Nicholas P Lavery

Swansea University | SWAN · Future Manufacturing Research Institute

A series of small iron specimens with minor additions of C, Si and Mn were manufactured via induction melting and characterised using a high throughput methodology. The aim was to analyse the high throughput approach itself, not the effects of minor additions to steel. Despite their small size, the trends in measured standard mechanical properties...

Additive manufacturing by selective laser melting (SLM) was used to investigate the effect of laser energy density on 316L stainless steel properties. Point distance and exposure time were varied and their impact on porosity, surface finish, microstructure, density and hardness, was evaluated. The surface roughness was primarily affected by point d...

The primary aim of this investigation was to understand the effect of temperature fluctuations on a number of various solder materials namely SAC105, SAC305, SAC405 and Sn–36Pb–2Ag. To achieve this objective, three different classic joint assemblies (a ball joint, a test specimen joint and finger lead joint) were modeled which provided the foundati...

This paper presents a cradle-to-grave comparative Life Cycle Assessment (LCA) of new gas atomized (GA) sponge nickel catalysts and evaluates their performance against the both cast and crush (CC) sponge nickel and platinum standards currently used in commercial alkaline fuel cells (AFC). The LCA takes into account the energy used and emissions thro...

An environmental comparison is made between two gamma titanium aluminide (γ-TiAl) alloys, Ti–46Al–8Nb and Ti–46Al–8Ta (at.%), and the standard nickel superalloy, INC713LC used for investment cast components in the low pressure (LP) turbine section of aero-engines. Over the complete lifetime, weight reduction by direct replacement could give signifi...

To accelerate the development of new steel products, efforts have been made to miniaturise the steel making process. Reducing sample size allows multiple compositions to be made quickly and inexpensively. The rapid alloy prototyping (RAP) technique described in this work involves casting and processing samples in the range 40g to 140g. One of the c...

This study aims to investigate the feasibility of using non-standard miniaturized tensile specimens (MTS) to characterize the formability features of interstitial-free (IF) steel, specifically DX57 steel. The motivation behind this research is to gain insight into the accuracy of predicted values for the steel's formability using the designed non-s...

This work has two main objectives. The primary objective is to determine the ductile fracture mechanism of Dual-phase 800 as-cast materials by researching the relationship between triaxiality and fracture strain. The secondary objective is to determine the capability of 40/80g rapid alloy prototyping (RAP) routine, including tolerance limits. To ac...

There has been much interest in tin selenide (SnSe) in the thermoelectric community since the discovery of the record zT in the material in 2014. Manufacturing techniques used to produce SnSe are largely energy-intensive (e.g., spark plasma sintering); however, recently, in previous work, SnSe has been shown to be produced via a low embodied energy...

Tin selenide (SnSe) has attracted much attention in the field of thermoelectrics since the discovery of the record figure of merit (zT) of 2.6 ± 0.3. While there have been many publications on p-type SnSe, to manufacture efficient SnSe thermoelectric generators, ann-type is also required. Publications on n-type SnSe, however, are limited. This pape...

This work aims to investigate feasibility of using non-standard miniaturized tensile specimens (MTS) to characterise total elongation and formability behaviour of dual phase steels: to establish the scaling rules for MTS to predict a range of mechanical properties of steels obtained through rapid alloy prototyping (RAP) in the laboratory. Accurate...

This work investigated the feasibility of using miniaturized non-standard tensile specimen to predict the post-necking behaviour of the materials manufactured via a rapid alloy prototyping (RAP) approach. Experimental work focused on the determination of the Lankford coefficients (r-value) of dual-phase 800 (DP800) steel and digital image correlati...

Physical Vapour Deposition (PVD) is being developed as a coating process for steel substrates and is undertaken in high vacuum conditions to minimise contaminants mixing with the zinc vapour. The low-pressure conditions in the vacuum chamber, equates to large Knudsen numbers for the flow, due to this, continuum CFD methods tend to become invalid. F...

Laser powder bed fusion (LPBF) components display higher porosity compared to parts made by conventional processes and these pores act as preferential initiation sites for pitting corrosion to occur. In stainless steels such as 316L, molybdenum is 3.5X more effective at enhancing the pitting resistance than chromium, without adding unwanted nitride...

In the current work an accelerated process of alloy development that inherently connects a range of different production scales is presented; from laboratory route (20g cast) to pilot line (50kg cast) to industrially processed material. Recently optimized 20g Rapid Alloy Prototyping (RAP) casts been successfully produced with the potential to suppo...

This work compares the mechanical and corrosion properties of 316 L steel manufactured by Laser Powder Bed Fusion (LPBF) and post treated by Hot Isostatic Pressing (HIP) to wrought 316 L. HIP is often used by default on LPBF components to reduce porosity and obtain the best mechanical properties, however, if the HIP temperatures are too high, there...

