Rapidly Solidified Aluminium Research Articles

Optimization Strategy for Molecular Dynamics Simulations of Nanometric Cutting of Aluminium Alloy Using Molecular Modelling

Atoms constituting a metal define its molecular crystal structure (atomic system) and interact in molecular dynamics simulations of nanometric cutting of the metal. The removal of the material (metal) at nanoscale and generation of high quality surface with a nanometric finish is largely influenced by the mechanical and physical properties of the metal as it associates with the metal lattice (atomistic) structure. Improved studies of the molecular modelling (behaviour of molecules) as it creates mathematical models of molecular properties and behaviour of atomistic systems are required for condition prediction of a nanometric surface finish. In this study, atomic system of rapidly solidified aluminium (RSA) alloy, grade RSA 431, with the use of its alloying elemental compositions by weight percentage is designed and constructed with cell geometry and atom positions that are written into a data file using AtomsK program. In addition, atomic concentration influencing the structural properties of the alloying elements were calculated. Obtained microstructure depicts the spread of the elemental compositions and the data file is suitable for a code performing simulations on classical particles like the large-scale atomic/molecular massively parallel simulator (LAMMPS) software. Understanding the computer simulations (molecular dynamics) for analyzing the physical movements of atoms and molecules, and the peculiar characteristic properties of the composing alloying elements of the RSA 431 determine how much influence each of them (elements) has on the nanometric cutting surface. Hence, the nanometric surface finish of the RSA 431.

Reactive ion beam smoothing of rapidly solidified aluminum (RSA) 501 surfaces for potential visible and ultraviolet light applications

Optical elements made of aluminum with surface roughness in the sub-nanometer range are required for applications in the visible (VIS) and ultraviolet (UV) spectral range. Rapidly solidified aluminum (RSA) 501 is an interesting candidate to produce sufficiently smooth surfaces for these applications in an ultra-precision (UP) fly-cutting process. However, the polycrystalline grain structure and precipitates contained in the material limit the achievable surface roughness. In this research, a reactive ion beam finishing process of RSA 501 is investigated employing an electron cyclotron resonance (ECR)-driven ion source using CF4 and N2 gasses. Emphasis is placed on understanding the etching mechanisms that influence the topographic evolution to provide the basis for future production processes using the material for UV optics. Material composition characterization is applied to analyze the interaction between the reactive ion species and the RSA material. Surface modification transferring the native oxide top layer to an in situ forming and developing aluminum fluoride or -nitride etch front layer is found to prevent grain orientation-dependent etching. The effect of the ion incidence angle on the etch rates of precipitates and bulk material can be used to reduce the height of precipitates protruding from the surface after the UP-machining process. A surface roughness value of Sq = 0.9 nm ± 0.1 nm (areal root mean square height) is achieved in the micro-roughness range when etching at 40° and 80° angle of incidence using collimated ion beams with CF4 process gas.

Cast and Rapidly Solidified Aluminium Alloy with the Addition of Deep-sea Nodules

Reduced deep-sea nodules were tested as the alloying mixture for cast and rapidly solidified aluminium alloy. No separation of any metal was used in order to save the processing costs of the deep-sea nodules and to obtain “natural” ratios between the alloying elements. The resulting rapidly solidified alloys contained sharp-edged intermetallics, especially Al9Mn3Si phase, which was converted to rounded Al19Mn4 during thermal exposure. The hardness of the ribbons was almost stable during long-term annealing at 300 and 400 °C for 250 h. The alloy can be considered as highly thermally stable.

Effect of Tool Geometry and Turning Parameters on Cutting Force during Ultra-Precision Diamond Machining of Rapidly Solidified Aluminum (RSA) Alloy 6061

The most important goal of advanced diamond machining is to improve precision and product integrity. Cutting force could have a strong effect on diamond machining performance and hence, it can be used as an indicator for monitoring tool condition for achieving successful machining. Moreover, diamond machining process parameters such as cutting speed, depth of cut and feed rate may strongly influence the process outcomes in terms of surface roughness and tool failure. Diamond machining parameters have a significant role on the cutting force values, and machine-tool stability during ultra-high precision machining that makes use of a natural diamond cutting tool. The main objective of this research work is to investigate the effect of cutting speed, feed rate, depth of cut and nose radius on the cutting force generated during diamond turning of a rapidly solidified aluminum alloy grade called RSA 6061. The effect of nose radius and cutting parameters on cutting force during the ultra-high precision diamond turning process was monitored. The study shows that low speed, low depth of cut and an increase in feed rate at large nose radius consequently results in increase in the cutting force.

