The award is sponsored by Taylor & Francis Group.
EPMA Keynote Papers for World PM2016 are: (from left to right) Dipl.-Ing. Daniel Schwenck, Mr Yuu Akiyama, Dr Thomas Ebel, Mr Alexander Angré, Dipl.-Ing. Dominik Bauer, Dr Jean-Michel Missiaen, Dipl.-Ing. Nadine Eiβmann, (Co-author pictured, Prof Dr Bernd Kieback)
A Novel Convergent-Divergent Annular Nozzle Design for Close-Coupled Atomization
by Dipl.-Ing. Daniel Schwenck (University of Bremen, Germany)
Additive manufacturing processes such as SLM require small particle sizes. A widely used technique to produce suitable powders is close coupled atomization. To further decrease the achieved particle sizes the annular geometry of the gas nozzle is changed to a convergent divergent profle. This novel confguration is capable to operate stable at low pressures of 0.8 MPa and above. Beyond that, the unwanted process affection from lick-back is avoided. Different nozzles with conventional and convergent-divergent annular geometry have been designed based on ﬂuid ﬂow calculations. The aspiration pressure was measured to determine stable process windows. Powders from a CuSn bronze were then produced using cold and hot gas atomization to show the inﬂuence on the process stability, particle size, and morphology. High speed recordings are used to investigate the process conditions of the different nozzle confgurations.
Investigations of Aging Behaviour From Aluminum Powders During Atmosphere Simulation of the LBM Process
by Dipl.-Ing. Dominik Bauer (Airbus Group Innovations, Germany)
Additive layer Manufacturing (ALM) offers for production of parts and components for aeronautic applications potential cost benefts over conventional manufacturing routes. In particular, powder bed processes offer a high degree of design ﬂexibility while enabling weight reduction due to topological optimization. Quality and properties of the parts are strongly dependent on the powder quality which, in turn, is inﬂuenced by handling and storage of the powder.
For the investigations aluminum powder (Al-Si-Mg) was aged under atmosphere of different moistures and temperatures for defned duration. As well as the ﬂowability on behave of this inﬂuence was investigated. The effect of vacuum drying on the ﬂowability was investigated. Prior to this the chemistry of the powder was measured by inductively coupled plasma optical emission spectrometry (ICP-OES) and carrier gas hot extraction. The morphology was evaluated by scanning electron microscope (SEM). Results clearly demonstrate the feasibility to reuse dried condensed powders.
Phase Transformation Under Isostatic Pressure in HIP
by Mr Alexander Angré (Swerea KIMAB, Sweden)
The new cooling systems in hot isostatic presses enables fast cooling rates under isostatic pressure. This does not only enable shorter HIP cycles but also allow complete heat treatment cycles to be performed in one HIP cycle. It has been shown in previous studies that extreme pressures of a few thousand MPa can push phase transformation toward longer times. The new URQ HIP cooling systems give the opportunity to investigate the impact of isostatic pressures up to 200MPa on phase transformation time dependency. For this study two materials have been used. For each material a comparison of ferrite/pearlite/bainite phase transformation time at 10MPa and 170MPa was performed. The study was performed by isothermal heat treatment of specimens for a specifc time followed by quenching. To evaluate the inﬂuence of pressure on hardenability, phase fractions were estimated optically in SEM and LOM. The study found signifcant inﬂuence of pressure on hardenability.
Reduction of the Embrittlement Effect of Binder Contamination in MIM Processing of Ti-Alloys
by Dr Thomas Ebel (Helmholtz-Zentrum Geesthacht, Germany)
During MIM processing titanium tends to react with carbon from the polymeric binder. Preferentially at the grain boundaries large carbides are formed leading to embrittlement of the sintered material. Especially in beta-titanium alloys this is a critical issue, because beta phase stabilizing elements like V, Mo and Nb decrease the carbon solubility of the Ti-matrix, thus, carbides precipitate already at rather low carbon contents. In this study a Ti-22wt%Nb alloy was processed by MIM. Adding Zr led to a signifcant reduction of the amount of carbides formed due to an increase in the lattice constant and, thus, an increase of the carbon solubility. Furthermore, boron was added to achieve grain refnement which additionally, supports a fner distribution of the carbides. SEM and TEM investigations reveal the role of the elemental additions and analyse the structure of the different carbides formed. In summary, a signifcant increase of ductility could be achieved.
EBSD Study of WC Grain Boundaries in WC-Co Alloys. Effect of Co Content and Carbon Potential
by Dr Jean-Michel Missiaen (Grenoble INP, France)
The mechanical strength of WC-Co alloys is closely related to the physical properties of WC and Co and to their distribution and size in the material. WC grains form a more or less continuous skeleton in a Co matrix. A lot of work was devoted to the characterization and modelling of WC grain boundaries to understand their formation and their effect on the material properties. It is well established that the area fraction of grain boundaries decreases when Co content increases. This study aims in characterizing the grain boundary structure as a function of cobalt content and carbon potential using EBSD technique complemented by TEM. Boundary habit planes were estimated using stereology. Grain boundary orientations were classifed in four families, the rotation angle distribution was determined in each set and compared with the powder. Although a few special grain boundaries originate from the powder, most grain and phase boundaries are formed during heat treatment. The mechanisms of grain boundary and phase boundary formation and migration are discussed, based on the experimental results. The occurrence of grain boundaries with special orientations and/or remarkable habit planes is especially enlightened. Finally, the role of grain boundaries on the mobility of WC/Co phase boundaries is discussed and it can explain the observed enhancement of grain growth with increasing binder content.
Development of Synchronizer Hub with Helical Gear for DCT
by Mr Yuu Akiyama (Sumitomo Electric Sintered Alloy Ltd, Japan)
This product is a synchronizer hub for low speed applied to seven steps DCT (Dual Clutch Transmission) for Hybrid Electric Vehicle. For DCT, there are remarkable features, one is computer-controlled automatic shifting like CVT (Continuously Variable Transmission) or AT (Automatic Transmission), and another one is high transmission effciency as much as MT (Manual Transmission) due to no torque converter which contributed to low fuel consumption. However, weight and cost reduction for DCT are also required because of its complicated structure and huge number of components. So we developed a high strength synchronizer hub with helical gear and thin wall by P/M process.
High-Entropy Alloy CoCrFeMnNi Produced by Powder Metallurgy
by Dipl.-Ing. Nadine Eiβmann (Technical University Dresden, Germany)
Lately high-entropy alloys (HEAs) have been the topic of extensive research, as these materials are promising candidates for many challenging applications, as for examples tools, moulds and functional coatings. In contrast to conventional alloys, HEAs consist of fve or more principal elements, each having a concentration between 5 and 35 at-%. Against expectations, HEAs show a rather simple microstructure consisting preferentially of cubic phases. Due to this microstructure, HEAs show promising properties, as for example high-temperature stability, high strength and ductility. Within this research, a single-phase CoCrFeMnNi HEA was produced by powder metallurgy (PM). In contrast to conventional metallurgy, PM offers a lot of advantages, e.g. good material effciency and high shape complexity. Gas atomized powder was used and selected compaction methods are presented (e.g. pressureless sintering, spark plasma sintering). The process methods were evaluated by characterizing the material properties (density, microstructure, mechanical properties) of the compacted and sintered samples.