Metal Powders For Additive Manufacturing Research Articles

Selective Laser Melting of Metal Powders in Additive Manufacturing

Selective Laser Melting of Metal Powders in Additive Manufacturing

Characterization of Gas Atomized Ti-6Al-4V Powders for Additive Manufacturing

In this paper, titanium powders from various sources were characterized to compare powder intergrity for additive manufacturing by selective laser melting process. Selective laser melting by powder-bed based Additive Manufacturing (AM) is an advanced manufacturing process that bonds successive layers of powder by laser melting to facilitate the creation of engineering components. This manufacturing approach facilitates the production of components with high geometrical complexity that would otherwise be impossible to create through conventional manufacturing processes. Although the use of powder in AM is quite common, powder production and optimization of powder properties to yield desired performance characteristics has posed a serious challenge to researchers. It is therefore critical that powder properties be studied and controlled to ensure reliability and repeatability of the components that are produced. Typically, the desired feature of high quality titanium metal powders for AM are a combination of high sphericity, density and flowability. Scanning electron microscopy, EDS, particle size distribution and powder rheology were extensively performed to investigate the properties of gas-atomized Ti-6Al-4V powders.

Standard method for microCT-based additive manufacturing quality control 4: Metal powder analysis

X-ray micro computed tomography (microCT) can be applied to analyse powder feedstock used in additive manufacturing. In this paper, we demonstrate a dedicated workflow for this analysis method, specifically for Ti6Al4V powder typically used in commercial powder bed fusion (PBF) additive manufacturing (AM) systems. The methodology presented includes sample size requirements, scan conditions and settings, reconstruction and image analysis procedures. We envisage this method will support standardization in powder analysis in the additive manufacturing community. This is aimed at ultimately improving the quality of additively manufactured parts, through the identification of impurities and defects in powders.•MicroCT analysis of metal powders for additive manufacturing•Method describes a standard workflow simplifying usage of the technique•Sample requirements and image analysis workflow is described

Development of Metal Powders for Additive Manufacturing

Development of Metal Powders for Additive Manufacturing

Calculation of laser absorption by metal powders in additive manufacturing.

We have calculated the absorption of laser light by a powder of metal spheres, typical of the powder employed in laser powder-bed fusion additive manufacturing. Using ray-trace simulations, we show that the absorption is significantly larger than its value for normal incidence on a flat surface, due to multiple scattering. We investigate the dependence of absorption on powder content (material, size distribution, and geometry) and on beam size.

Metal Powder for Additive Manufacturing

Metal additive manufacturing (AM) processes are poised to transform the metal manufacturing industry, particularly in those areas where conventional manufacturing reaches its limitations in terms of both design freedom and manufacturing capabilities. Many metal AM systems are available today, including the powder-bed, powder-fed, and wire-fed processes based on laser, electron beam or plasma melting. At the same time, the variety of metal powder materials suitable for AM continues to expand. Currently there are 29 common metal powder materials available for AM, including stainless steels, aluminum, nickel, cobalt-chrome, and titanium alloys. The articles selected for this focus topic of JOM under Metal Powder for Additive Manufacturing are largely focused on metal powder for powder-bed fusion AM processes. The importance of metal powder characteristics in the powder-bed fusion AM processes has become increasingly recognized. How the powder flows and packs, can have a significant impact on powder bed formation, and hence the development of melt pools and microscopic homogeneity. Excessive variations in powder characteristics can lead to nonuniform layering, inconsistent bulk density, increased defects, undesired mechanical properties, and poor surface finish. As a result, it is essential to be able to identify the various powder characteristics that can ensure consistent and reliable performance, particularly when a lower cost, less spherical powder is intended for AM. In the first article, Slotwinski and Garboczi discuss the metrology needs for metal AM powders. The authors provide an informative overview of the current technical challenges and needs in characterizing metal powders for AM, processes based on laser, electron beam or plasma melting including recent efforts to standardize characterization methods in the ASTM International (ASTM) and the International Organization for Standardization (ISO), such as the recently released ASTM F3049, Standard Guide for Characterizing Properties of Metal Powders Used for Additive Manufacturing Processes. In the second article in this compilation, Clayton et al. show the necessity of appropriate metal powder characterization for AM through four case studies, and the inability of conventional characterization techniques to detect the subtle differences. These four case studies deal with (I) quantifying batch-to-batch variation in feedstocks, (II) the influence of different suppliers and manufacturing methods, (III) the effect of additives on feedstock properties, and (IV) process-relevant differences between fresh and used feedstocks. These are all important issues in metal AM. The third article by Strondl and co-workers is concerned with the characterization and control of powder properties for AM. The authors discuss the combined use of powder rheology and dynamic image analysis to characterize metal powders for AM. This study adds another useful case study to metal powder characterization for AM. In the fourth article in this sequence, Tang et al. report on the effect of powder reuse times on the AM of Ti-6Al-4V using an Arcam EBM A2 system (Arcam AB, Molndal, Sweden). Parts manufacturers are always both qualityand cost-conscious. In metal AM processes, the powder reuse times directly affect the affordability of the additively manufactured parts. Hence, it is necessary to identify the effect of powder reuse times on the AM process and the mechanical properties of the alloy thus fabricated. The powder composition, particle size distribution, apparent density, tap density, flowability, and particle morphology were studied as a function of powder reuse times and compared with respective properties of the virgin Arcam Ti-6Al-4V powder. Detailed tensile mechanical property data were produced from samples fabricated using Ti-6Al-4V powder that had been reused 16 times. The samples Ma Qian is the guest editor for the Powder Materials Committee the TMS Materials Processing and Manufacturing Division (MPMD), and coordinator of the topic Metal Powder for Additive Manufacturing (3D Printing) in this issue. JOM, Vol. 67, No. 3, 2015

Optimising metal powders for additive manufacturing

Powder rheometry can be used to ensure that metal powders for additive manufacturing deliver the performance and consistency required in demanding applications. Jamie Clayton, Operations Director of Freeman Technology Ltd and Rob Deffley, R&D Manager of LPW Technology Ltd, explain.

Cold forging of MMCs of aluminium alloy matrix: Wagener, H.W. and Wolf, J. J. Mater. Process. Technol. (Feb. 1993) 37 (1–4), 253–265

Due to the high efficiency and low cost, gas atomization (GA) has been widely applied to produce metal powders. In this paper, the GA process is first modeled by combining the volume of fluid (VOF) model with dynamic adaptive mesh and the discrete phase model (DPM) to simulate the formation of the powders and the evolution of the defects. Simulation results show that the Kelvin-Helmholtz instability in the primary atomization and the membranous droplet breakup and closure in secondary atomization can form the hollow powder. While the presence of the satellite powder is caused by the collisions between the large and small droplets with different velocities. Moreover, the irregular powder is produced when the drag force is not enough to separate the droplets but deforms them. The estimated morphology and size distribution of the particles have a good agreement with the experimental ones. Finally, the possible measures to reduce the defects of the powders have been put forward based on the revealed mechanism of defect evolution. This work provides a deep simulation insight into the GA process, towards producing high-quality metal powders for additive manufacturing on a large scale.