Design and characterization of novel TiAl alloys and metal-diamond composites for beam-based additive manufacturing

  • Date: Nov 10, 2015
  • Time: 11:00 AM - 12:00 PM (Local Time Germany)
  • Speaker: Dr. Christian Leinenbach
  • Laboratory for Joining Technologies and Corrosion EMPA - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
  • Room: Seminar Room 1
  • Host: Prof. Dierk Raabe
Metal additive manufacturing (AM) techniques are powder-based, layer by layer methods which can directly build 3D structures onto substrates with complex geometries. They offer a unique ability to dynamically mix materials during the deposition process and produce functionally graded structures, new composite microstructures and perhaps even new material classes. Some of the challenging issues related to the energy beam based process are the very high heating and cooling rates, leading to non-equilibrium microstructures, which are usually harder, less ductile, and often exhibit high residual stresses; the strongly textured, anisotropic microstructures inherited from the solidification conditions; or the pronounced residual stresses resulting from the large thermal gradients in the AM fabricated parts. However, the very rapid consolidation of the material in a small material volume and the achieved high solidification rates allow for the manufacture of components containing meta-stable materials. In this talk some relevant results of the AM related research at Empa will be presented. The first part of the presentation deals with the development and characterization of a novel oxide dispersion strengthened (ODS) titanium aluminide alloy (Ti-45Al-3Nb ODS) for beam-based AM processes. The alloy design and selection process was supported by computational thermodynamics based on the CALPHAD approach, taking into account requirements for processing as well as long term alloy behavior under service conditions. Besides, an in situ method to study the behavior of alloys during rapid heating and cooling combining laser heating with synchrotron micro X-ray diffraction (microXRD) and high-speed imaging was developed. In the second part, the feasibility of producing metal-diamond composites by SLM was studied. A Cu-Sn-Ti alloy powder was mixed with 10-20 vol.% artificial, mono-crystalline diamonds. The influence of the processing parameters on the density and microstructure of the composites as well as on the stability of the diamonds was studied. It was shown that stable specimens containing intact diamonds could be produced.
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