A small-scale, rapid alloy prototypingRapid Alloy Prototyping (RAP) route is presented for accelerated lab-scale development of an array of steelsIron and steel across many applications in which alloys can be tailored with individual or combined elements to a compositional precision down to 0.1%. At the level of 40 g, over twenty unique composition...

High Entropy Alloys are often associated with good corrosion resistance and high hardness properties. These are of interest in demanding and premium high-security applications where high hardness (>700HV) and high tensile strength (>1200 MPa) materials are required. In transport applications lightweight materials (<7 g/cc) are also desirable. These...

Thermoelectric materials can convert waste heat to electricity without moving parts. Extensive research into improving the efficiency of inorganic thermoelectric materials has allowed some materials such as bismuth tellurides to be commercialized. These materials, however, contain materials in low abundance on earth such as tellurium therefore thei...

This work aims to evaluate the use of miniaturized tensile specimen (MTS) to characterise the mechanical properties of alloys developed through rapid alloy prototyping (RAP), where high throughput tests are required on relatively small amounts of material. Tensile tests were conducted at a variety of strain rates and with increasingly smaller speci...

Electromagnetic brake (EMBr) technique is adopted to reduce the turbulence of molten alloy in the slab mould in the continuous casting process, especially under high casting speed. We introduce a state-of-the-art EMBr technique by reviewing the published literature. The main objective of this paper is to give a clear view of the EMBr technique in t...

According to a recent Hume-Rothery approach, the electron concentration, e/a, and the average radius can be used to identify the domain of stability of HEAs and to estimate the phases that may occur in the alloy. The present study investigates the influence of the electronic structure and the average radius on the hardness for a series of HEA alloy...

Additive manufacture (AM) has revolutionized the manufacturing industry by developing a method of manufacture that allows for rapid prototyping, increased design freedom, and flexible production. Despite this, additively manufactured components exhibit a greater susceptibility to corrode. The corrosion properties of additively manufactured 17-4PH s...

Lattice materials are characterised by their equivalent elastic moduli for analysing mechanical properties of the microstructures. The values of the elastic moduli under static forcing condition are primarily dependent on the geometric properties of the constituent unit cell and the mechanical properties of the intrinsic material. Under a static fo...

High Entropy Alloys (HEA) can be classified in three domains according to their e/a and r values, with e/a, the number of itinerant valence electrons and r the average radius for a 12 nearest atoms neighborhood. The phase composition, thermal stability and possible phase transformations of a series of HEA alloys, CoCrzFeNi-XY (with X and Y = Al, Cu...

Over many decades, the traditional route for material product developments, especially in the steel industry has been the laboratory VIM cast route at scale of 25 to 60kg, followed by through-processing of steel ingots involving hot rolling and cooling as well as further downstream processes to simulate finished cold annealed rolled and coated prod...

The toxicity, earth abundance and manufacturing costs of thermoelectric materials are three leading reasons why thermoelectric generators are not used in wide scale applications. This is the first paper to tackle all three of these problems simultaneously. A pseudo-3D printing technique is combined with Cu2-xS based inks to yield bulk samples capab...

The effects of cold and warm rotary swaging and subsequent post-process annealing on mechanical properties, residual stress, and structure development within WNiCo powder-based pseudo-alloy were predicted numerically and investigated experimentally. The swaging temperature of 900 °C imparted increase in the Young’s and shear moduli; the post-proces...

A Renishaw AM 400 was used to produce Laser Powder Bed fusion (LPBF) iron alloy Invar ® and 17-4PH components. Build parameters were systematically changed and the corrosion performance of the samples produced was investigated using a combination of scanning vibrating electrode technique (SVET) and advanced conventional electrochemical techniques....

Dear Colleagues, Since their emergence in 2004, so-called high-entropy alloys (HEAs), also known as multi-major component alloys, have attracted much scientific interest. HEAs have opened up a rich new metallurgical field to be explored. Some 15 years later, we now intend to provide an account of the state-of-the-art in this area. Therefore, for t...

Since the discovery of the record figure of merit (ZT) of 2.6 ± 0.3 in tin selenide (SnSe), the material has attracted much attention in the field of thermoelectrics. This paper reports a novel pseudo‐3D printing technique to fabricate bulk SnSe thermoelectric elements, allowing for the fabrication of standard configuration thermoelectric generator...

High entropy CrxAlFeCoNi alloys with x = 0, 0.5, 1.0 and 1.5 were synthesized using arc-melting and sintering preparation techniques. Three crystal structures (fcc, bcc and σ) were observed using XRD technique, while EDX measurements showed the presence of up to three chemically different phases (FeCr-rich phase with fcc structure, AlNi-rich phase...

