Microestructura y comportamiento mecánico de la aleación Ti-6AI-4V procesada mediante fabricación aditiva de lecho de polvo Electron Beam Melting

171 p.En este trabajo se han estudiado la relación de algunas variables de fabricación para la aleación de titanio Ti-6Al-4V fabricado por el proceso de fabricación aditiva electron beam melting (EBM) y las características y propiedades intrínsecas del material resultante. La microestructura propia, obtenida por el proceso EBM, ha sido modificada mediante tratamientos térmicos basados en tres enfoques estudiando el efecto de varias velocidades de enfriamiento después de un tratamiento de recocido ß, el efecto de la temperaturas y tiempos de recocido en los espesores de las láminas ¿, y de parámetros de envejecimiento, tiempo y temperatura, tras un proceso de solubilización y temple al agua. Se han establecido una serie de correlaciones que relacionan el espesor de la lámina ¿ y las propiedades mecánicas del material. Se ha desarrollado una comprensión fundamental de los mecanismos de crecimiento de grietas por fatiga en relación con la microestructura direccional del EBM Ti-6Al-4V. Para ello se ha estudiado la propagación de grietas en dirección paralela y perpendicular a la dirección de fabricación del proceso EBM, para diferentes relaciones de tensión y etapas del proceso de crecimiento de grietas. Se ha investigado la interacción entre la microestructura direccional EBM y se ha comparado con la interacción de la microestructura recocida ß equiaxial obtenida tras un recocido por encima de la temperatura ß transus. Finalmente, también se ha realizado una comparación de microestructura, propiedades mecánicas y propiedades de fatiga entre el proceso EBM y el proceso LMD para el material Ti-6Al-4V.Tecnali

Microstructure and Phase Formation of Novel Al80Mg5Sn5Zn5X5 Light-Weight Complex Concentrated Aluminum Alloys

In this work, three novel complex concentrated aluminum alloys were developed. To investigate the unexplored region of the multicomponent phase diagrams, thermo-physical parameters and the CALPHAD method were used to understand the phase formation of the Al80Mg5Sn5Zn5Ni5 , Al80Mg5Sn5Zn5Mn5 , and Al80Mg5Sn5Zn5Ti5 alloys. The ingots of the alloys were manufactured by a gravity permanent mold casting process, avoiding the use of expensive, dangerous, or scarce alloying elements. The microstructural evolution as a function of the variable element (Ni, Mn, or Ti) was studied by means of different microstructural characterization techniques. The hardness and compressive strength of the as-cast alloys at room temperature were studied and correlated with the previously characterized microstructures. All the alloys showed multiphase microstructures with major α-Al dendritic matrix reinforced with secondary phases. In terms of mechanical properties, the developed alloys exhibited a high compression yield strength up to 420 MPa, high compression fracture strength up to 563 MPa, and elongation greater than 12%.This research was funded by the Basque Government through the projects Elkartek: KK-2018/00015 (NEWHEA2) and KK-2020/00047 (CEMAP)

Research on Coatings and Infiltration to Strengthen Ceramic Lost Cores Used in High-Pressure Die Casting Processes

Lost cores used to manufacture complex aluminium components through high-pressure die casting (HPDC) processes need to withstand very high injection velocities and pressures. The conventional sand cores used in other casting processes, such as sand casting or low-pressure die casting, do not support the aggressive process parameters of the HPDC, so advanced ceramic cores must be used. These cores must be strong enough not to get broken during the casting process, but, at the same time, they must have a minimum porosity to be easily removed from the casting to obtain the finished part. Due to this porosity, the aluminium penetrates the core surface during the casting process. So, the criterion here is to find the necessary compromise between strength and porosity and to protect the core surface from the aluminium penetration. In this work, two research lines have been followed to address these challenges. On the one hand, different refractory coatings have been applied to the ceramic core surface with the aim of sealing it. Amongst the coatings analysed, boron nitride-based one has been found to be the most suitable and cost-effective solution to avoid aluminium penetration. On the other hand, silica has been proved to be a suitable infiltration agent to increase the strength of the core.This work has been carried out under the framework of the CORE 4.0 project funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement no 701197. The authors wish to show their gratitude to Rauschert Italia for manufacturing the ceramic cores and the bars, Edertek for helping with the die casting trials and machining of the samples and FerroCˇrtalicˇ for making the de-coring tests

Gas Blowing Ultrasonic Aluminium Degassing Assessment with the Reduced Pressure Test (RPT) Method

Entrapped gases, solidification shrinkage and non-metallic compound formation are main sources of porosity in aluminium alloy castings. Porosity is detrimental to the mechanical properties of these castings; therefore, its reduction is pursued. Rotary degassing is the method mostly employed in industry to remove dissolved gases from aluminium melts, reducing porosity formation during solidification of the cast part. Recently, ultrasonic degassing has emerged as a promising alternative thanks to a lower dross formation and higher energy efficiency. This work aims to evaluate the efficiency of the ultrasonic degasser and compare it to a conventional rotary degassing technique applied to an AlSi10Mg alloy. Degassing efficiency was evaluated employing the reduced pressure test (RPT), where samples solidified under reduced pressure conditions are analysed. Factors affecting RPT were considered and temperature parameters for the test were established. The influence of ultrasonic degassing process parameters, such as degassing treatment duration and purging gas flow rate were studied, as well as treated aluminium volume and oxide content. Finally, ultrasonic degassing process was contrasted to a conventional rotary degassing technique, comparing their efficiency.This work has been done within the AL-STRUC project supported by the ELKARTEK program of the Basque Government under Grant KK-2017/00020

Effect of Heat Treatment on the Microstructure and Hardness of Ni-Based Alloy 718 in a Variable Thickness Geometry Deposited by Powder Fed Directed Energy Deposition

Feature addition to existing parts is a trending application for Directed Energy Deposition (DED) and can be used to add complex geometry features to basic forged geometries with the aim to reduce and simplify the number of processing steps as machining and assembling. However, the mechanical properties of as-deposited Inconel 718 fabricated by Powder-fed Directed Energy Deposition (Powder-fed DED) are far lower than the relevant specifications, making it necessary to apply different heat treatment with the purpose of improving deposited material performance. In addition, the effects of heat treatments in both variable thickness deposited geometry and forge substrate have not been studied. In this study, the effect of heat treatment within the Aerospace Materials Specifications (AMS) for cast and wrought Inconel 718 on the microstructure and hardness of both the Ni-Based Alloy 718 deposited geometry and substrate are analyzed in different parts of the geometry. The microstructure of all samples (as-deposited and heat-treated) is analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), confirming the formation of aluminum oxides and titanium nitrides and carbonitrides in the deposited structure.This research was funded by the vice-counsel of technology, innovation and competitiveness of the Basque Government (Eusko Jaurlaritza) under the ELKARTEK Program, QUALYFAM and EDISON projects, grant number KK-2020/00042 and KK-2022/00070, respectively

Effects of Mn addittion, cooling rate and holding temperature on the modification and purification of iron-rich compounds in AlSi10MnMg(Fe) alloy

The use of secondary aluminum alloys in industry is still limited by the high Fe contents in recycled alloys. In general, the Fe-rich intermetallic compounds deteriorate the performance of secondary Al–Si alloys, specially the β-Fe phase. To mitigate the detrimental effects of iron, the influence of diferent cooling rates and holding temperatures on the modification and purification of iron-rich compounds in commercial AlSi10MnMg alloy with 1.1 wt % Fe was studied. According to the results obtained by CALPHAD calculations, the alloy was modified by adding a 0.7 wt%, 1.2 wt%. and 2.0 wt% of Mn. The phase formation and morphology of iron-rich compounds was systematically studied and correlated by different microstructural characterization techniques. The experimental results showed that the detrimental β-Fe phase can be avoided by adding at least 1.2 wt % of Mn at the studied cooling rates. Finally, the effect of different holding temperatures in the sedimentation of Fe-rich compounds also was studied. Hence, the gravitational sedimentation experiments at different holding times and temperatures were conducted to validate the feasibility of the methodology in different processing conditions. The experimental results showed a high Fe removal efficiency up to 64% and 61%, after a holding time of 30 min at 600 °C and 670 °C, respectively. The addition of Mn improved the Fe removal efficiency but not gradually, as the best results were obtained in the alloy containing 1.2 wt % Mn.This work was supported by the Basque Government through the projects Elkartek CIRCU-AL: KK-2020/00016 and SosIAMet KK-2022/00110

Microestructura y comportamiento mecánico de la aleación Ti-6AI-4V procesada mediante fabricación aditiva de lecho de polvo Electron Beam Melting

171 p.En este trabajo se han estudiado la relación de algunas variables de fabricación para la aleación de titanio Ti-6Al-4V fabricado por el proceso de fabricación aditiva electron beam melting (EBM) y las características y propiedades intrínsecas del material resultante. La microestructura propia, obtenida por el proceso EBM, ha sido modificada mediante tratamientos térmicos basados en tres enfoques estudiando el efecto de varias velocidades de enfriamiento después de un tratamiento de recocido ß, el efecto de la temperaturas y tiempos de recocido en los espesores de las láminas ¿, y de parámetros de envejecimiento, tiempo y temperatura, tras un proceso de solubilización y temple al agua. Se han establecido una serie de correlaciones que relacionan el espesor de la lámina ¿ y las propiedades mecánicas del material. Se ha desarrollado una comprensión fundamental de los mecanismos de crecimiento de grietas por fatiga en relación con la microestructura direccional del EBM Ti-6Al-4V. Para ello se ha estudiado la propagación de grietas en dirección paralela y perpendicular a la dirección de fabricación del proceso EBM, para diferentes relaciones de tensión y etapas del proceso de crecimiento de grietas. Se ha investigado la interacción entre la microestructura direccional EBM y se ha comparado con la interacción de la microestructura recocida ß equiaxial obtenida tras un recocido por encima de la temperatura ß transus. Finalmente, también se ha realizado una comparación de microestructura, propiedades mecánicas y propiedades de fatiga entre el proceso EBM y el proceso LMD para el material Ti-6Al-4V.Tecnali

Development of an Innovative Low Pressure Die Casting Process for Aluminum Powertrain and Structural Components

An innovative Low Pressure Die Casting (LPDC) process has been developed for aluminum cast components based on the application of an extra pressure during the solidification process. The new process, named “Low Pressure Squeeze Casting” (LPSC) has been proved to be able to increase the solidification rate, refining the microstructure of the casting, and reducing its shrinkage porosity. Furthermore, the cycle time is also reduced, increasing the productivity of the process. Two demonstrators from the automotive and wind power industries have been produced to validate the process in a relevant industrial environment.European Commission´s FP7, 314582, EFEV

Novel Assessment Methodology for Laser Metal Deposition of New Metallic Alloys

Metal additive manufacturing technologies are gaining great interest. However, the existing metallic alloys are generally formulated for conventional manufacturing processes. Thus, it is necessary to adapt their chemical composition or develop new alloys for the manufacturing conditions of additive manufacturing processes. The main method for manufacturing metal powder is gas atomization, but it is very expensive with long manufacturing times. Therefore, it is necessary to develop alloy validation methods that simplify the development process of new alloys. This paper deals with a methodology based on thermodynamic heat transfer equations, simulation, and powderless tests. This novel methodology enabled the determination of the optimal conditions for the laser melting deposition process of the commercial AA7075 alloy with a reduced number of experimental tests with powder, reducing the difficulties inherent to powder processing. The developed process was divided into two stages. In the first stage, the heating of the substrate was studied. In the second stage, the depositions of single tracks were validated with the parameters extrapolated from the previous stage. Hence, it was possible to manufacture single tracks free of cracks with an adequate aspect ratio