Acoustic Emission and Surface Roughness in Ultra-Precision Diamond Turning of RSA 6061 for Optics Applications

Machining Rapidly Solidified aluminium (RSA) 6061, a widely used optical material by Ultra-high precision diamond turning, has enabled high accuracy and surface integrity. However, improved quality and productivity require precision surface and machining process monitoring because the duo has a great influence on machine part performance. The study presented in this paper investigates the effects of cutting parameters (i.e., depth of cut, feed rate and cutting speed) on machining output variables (surface roughness and acoustic emission potentials) during ultra-high precision diamond turning of RSA 6061. With the aid of Box-Behnken design (BBD), a response surface methodology, and the analysis of variance (ANOVA), the correlation between cutting parameters and machining output variables were analyzed and modeled. The results showed that both surface roughness and acoustic emission potentials are greatly influenced by feed rate and cutting speed. For a better-quality surface roughness and low acoustic emission during ultra-high precision diamond turning of RSA 6061, high cutting speed and low feed rates are the right combinations and vice versa.

Ion beam planarization of optical aluminum surfaces

For fabrication of high-performance mirror devices, technical aluminum alloys Al6061 or Al905 are widely used. The surface error topography after manufacturing by single-point diamond turning is applicable in the infrared spectral range. For increasing demands on the optical surface quality in the shortwave visible and ultraviolet spectral range, further improvement of the surface roughness is required. Hence, a promising alternative process to attain the required surface quality is evaluated. Within the ion beam planarization technique, a photoresist layer is deposited by conventional spin coating or spray coating technologies exhibiting an ultrasmooth surface. When removing the resist by reactive ion beam etch (RIBE) processing using nitrogen process gas, the ultrasmooth surface topography of the resist is transferred into the substrate. We optimized the photoresist thermal pretreatment to realize roughness preservation and a steady-state material removal rate during RIBE machining. The optimum preparation steps are explored based on roughness evaluation, chemical modification, and etch resistance of the negative photoresist. Reactive ion beam etching-based planarization is conducted on single-point diamond turned RSA Al905 and RSA Al6061 samples made of rapidly solidified aluminum (RSA) in a two-step process. The optimum process and the roughness evaluation are explored by topographic analysis applying a combination of white light interferometry and atomic force microscopy measurements.

Cutting forces and acoustic emission in the diamond turning of rapidly-solidified aluminium

Cutting forces and acoustic emission in the diamond turning of rapidly-solidified aluminium

Molecular dynamics analysis of nanomachining of rapidly solidified aluminium

Rapidly solidified aluminium (RSA) is becoming more recognised as an alternative material to traditional aluminium alloys in the production of optical and structural components. This is due to its improved physical and mechanical properties and ultra-fine microstructure as a result of rapid solidification in the foundry process. The lack of past studies in the molecular dynamics simulation of RSA can be attributed to the lack of sufficient data on the microstructure and interatomic potential limitations. In this paper, an approximation of RSA was modelled to simulate the nanomachining process. The workpiece for the simulation was modelled as an aluminium lattice mixed with the appropriate fractions of the additional elements based on the chemical composition of RSA. The depth of cut was varied from 0.5 to 1.5 nm, and the cutting speed was varied from 5 to 15 m/s. The cutting process was found to be consistent with increase in depth of cut, producing a steady increase in energy, temperature and average cutting forces. Increase in cutting speed produced a slowing increase in energy and temperature while the average cutting forces showed an initial slowing increase followed by a rapid increase. The results showed that cutting speed had a more significant effect on the cutting process that will subsequently affect the desired surface finish. As the surface quality produced in ultra-high precision machining is in the nanoscale, the purpose of this research was to analyse the mechanisms occurring at the subsurface layers and establish a relation to the actual results produced. Experimental evaluations were carried out that agreed with the conclusions made with the MD simulation further proving the eligibility of the MD in nanomachining investigation.