Twist channel angular pressing (TCAP), the severe plastic deformation (SPD) technology developed recently to increase the efficiency of the imposed strain and its homogeneity within a single pass, is an effective process combining channel bending and twist extrusion in a single die. The presented study analyses the phenomena of substructure develop...

Tungsten is considered as one of the most promising materials for nuclear fusion reactor chamber applications. Wire + Arc Additive Manufacture has already demonstrated the ability to deposit defect-free large-scale tungsten structures, with considerable deposition rates. In this study, the microstructure of the as-deposited and heat-treated materia...

High Entropy Alloys (HEAs) are a fairly new class of alloys and, although there is still discussion concerning a definitive classification of what an HEA is, they are typically characterised as having five or more principal alloying elements each at a concentration of 5% or higher. HEAs are currently the focus of much research as they have the pote...

Laser powder bed fusion (L-PBF) is a complex process involving a range of multi-scale and multi-physical phenomena. There has been much research involved in creating numerical models of this process using both high and low fidelity modelling approaches where various approximations are made. Generally, to model single lines within the process to pre...

Tungsten is considered as one of the most promising materials for nuclear fusion reactor chamber applications. Wire + Arc Additive Manufacturing has already demonstrated the ability to deposit defect-free large-scale tungsten structures, with considerable deposition rates. In this study, the microstructure of the as-deposited and heat-treated mater...

A combinatorial approach was used to select points on the Cobalt Chrome Tungsten (Co-Cr-W) ternary phase diagram [1] for manufacturing using a Rapid Alloy Prototyping methodology which combines ball milling, powder compaction and induction melting, [2], [3]. Each composition selected was studied in three conditions as-cast, annealed for 4 hrs at 11...

The temperature and time dependent structure of molten NiP alloy of eutectic composition has been studied by neutron diffraction. Ni particles were found to exist in the melt at temperatures at least up to about 150 degrees above liquidus. The amount varies reversibly as temperature increases but decays slowly with time. Remarkably, particles still...

Since their early development, High-Entropy Alloys have fueled the investigation of exotic metal combinations. Here, we present a strategy for the rational design of a library for multi-component alloys based on six hcp-structured metals. Seven five- and six-component equimolar alloys based on Co, Gd, Y, Sc, Ti and Zr were prepared via induction me...

We investigate the effect of alloying with scandium on microstructure, high-temperature phase stability, electron transport, and mechanical properties of the Al2CoCrFeNi, Al0.5CoCrCuFeNi, and AlCoCrCu0.5FeNi high-entropy alloys. Out of the three model alloys, Al2CoCrFeNi adopts a disordered CsCl structure type. Both of the six-component alloys cont...

Laser Powder Bed Fusion (L-PBF) is a powder based subcategory of metal additive manufacturing. In L-PBF systems an inert gas flow is used to avoid oxidation of the metal alloy powder and components but is also used to remove unwanted by-products produced from the vaporisation of material. By-products produced during in L-PBF can cause attenuation o...

Previous work has highlighted the importance of the gas flow system in laser powder bed fusion (L-PBF) processes. Inhomogeneous gas flow experienced at the surface of the powder bed can cause variations in mechanical properties over a build platform, where insufficient removal of by-products which cause laser attenuation and redisposition of by-pro...

The exceptional performance of some High Entropy Alloys (HEAs) under extreme conditions holds out the possibility of new and exciting materials for engineers to exploit in future applications. In this work, instead of focusing solely on the effects of high temperature on HEAs, the effects of combined high temperature and high pressure were observed...

Residual stress is a major problem for most metal-based laser powder bed fusion (L-PBF) components. Residual stress can be reduced by appropriate build planning and post-process heat treatments; however, it is not always avoidable and can lead to build failures due to distortion and cracking. Accurate measurement of residual stress levels can be di...

This study reports the results of the addition of different reinforcing agents (i.e. nano-diamonds, SiC, Sc2O3, h-BN, c-BN and CN) on the sintering process of the B2-structured Al2CoCrFeNi High-Entropy Alloy. The best candidate for further thermal, electrical and mechanical characterization was chosen to be the alloy containing 2 wt% nano-diamonds....

A full-scale 3D numerical model using the discrete element method is used to investigate three different chute designs for the charging of a blast furnace. The three chutes differ in the proportion of the chute that is either smooth or contains rock boxes. The uniformity of the delivery of burden materials is assessed as the burden passes through a...

The emergence of bulk metallic glasses and their identification as versatile advanced engineering materials with attractive properties has led to a surge in research efforts to investigate processing methods, which can be used either to synthesise new BMG alloys or to shape BMG workpieces into final components with specific geometries. Among such t...

The microstructure and mechanical properties of 316L steel have been examined for parts built by a powder bed laser fusion process, which uses a laser to melt and build parts additively on a layer by layer basis. Relative density and porosity determined using various experimental techniques were correlated against laser energy density. Based on por...

