Author
Junfa Mei
Other affiliations: Brunel University London, Monash University, Imperial College London
Bio: Junfa Mei is an academic researcher from University of Birmingham. The author has contributed to research in topics: Microstructure & Laser. The author has an hindex of 19, co-authored 36 publications receiving 1541 citations. Previous affiliations of Junfa Mei include Brunel University London & Monash University.
Papers
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TL;DR: In this article, the effects of processing conditions, such as laser power, scan speed, powder feed rate, etc. on the microstructure of the build have been assessed and it has been found that Ti-6Al-4V is very susceptible to the formation of columnar grains during laser deposition.
372 citations
TL;DR: In this article, a finite element model has been established and used to predict the temperature history of direct laser fabricated (DLFed) Ti-6Al-4V thin wall samples, and the effects of laser power and the effect of location within a sample on its temperature history have been modeled and compared with temperatures measured during DLF using thermocouples.
Abstract: A finite element model has been established and used to predict the temperature history of direct laser fabricated (DLFed) Ti–6Al–4V thin wall samples. The effects of laser power and the effect of location within a sample on its temperature history have been modelled and compared with temperatures measured during DLF using thermocouples. The thermal history of the material has been correlated with the observed differences in the microstructures obtained at different locations in a given sample or for a given location in samples obtained at different laser powers.
132 citations
TL;DR: In this article, the authors found that the as-fabricated density of parts manufactured from Hastelloy-X by SLM could be increased from 77 to 99% by decreasing the laser scan speed, and that the degree of cracking can be reduced by decreasing minor alloying additions such as Mn and Si.
119 citations
15 Feb 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors used optical microscopy, scanning electron and transmission electron microscopy to characterise the microstructure of these samples and measured the room temperature tensile properties.
Abstract: Composites of Ti–6Al–4V containing different volume fractions of TiC were manufactured using direct laser fabrication. Ti–6Al–4V wire and TiC powder were fed into the laser with the rate of powder feed being changed so that samples containing different volume fractions of TiC could be manufactured. Optical microscopy, scanning electron and transmission electron microscopy were used to characterise the microstructure of these samples. The room temperature tensile properties were measured also on some selected compositions together with their Young's moduli. In addition the change in wear resistance was studied as a function of TiC volume fraction using a standard wear test. These observations are discussed in terms of the advantages and difficulties of using simultaneous wire and powder feed systems and in terms of the value of this approach in obtaining data over a wide range of compositions for such a composite.
113 citations
91 citations
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TL;DR: A review of the emerging research on additive manufacturing of metallic materials is provided in this article, which provides a comprehensive overview of the physical processes and the underlying science of metallurgical structure and properties of the deposited parts.
4,192 citations
TL;DR: Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser as discussed by the authors, which is based on a novel materials incremental manufacturing philosophy.
Abstract: Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...
2,402 citations
Book•
12 Mar 2014
TL;DR: In this paper, the 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).
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).
1,539 citations
TL;DR: Additive manufacturing (AM) technology has been researched and developed for more than 20 years as mentioned in this paper, and significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields.
Abstract: Additive manufacturing (AM) technology has been researched and developed for more than 20 years. Rather than removing materials, AM processes make three-dimensional parts directly from CAD models by adding materials layer by layer, offering the beneficial ability to build parts with geometric and material complexities that could not be produced by subtractive manufacturing processes. Through intensive research over the past two decades, significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields. This paper reviews the main processes, materials and applications of the current AM technology and presents future research needs for this technology.
1,502 citations
TL;DR: In this paper, the recent progress on Ti6Al4V fabricated by three mostly developed additive manufacturing techniques-directed energy deposition (DED), selective laser melting (SLM) and electron beam melting (EBM)-is thoroughly investigated and compared.
1,248 citations