D.G. McCartney

Bio: D.G. McCartney is an academic researcher from University of Nottingham. The author has contributed to research in topics: Thermal spraying & Microstructure. The author has an hindex of 44, co-authored 159 publications receiving 6472 citations. Previous affiliations of D.G. McCartney include University of Liverpool & University of Oxford.

Grain refining of aluminium and its alloys using inoculants

Abstract: Grain structure is an important and readily observable feature in cast aluminium alloys. Three different types of grain morphology are possible, namely, columnar, twinned columnar, and equiaxed. Inoculants in the form of master alloys are used to promote the formation of a fully equiaxed grain structure and this is termed grain refinement. Initially, fundamental aspects of solidification are outlined in order that the principles of grain refining using master alloys can be understood. Techniques for the commercial production and testing of common Al–Ti-based master alloys are then discussed briefly. The exact mechanisms by which grain refinement occurs are not yet fully understood and experimental and theoretical studies on the problem are critically reviewed with particular emphasis on (a) the role of solute titanium, (b) the thermodynamics of Al–Ti-based alloy systems, and (c) the nature of heterogeneous nuclei. Finally, current and future trends in the use of grain refining alloys are summarised.

Bonding Mechanisms in Cold Spraying: The Contributions of Metallurgical and Mechanical Components

Abstract: The mechanism of bonding in cold spraying is still a matter of some debate. In this work, copper has been cold sprayed onto aluminium alloy substrates, the surfaces of which had been prepared in a variety of ways. The coating-substrate bonding was assessed via a novel intermetallic growth method along with adhesive pull-off testing, and related to the substrate preparation method. The bond strength has been rationalized in terms of a modified composite strength model, with two operative bonding mechanisms, namely (i) metallurgical bonding and (ii) mechanical interlocking of substrate material into the coating. In most cases, mechanical interlocking is able to account for a large proportion of the total bond strength, with metallurgical bonding only contributing significantly when the substrate had been polished and annealed prior to spraying. In addition, grit-blasting has been shown to significantly reduce the bond strength compared to other substrate preparation methods.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Laser Material Processing

Abstract: In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Consolidation/synthesis of materials by electric current activated/assisted sintering

Abstract: This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.