced distinctly welded joints and consequently changes in the residual stress distributions. Finally, an increase in the tool rotation speed increased the residual stress in the stir zone

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio