Nicholas J.E. Adkins

University of Birmingham

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Moataz M. Attallah

University of Birmingham

P. Tsakiropoulos

University of Sheffield

Khamis Essa

University of Birmingham

Hany Hassanin

Canterbury Christ Church University

Chunlei Qiu

Beihang University

Andrew M. Mullis

University of Leeds

Martin Heilmaier

Karlsruhe Institute of Technology

Marco Mulser

Attocube Systems (Germany)

Robert F. Cochrane

University of Leeds

C. Seemüller

Karlsruhe Institute of Technology

Cooperative Institutions

University of Birmingham

Leiden University

Universitat Politècnica de València

Institute of Metallurgy

Centre National de la Recherche Scientifique

Swansea University

Karlsruhe Institute of Technology

University of Cambridge

University of Leeds

Consejo Superior de Investigaciones Científicas

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Design of powder metallurgy aluminium alloys for applications at elevated temperatures Part 2 Tensile properties of extruded and Conformed gas atomised powders

Materials Science and Technology (1991)

Nicholas J.E. Adkins P. Tsakiropoulos

AbstractAbstractThe effects of aging treatments on the tensile properties and microstructure of Al–Cr–Zr–Mn powder metallurgy aluminium alloys prepared from high pressure gas atomised powders were investigated. The alloy compositions were designed to give powders with or without Al13Cr2 intermetallics in the <45 μm size fraction. The Al–5·2Cr–1·4Zr–1·3Mn alloy is typical of the former (concentrated alloy) and the Al–3·3Cr–0·7Zr–0·7Mn alloy of the latter (dilute alloy). The alloys were prepared using a canning/degassing/extrusion sequence or the Conform consolidation process. Measurements of micro hardness and electron microscopy were used to correlate the microstructure with the tensile properties. The extruded powders of both alloys exhibited better properties than those of the Conformed powders. A large contribution to the strength of the extruded materials is made by their stabilised fine grain size. The dilute alloys had consistently better ductility. Neither alloy retained its strength after prolonged aging at 400°C, but the results indicate that a service temperature of 300°C may be possible.MST/1247b

Powder Metallurgy

Ductility (Earth science)

6063 aluminium alloy

10.1179/mst.1991.7.5.419

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Citations (19)

Comparison of LPBF processing of AlSi40 alloy using blended and pre-alloyed powder

Additive Manufacturing Letters (2022)

Rebecca Garrard Donal Lynch Luke N. Carter Nicholas J.E. Adkins Rodolfe Gie

Elemental powders or pre-alloyed powders can be blended to form a powder stock with new compositions. In-situ alloying of blended powder mixtures during LPBF processing speeds up the alloy development process as it allows composition adjustment. Pre-alloyed powder is typically used in industrial settings to ensure consistency of the built material, whereas blended powders are used to experiment with new alloy compositions. In this research, we compare a range of binary alloy compositions built from blended elemental powder and pre-alloyed powder to evaluate how the feedstock powder affects the built material. The alloy is a lightweight alloy with a low coefficient of thermal expansion, comprised of Al and Si. The following compositions were formed by mixing pure Al and Si powder: AlSi38, AlSi40 and AlSi42, and pre-alloyed AlSi40 powder was also used. Parametric studies were performed for both the blended and pre-alloyed powders. It was found that the optimum process parameters for the blended and pre-alloyed powder were different. The line energy for pre-alloyed powder was selected to be 0.150 J/mm (300 W, and 2000 mm/s) which yielded a density of 99.5% of the theoretical density. The optimal density for the blended powders was 99.07-99.16% which was also achieved with 0.150 J/mm (375 W, 2500 mm/s). The alloys are brittle, with Young's modulus 86-99 GPa. Coefficient of thermal expansion (CTE) reduced with increasing Si content, material built from pre-alloyed powder had 5% higher CTE than material built from blended powder.

Brittleness

10.1016/j.addlet.2022.100038

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Citations (5)

Influence of processing conditions on strut structure and compressive properties of cellular lattice structures fabricated by selective laser melting

Materials Science and Engineering A (2015)

Chunlei Qiu Sheng Yue Nicholas J.E. Adkins Robin Ward Hany Hassanin

AlSi10Mg cellular lattice structures have been fabricated by selective laser melting (SLM) using a range of laser scanning speeds and powers. The as-fabricated strut size, morphology and internal porosity were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray microtomography (micro-CT) and correlated to the compressive properties of the structure. Strut diameter was found to increase monotonically with laser power while the porosity was largest at intermediate powers. Laser scanning speed was found to thicken the struts only at slow rates while the porosity was largest at intermediate speeds. High speed imaging showed the melt pool to be larger at high laser powers. Further the melt pool shape was found to vary cyclically over time, steadily growing before becoming increasingly instable and irregularly shaped before abruptly falling in size due to splashing of molten materials and the process repeating. Upon compressive loading, lattice deformation was homogeneous prior to the peak stress before falling sharply due to the creation of a (one strut wide) shear band at around 45° to the compression axis. The specific yield strength expressed as the yield stress/(yield stress of the aluminium × relative density) is not independent of processing conditions, suggesting that further improvements in properties can be achieved by process optimisation. Lattice struts failed near nodes by a mixture of ductile and brittle fracture.

Selective Laser Melting

Brittleness

Laser Scanning

10.1016/j.msea.2015.01.031

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Citations (331)

Influence of the processing technique on the properties of Nb-Si intermetallic composites for high temperature applications processed by MIM and HIP

Marco Mulser T. Hartwig C. Seemüller Martin Heilmaier Nicholas J.E. Adkins

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A technique for evaluating aluminium alloys for high pressure gas atomization

Materials Science and Engineering (1988)

Nicholas J.E. Adkins P.S. Goodwin P. Tsakiropoulos

Gas pressure

10.1016/0025-5416(88)90138-3

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Citations (5)

Suspended droplet alloying: A new method for combinatorial alloy synthesis; nitinol-based alloys as an example

Journal of Alloys and Compounds (2018)

Sheng Li Nicholas J.E. Adkins Stephen McCain Moataz M. Attallah

Combinatorial synthesis

10.1016/j.jallcom.2018.07.260

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Citations (8)

Production of Ultrafine Aluminium Powder by High Pressure Gas Atomization

Powder Metallurgy (1986)

R. A. Ricks Nicholas J.E. Adkins T.W. Clyne

AbstractThe paper is concerned with the production of ultrafine aluminium alloy powder by the relatively novel route of gas atomization at high pressures (4–8 MPa). It is shown that such a process is capable of the bulk production of rapidly solidified alloy powder having a median diameter below 20 μm. Some process variables are discussed and preliminary results obtained from the operation of a high pressure gas atomizer at the University of Surrey are presented. In addition, some results concerning the consolidation behaviour of such rapidly solidified powder are discussed. PM/0371

Aluminium powder

Powder Metallurgy

Consolidation

Gas pressure

10.1179/pom.1986.29.1.27

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Citations (8)

Novel Hybrid Manufacturing Process of CM247LC and Multi-Material Blisks

Micromachines (2020)

Xiqian Wang Luke N. Carter Nicholas J.E. Adkins Khamis Essa Moataz M. Attallah

The study on CM247LC used the traditional approach for Near-Netshape Hot Isostatic Pressing (NNSHIP) with sacrificial low carbon steel tooling, which was built using Selective Laser Melting (SLM), to produce a shaped CM247LC blisk. The assessment of the microstructure focused on both the exterior components in order to determine the depth of the Fe-diffusion layer and on the interior microstructure. Samples were extracted from the Hot Isostatic Pressed (HIPped) components for tensile testing at both room and elevated temperatures. The components were scanned to assess the geometrical shrinkages due to Hot Isostatic Pressing (HIPping). An oversized blisk was also produced based on the measurements as a demonstrator component. In addition, a further study was carried out on a novel idea that used a solid IN718 disk in the centre of the blisk to create a multi-material component.

Hot isostatic pressing

Component (thermodynamics)

Carbon fibers

10.3390/mi11050492

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Citations (13)

CLOSE-COUPLED GAS ATOMIZATION: HIGH-FRAME-RATE ANALYSIS OF SPRAY-CONE GEOMETRY

International journal of powder metallurgy (2008)

Andrew M. Mullis Nicholas J.E. Adkins Zabeada Aslam Ian N. McCarthy Robert F. Cochrane

The geometry of the spray cone during atomization of Ni31.5Al68.5 in a close-coupled gas atomizer operating with a generic die and nozzle design has been studied utilizing high speed digital video techniques. Details of the region extending 5 cm from the spray nozzle at frame rates of up to 18,000 frames/s were recorded. The material was sprayed at a temperature ∼1830 K (corresponding to a superheat ~200 K), wherein sufficient thermal radiation was emitted for images to be recorded without any additional lighting. In order to quantitatively analyze the large number of still frames that result (up to 65,536), image processing routines capable of automating this process have been developed and used to measure the optical brightness and the position of the optical intensity maximum of the material passing though a narrow window at a fixed distance from the nozzle tip. The results of this analysis show that the spray cone consists of a jet that precesses around the center axis of the atomizer in a regular manner at a frequency ~360 Hz. In order to understand the origin of this motion further experiments were conducted with a laboratory-scale analogue atomizer which atomizes a water jet. It was found that the frequency of precession is essentially independent of the atomizing gas pressure, but does depend upon the geometry of both the die and nozzle.

Precession

Ligand cone angle

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Citations (11)

Spray drying of TiO2 nanoparticles into redispersible granules

Powder Technology (2010)

Bertrand Faure Jesper Sæderup Lindeløv Michael Wahlberg Nicholas J.E. Adkins Phil Jackson

Suspension

Sonication

Aqueous suspension

Microparticle

Particle (ecology)

10.1016/j.powtec.2010.05.033

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Citations (52)