Form Accuracy of Optical Mould Inserts Made from Rapidly Solidified Aluminium Alloys

Plastic optical components and lenses produced in mass quantities are usually manufactured using high-precision plastic injection technology. For that, high-precision plastic moulds with aluminium optical inserts made with extremely high dimension accuracy and high optical surface quality are used. Ultra-high precision single-point diamond turning have been successfully used in shaping optical mould inserts from various aluminium grades such as traditional 6061. However, extreme care should be taking when selecting machining parameters in order to produce optically valid surfaces before premature tool wear takes place especially when the machined optical materials has inadequate machining database. The current experimental study looks at the effect of cutting conditions on optical surfaces made from aluminium. The study embarks on helping establish some diamond machining database that helps engineers select the most favourable cutting parameters. The papers reports on the accuracy and surface finish quality received on an optical surface made on mould inserts from a newly developed aluminium alloy. Rapidly solidified aluminium (RSA) grades have been developed recently to address the various problems encountered when being cut by single-point diamond turning operation. The material is characterised by its extremely fine grained microstructure which helps extend the tool life and produce optical surfaces with nanometric surface finish. It is found the RSA grades can be successfully used to replace traditional optical aluminium grades when making optical surfaces. Surface finishes of as low as 10 nanometres and form accuracy of less than one micron can be achieved on RSA.

Diamond Machining of Rapidly Solidified Aluminium for Optical Mould Inserts

In this study, we conducted a series of machining tests on an ultra-high precision machining centre to investigate the wear mechanism of diamond inserts when rough turning a rapidly solidified aluminium grade, having increased contents of hard elements such as iron, nickel and molybdenum particles. This aluminium grade (RSA 905) produced by melt-spinning process could be used for making optical moulds for plastic lens injection as a re-placement of other traditionally used aluminium grades. The study yields some recommendations on the best combination of machining parameters that will result in maximum material removal rates with smallest possible damage to the tool edge. In this work, standard non-controlled waviness mono-crystalline diamond inserts are used to cut the aluminium alloy. The initial results of tool wear measurements indicate that diamond machining of this particular aluminium grades results in relatively intensive tool wear compared to other optical material. The study concludes that the tool wear is very noticeable on the diamond inserts operated at high feed rates.

Effect of Cr and Zr Dopes on Hydrogen Behaviour in Rapidly Solidified Aluminium Foils

Hydrogen (H) behaviour in materials was investigated in rapidly solidified (RS) foils of pure aluminium (Al), Al-0.4 Cr and Al-0.25 Zr alloys (at %) by means of thermal desorption spectroscopy (TDS). In addition, Al-0.25; 0.3 Zr alloys were examined with respect to microstructure and its instability during the thermal process using SEM and microhardness measurements. The effect of dopes and heating rate on H desorption was summarized. The lowest energy desorption is attributed with significant thermal desorption peak which temperature was found is correlated with sample composition.

On the Nature and Stability of Phases Present in a Rapidly Solidified Aluminium Alloy 7010 Containing Scandium

The influence of Sc on the nature and stability of phases present in rapidly solidified (RS) Al alloy 7010 (hereafter termed base alloy) produced by melt spinning were examined and compared with the phases present in the same alloys when produced by the conventional ingot metallurgical (IM) route. Transmission electron microscopy (TEM) revealed that the second phases present in the IM alloys have an HCP structure but with varying lattice parameters. On the other hand, the second phase particles present in the base alloy when produced by rapid solidification (RS) route always have a quasi-crystalline, icosahedral structure. In the rapidly solidified 7010 + Sc alloy, however, the icosahedral phase is located only at the grain boundary triple point junctions, and the grain interfaces are populated by the second phase particles having an HCP structure. An analysis of the chemistry of the second phase particles revealed that the icosahedral phase is stabilized by certain minimum concentrations of Zn + Mg/Zn + Mg + Cu. The reason for the absence of the icosahedral phase at the grain interfaces of the rapidly solidified 7010 + Sc alloy is the partitioning of relatively lower concentrations of the major alloying elements into the second phases formed at those sites. Micro-hardness measurements revealed higher hardness values for the RS 7010 + Sc alloy in both as-melt spun as well as artificially aged conditions. These results are correlated with the microstructures developed in these materials.

Rapidly solidified aluminium alloys by meltspinning

Abstract Rapid solidification of microcrystalline alloys makes it possible to create a new generation of aluminium alloys with superior strength, comparable to titanium. Whereas, the maximum strength level of conventional aluminium alloys does not exceed 550 MPa, titanium starts with a strength level from 750 MPa. Rapidly solidified aluminium (RSA) alloys produced by meltspinning is able to close the gap between aluminium and titanium. A wide range of applications like sporting goods, engine components, and aerospace parts can take advantage from the RSA alloys. In addition to strength, other properties such as thermal expansion, wear resistance and high temperature strength are also largely improved. RSP Technology in collaboration with Delft University is the first company that has successfully developed meltspun RSA on an industrial scale.

Processing, Structure and Mechanical Behavior of Rapidly Solidified Aluminum Alloys Containing Quasicrystalline Particles

Processing, Structure and Mechanical Behavior of Rapidly Solidified Aluminum Alloys Containing Quasicrystalline Particles

Large scale manufacturing of rapidly solidified aluminum alloys

A manufacturing process for rapidly solidified (RS) aluminum alloys, intended for aerospace structural applications, has been developed. Planar flow casting/ribbon comminution, powder degassing and compaction processes have been scaled up to produce RS aluminum alloy billets in large quantities. The billets have been converted to mill product forms utilizing extrusion, forging and rolling techniques. The alloys have superior mechanical properties such as a combination of good room temperature ductility and fracture toughness coupled with high modulii, and corrosion resistance. Recent work has shown that such properties can be retained in a variety of large product forms obtained from RS alloy billets. A wide range of aerospace applications, including airframe structures, gas turbine engines and missiles, have been demonstrated for AlFeVSi alloys. The RS AlLi alloys are ideally suitable for forging applications in airframe structures.

Surface Studies of Rapidly Solidified Aluminium Alloy Powder

Surface Studies of Rapidly Solidified Aluminium Alloy Powder

Production of Rapidly Solidified Aluminium Alloy Powders by Gas Atomisation and Their Applications

Light engineering alloys based on aluminium have been the subject of a great deal of attention in the field of rapid solidification processing. As a parallel activity, considerable research effort has been expended on the process of gas atomisation. Understanding of the process has improved, and the influence of processing parameters and nozzle design has been clarified. Results of recent research are reviewed in the present study. Influence of particle size on cooling rates is examined for various atomising gases, and a pilot plant gas atomiser for research into atomisation and for producing research quantity powders is described. Formation of particles and breakup of liquid in atomisation are discussed and related to the distribution of particle sizes in the powder. It is shown that for efficient powder production correct design of the atomising nozzle is of paramount importance. This is explained in terms of supersonic gas flow patterns in the atomising jet, and of the interaction between the gas jet and the liquid metal. The influence of metal temperature, nature and pressure of the atomising gas, production rate, and the level of oxygen in the gas is outlined and related to the particle formation mechanism. Alloy development is reviewed with particular reference to aluminium-transition metal systems for high temperature applications, as well as Al–Li based low density high strength alloy systems and metal matrix composites made from aluminium alloy powder matrix. PM/0511

急冷凝固法による結晶粒を微細化した純アルミニウムの強度に関する研究

Tensile tests and transmission electron microscope observations were performed on pure aluminum finely grained by rapid solidification. Experimental results obtained are as follows, 1) Aluminum specimens of the average minimum grain size 2.9μm are obtained by rapid solidification on single roll. The cooling rate of these specimens is estimated 3×106K/s.2) The yield stress and fracture elongation of finer grain specimens rapidly solidified are higher in tensile tests.3) There is Hall-Petch relation between grain size and yield stress. Comparing to recrystallized aluminum, the yield stress of rapidly solidified aluminum is higher. σ0 and ky of rapidly solidified aluminum in Hall-Petch relation are 14.6MPa and 2.1MPamm1/2, and those of the recrystallized are 10.4-8.5MPa and 1.8MPamm1/2.4) In a transmission electron microscope observation, tangling of dislocations, adhesion of dislocations to grain bounderies, secondery defects are observed. They are considered to be causes of higher yield stress of rapid solidified aluminum.

Structure/Property Relationships and Applications of Rapidly Solidified Aluminum Alloys

ABSTRACTDuring the last five years Pratt & Whitney Aircraft has developed rapid solidification powder metallurgy and consolidation techniques to produce advanced aluminum alloys. A centrifugal rotary atomization device with forced high velocity helium convective cooling has been developed to pilot-plant stage, to produce aluminum alloys of novel compositions for advanced gas turbine engine applications. Rapidly solidified aluminum alloys solidify as spherical droplets up to 100 μm diameter with cooling rates of 105 — 106 K/sec, and demonstrate new microstructural features which have been exploited to develop elevated temperature mechanical properties. Alloys have been developed for 400 — 500°F fan and compressor applications that have traditionally used titanium alloys, and this paper reviews the microstructural evolution of rapidly solidified structures during thermomechanical processing.