Browsing by Author "Parker, Benjamin Stuart"

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    Blending of powders for in-Situ Alloying of Ti-6Al-4V laser powder bed fusion
    (Stellenbosch : Stellenbosch University, 2021-03) Parker, Benjamin Stuart; Blaine, Deborah; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Novel powder blending techniques for Ti-6Al-4V powder mixtures, using master-alloy (MA) and blended elemental (BE) powders as opposed to the industry standard of pre-alloyed (PA) Ti-6Al-4V powder,have been developed for laser powder bed fusion(LPBF), in particular direct metal laser sintering ®(DMLS®).The quality of a LPBF component is a result of both the metal powder characteristics and the LPBF process parameters. This study is limited to the metal powder characterisation of such blends, focussing on typical powder characterisation metrics of morphology, particle size distribution(PSD), flowability, apparent and skeletal density, and the angle of repose(AoR). A relatively novel metric of spreadability is a key focus in this study as it directly represents the mechanics of the LPBF recoating process. A spreadability test rig was commissioned in this work and obtained spreadability metrics of percent coverage and spread density.Moisture accumulation on stored metal powders has an adverse effect on flowability and spreadability of metal powders and was shown to significantly improve through air drying.It was found that MA or BE powder blends have spreadability characteristics similar to PATi-6Al-4V,with the standard metrics of particle morphology,PSD, flowability, and AoR having the most significant correlation to spreadability.This indicates that powders that: are more spherical, have a narrow PSD span, are highly flowable, and have a low AoR, have a better spreadability.