HM Davies

• BEng 1ST CLASS HONOURS- MATERIALS ENGINEERING
• Professor (Associate) at Swansea University

The ambient temperature fatigue performance of the near alpha titanium alloy IMI834 was evaluated using laboratory specimens manufactured from two material sources: rolled bar stock and an isothermally forged compressor disc. The effect of dwell periods imposed at peak stress and R value were assessed. Significant differences were defined between t...

Evidence for sub-surface fatigue crack initiation is often reported for near alpha titanium alloys such as the coarse grained IMI685 and the fine duplex structured IMI834. In such materials with a typical as received hydrogen concentration of 40–60 ppm the initiation site is invariably characterized by quasi-cleavage facetting. Similar facetting is...

Iterative strain-recrystallization cycles have been applied to alpha-brass in order to enhance ductility while maintaining tensile strength. Five iterations of 25 pct uniaxial strain followed by a 300 second anneal at 665 °C were used to achieve the desired properties. This article concentrates on assessment of the effect of the processing on micro...

An EBSD-based methodology for assessment of grain boundary planes, in particular sigma3 boundaries in face-centred cubic materials, has recently been devised. The method is based on trace analysis in a single, two-dimensional section rather than the more arduous three-dimensional method. The paper reports a data set of grain boundary planes in alph...

This study investigated the fatigue performance of two forged variations of α + β titanium alloys, namely Ti-6Al-4V (Ti-6-4) and Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6) joined via the powder interlayer bonding (PIB) process. Both alloys were bonded at relevant temperatures in the specific alloy’s α + β region. Modifications to the microstructure during the...

Powder interlayer bonding (PIB) is a novel joining technique, which has been developed to facilitate high-integrity repairs of aerospace components, manufactured from commonly used titanium alloys. The PIB technique utilises an interlayer between complex geometric components which are mated under pressure and a highly localised heating source. In t...

Powder interlayer bonding (PIB) is a novel joining technique. The technique has been developed to facilitate high integrity repairs of aerospace components, manufactured from titanium alloys commonly employed in the aerospace industry. The PIB technique utilises an interlayer between the two faying surfaces. In this study heating was supplied via i...

Powder interlayer bonding (PIB) is a novel joining technique. The technique has been developed to facilitate high integrity repairs of aerospace components, manufactured from titanium alloys commonly employed in the aerospace industry. The PIB technique utilises an interlayer between the two faying surfaces. In this study heating was supplied via i...

This study introduces powder interlayer bonding (PIB) as a novel joining technique, for the high integrity repair of components, fashioned from two titanium alloys commonly employed in the aerospace industry. The PIB technique in this study utilised a metallic powder interlayer between the two faying surfaces. Heating was provided via induction to...

Microscopic Analyses of 316 L Stainless Steel Powder from Additive Layer Manufacturing Process - Volume 23 Issue S1 - H M Davies, S Mehmood, A Khaliq, S A Ranjha

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...

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...

Hydrogen induced cold cracking (HICC) and hydrogen embrittlement (HE) are influenced by the microstructural evolution, residual plastic strain (i.e. local misorientation), recrystallization of grains and the resultant grain boundary characteristic distribution (GBCD) brought about by welding processes. HICC and HE are known to cause failures in aer...

Brass samples were controllably tarnished using the thioacetamide accelerated corrosion (ISO 4538:1995) and synthetic sweat (ISO 3160–2:2003) methods. Spectrophotometry, energy dispersive X-ray spectroscopy (EDX) and electrochemical impedance spectroscopy (EIS) were performed on samples tarnished for set exposure times over seven days. Synthetic sw...

This paper presents an approach of how warpage (i.e. part deflection) and injection pressure of an intricate geometry could be minimised by selecting an optimal thermoplastic material and injection gate location (through which the molten plastic flows into the cavity). The numerical analyses for mould filling considered four gate locations along wi...

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...

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...

The connectivity between the boundaries is very important because the defect character of triple junctions is expected to have a significant influence on the bulk properties of materials, particularly mechanical behaviour. The investigation of triple junction investigations presented here indicates that a restricted Coincidence Site Lattice (CSL) m...

The present paper reports a comparative analysis of sigma 3 (in the coincidence site lattice notation) grain boundary types, in two grain boundary engineered brass specimens, by use of electron backscatter diffraction (EBSD) data coupled to the measurement of boundary traces in a single section. Although most of the data were analysed using the new...

This paper reports a study of the relationship between purpose-designed, iterative multi-stage thermomechanical treatments, grain boundary crystallography and subsequent ductility in alpha-brass. Grain boundary crystallographies were analysed not only in terms of proportions of coincidence site lattice (CSL) types but also, crucially, as proximity...

This review describes the theoretical basis, experimental considerations, data analysis and applications of studies of grain misorientations in cubic materials. Recently, there have been considerable advances in experimental techniques, allowing huge sample populations of misorientations to be collected. To handle such amounts of data, and to balan...

The present paper reports new experimental work to evaluate two aspects of thermomechanical treatment of α brass: the effect on the grain boundary population of strain annealing iterations rather than single stage treatments, and the accompanying effect on mechanical properties, particularly ductility. Whereas the first stage of a two stage strain–...