Burghardt Klöden

Process window for electron beam melting of Ti-6Al-4V

Selective electron beam melting (EBM) is a powder-bed based additive manufacturing technique for the fabrication of dense metallic parts. As a free-form deposition process EBM offers a high degree of freedom in design and a highly efficient utilization of material. For a widespread industrial application the achievable build rate is a critical factor. In this paper the process window for Ti-6Al-4V is explored by varying beam current and scan speed in a wide range. The EBM specimens were characterized by their density, porosity size and distribution, chemical composition, microstructure, hardness and tensile strength. Key findings include: (1) the minimum line energy necessary to achieve full density, (2) parameter sets for increased build rates at full density, and (3) formation of α-martensite at high scan rates.

High-entropy alloy CoCrFeMnNi produced by powder metallurgy

ABSTRACT Lately high-entropy alloys (HEAs) have been the topic of extensive research, as these materials are promising candidates for many challenging applications, as for example tools, moulds and functional coatings. In contrast to conventional alloys, HEAs consist of five or more principal elements, each having a concentration between 5 and 35u2005at.-%. Against expectations, HEAs show a rather simple microstructure consisting preferentially of cubic phases. Due to this microstructure, HEAs show promising properties, e.g. in terms of 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 efficiency and high shape complexity. Gas atomised powder was used and selected PM methods are presented (e.g. pressureless sintering, spark plasma sintering, additive manufacturing (EBM)). The process methods were evaluated by characterising the material properties (density, microstructure, mechanical properties) of the compacted and sintered samples.

Mechanical Properties of Ti-6Al-4V Fabricated by Electron Beam Melting

Powder bed additive manufacturing of titanium components offers several advantages. The high freedom of design enables the fabrication of structurally optimized, lightweight parts. Complex geometries may serve additional functions. The use of additive manufacturing has the potential to revolutionize logistics by dramatically reducing lead time and enabling a high degree of customization. Manufacturing near net shape parts reduces the loss of expensive material.For the application in safety relevant parts certainty about static and fatigue strength is critical. A challenge arises from complex influences of built parameters, heat treatments and surface quality. Ti-6Al-4V specimen built by electron beam melting (EBM) were subjected to heat treatments adapted to various employment scenarios. The results of tensile and fatigue testing as well as crack propagation and fractography will be compared to titanium manufactured conventionally and by selective laser melting (SLM). The mechanical behavior will be correlated to the microstructural evolution caused by the heat treatments