The corrosion performance of a Zinc Magnesium Aluminium alloy was shown to improve through the addition of a quaternary element, Germanium. Improved corrosion resistance can be attributed to microstructural changes in the alloy due to Ge addition while in the molten state. The proportion of the most active MgZn2 phase which has been shown to initia...

This research aimed at revealing the reasons for the extra Co-Cr-W alloy wastage in the risers in sand casting. The alloy filling behaviour in both the original and modified moulds was investigated numerically. The alloy-air interface was captured by using Volume of Fraction method. For the original mould, an unfilled volume in the vicinity of the...

A transient finite difference thermal model based on the heat equations is developed, valid for spectrally selective surface coatings on any substrate material within a near-infrared (NIR) furnace. Spectral radiative heat transfer equivalent to a blackbody provides the heat source. Both radiative and natural convective cooling are accounted for. A...

High-entropy alloys (HEAs) are single-phase systems prepared from equimolar or near-equimolar concentrations of at least five principal elements. The combination of high mixing entropy, severe lattice distortion, sluggish diffusion and cocktail effect favours the formation of simple phases—usually a bcc or fcc matrix with minor inclusions of ordere...

The pre-heating of natural gas supplied to both domestic and industrial use is required to counteract the Joule-Thomson effect due to pressure reduction. Most existing pre-heaters are in the form of water bath heaters, where both the burner and exchanger are immersed in a closed water tank. These systems usually have a low efficiency, and as a resu...

Despite its excellent elemental properties, lightweight nature and good alloying potential, scandium has received relatively little attention in the manufacturing community. The abundance of scandium in the Earth's crust is quite high. It is more abundant than silver, cobalt, lead and tin. But, because scandium is so well dispersed in the lithosphe...

Powder Bed Additive Manufacturing offers unique advantages in terms of manufacturing cost, lot size, and product complexity compared to traditional processes such as casting, where a minimum lot size is mandatory to achieve economic competitiveness. Many studies—both experimental and numerical—are dedicated to the analysis of how process parameters...

In order to increase the powder bed production rates, the laser power and diameter are increased enabling faster scanning, thicker powder layers and wider hatches. These parameters however interact in a very complex manner: For example increasing the laser power may lead to significant evaporation of the molten metal. Increasing the scan speed may...

In order to increase the powder bed production rates, the laser power and diameter are increased enabling faster scanning, thicker powder layers and wider hatches. These parameters however interact in a very complex manner: For example increasing the laser power may lead to significant evaporation of the molten metal. Increasing the scan speed may...

In soft-sphere discrete element models of granular flow, particles may interact in a variety of ways including interactions normal to points of contact and interactions tangential to points of contact such as sliding, rolling, bending and twisting. In the majority of models normal and sliding modes are used. Rolling friction is sometimes reported b...

Direct melting of metals is still the most widespread route for alloy mass production. However, the difference in Tm and relative affinity of metals often causes phase segregation and formation of several melts from the starting one. These issues can be limited with a careful design of the alloy, based on simple thermodynamic approximations and ΔHf...

In the work presented a 3D explicit transient finite difference solution has been developed to predict the thermal distribution and evolution during the build of a single layer of 316L steel powder. The aim of the model is to capture the general overall thermal distribution within a build which could potentially be used in a multiple-layer predicti...

Previous work has demonstrated that the flow of argon gas within a powder bed system can have a significant impact on the porosity and the strength of as-built parts, [1]. Argon is used as the inert environment of choice within powder bed systems, often in conjunction with prior chamber evacuation, to impede the formation of oxides which would hind...

High throughput, rapid prototyping of alloys requires a quick way to determine the mechanical properties of alloy compositions. Due to the nature of this manufacturing method only small samples are fabricated. To test mechanical properties of small samples the disk punch indenter approach was developed [1]. The disc-shaped specimens used in the dis...

A transient finite difference thermal model is formulated, valid for spectrally selective surface coatings on any substrate material within an ultra-fast near infrared (NIR) furnace and based on the heat equations. The irradiation from the NIR emitters provides the heat source and the model accounts for both radiative and convective cooling. A nove...

This paper assesses the use of computational fluid dynamics (CFD) to model the ventilation of a working marine vessel, its performance in extreme climates, and potential improvements to the ventilation system which could lead to increased efficiencies of the engine and generator set. Comparisons between data gathered on the marine vessel and the c...

The primary aim of this investigation was to understand the effect of temperature fluctuations on a number of various solder materials namely SAC105, SAC305, SAC405 and Sn-36Pb-2Ag. To achieve this objective, three different classic joint assemblies (a ball joint, a test specimen joint and finger lead joint) were modeled which provided the foundati...