The Rapid Product Development Association of South Africa (RAPDASA) expressed the need for a national Additive Manufacturing Roadmap. Consequentially, the South African Department of Science and Technology commissioned the development of a South African Additive Manufacturing Technology Roadmap. This was intended to guide role-players in identifying business opportunities, addressing technology gaps, focusing development programmes, and informing investment decisions that would enable local companies and industry sectors to become global leaders in selected areas of additive manufacturing. The challenge remains now for South Africa to decide on an implementation approach that will maximize the impact in the shortest possible time. This article introduces the concept of a national Additive Manufacturing Centre of Competence (AMCoC) as a primary implementation vehicle for the roadmap. The support of the current leading players in additive manufacturing in South Africa for such a centre of competence is shared and their key roles are indicated. A summary of the investments that the leading players have already made in the focus areas of the AMCoC over the past two decades is given as confirmation of their commitment towards the advancement of the additive manufacturing technology. An exposition is given of how the AMCoC could indeed become the primary initiative for achieving the agreed national goals on additive manufacturing. The conclusion is that investment by public and private institutions in an AMCoC would be the next step towards ensuring South Africa's continued progress in the field. OPSOMMINGDie "Rapid Product Development Association of South Africa" (RAPDASA) het die behoefte aan 'n nasionale toevoegingsvervaardigingpadkaart uitgelig. Gevolglik het die Departement van Wetenskap en Tegnologie opdrag vir die ontwikkel van so 'n padkaart gegee. Hierdie was veronderstel om rolspelers te lei in die identifisering van besigheidsgeleenthede, die aanspreek van tegnologie tekortkominge, die fokus op ontwikkelingsprogramme en om beleggingsbesluite te beïnvloed wat plaaslike maatskappye en industrieë in staat sal stel om wêreldleiers op uitgekose areas van toevoegingsvervaardiging te word. Die uitdaging vir Suid-Afrika is nou op 'n toepassingsbenadering wat die maksimum impak in die kortste moontlike tyd sal verseker. Hierdie artikel stel die konsep van 'n nasionale Toevoegingsvervaardiging Sentrum van Bevoegdheid as 'n primêre toepassing van die padkaart voor. Die ondersteuning deur die hoof rolspelers in Suid-Afrika vir so 'n sentrum word gedeel en hulle onderskeie rolle is aangedui. Die rolspelers se toewyding word gestaaf aan die hand van hul beleggings in die fokus areas van die Sentrum oor die laaste twee dekades. 'n Uiteensetting word verskaf van hoe die Sentrum inderdaad die hoof inisiatief vir die behaal van die ooreengekome nasionale doelstellings kan word. Die gevolgtrekking is dat belegging deur # This article is an extension of a paper presented at

To increase the acceptance of direct metal laser sintered Ti6Al4V(Extra Low Interstitial—ELI) in industry, analytical models that can quantitatively describe the interrelationships between the microstructural features, field variables, such as temperature and strain rate, and the mechanical properties are necessary. In the present study, a physical model that articulates the critical microstructural features of grain sizes and dislocation densities for use in predicting the mechanical properties of additively manufactured Ti6Al4V(ELI) was developed. The flow stress curves of different microstructures of the alloy were used to obtain and refine the parameters of the physical model. The average grain size of a microstructure was shown to influence the athermal part of yield stress, while the initial dislocation density in a microstructure was seen to affect the shape of the flow stress curve. The viscous drag effect was also shown to play a critical role in explaining the upturn of flow stress at high strain rates. The microstructure-based constitutive model developed and validated in this article using experimental data showed good capacity to predict the high strain rate flow properties of additively manufactured Ti6Al4V(ELI) alloy.

Dislocations play a central role in determining strength and flow properties of metals and alloys. Diffusionless phase transformation of β→α in Ti6Al4V during the Direct Metal Laser Sintering (DMLS) process produces martensitic microstructures with high dislocation densities. However, heat treatment, such as stress relieving and annealing, can be applied to reduce the volume of these dislocations. In the present study, an analysis of the X-ray diffraction (XRD) profiles of the non-heat-treated and heat-treated microstructures of DMLS Ti6Al4V(ELI) was carried out to determine the level of defects in these microstructures. The modified Williamson–Hall and modified Warren–Averbach methods of analysis were used to evaluate the dislocation densities in these microstructures. The results obtained showed a 73% reduction of dislocation density in DMLS Ti6Al4V(ELI) upon stress relieving heat treatment. The density of dislocations further declined in microstructures that were annealed at elevated temperatures, with the microstructures that were heat-treated just below the β→α recording the lowest dislocation densities.

The characterisation and monitoring of Ti6Al4V (ELI) feedstock powder is an essential requirement for the full qualification of medical implants and aerospace components produced in selective laser melting systems. Virgin and reused samples of this powder were characterised by determining their physical and chemical properties through techniques complying with international standards. This paper presents the results obtained for Ti6Al4V (ELI) powder of two different particle size distributions received from the same supplier. The characteristics of these powders after several reuse cycles in two different selective laser melting systems are also presented and discussed. OPSOMMINGDie karakterisering en kontrolering van Ti6Al4V voermateriaalpoeier is ʼn kernvereiste vir die kwalifisering van mediese implantate en ruimtevaartkomponente wat deur middel van selektiewe laser smelt stelsels produseer word. Nuwe en herbruikte monsters van hierdie poeier is gekarakteriseer deur hul fisiese en chemiese eienskappe te bepaal deur tegnieke wat aan internasionale standaarde voldoen. Die resultate vir Ti6Al4V poeiers met verskillende partikelgrootteverdelings van dieselfde verskaffer word hier voorgehou. Die karakteristieke van hierdie poeiers na etlike hergebruik siklusse in twee verskillende selektiewe laser smelt stelsels word ook voorgehou en bespreek.

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