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Combining Thermodynamic Modeling and Additive Manufacturing for High-Throughput Screening of Compositionally Complex Alloys

Wednesday (26.09.2018)
15:15 - 15:30 S1/01 - A5
Part of:

Using the alloying concept of single-phase high entropy alloys (HEAs) as a basis for new compositionally complex alloys (CCAs) provides the opportunity to design metals with exceptional mechanical properties. However, selecting specific CCAs with desired properties is a challenging task as a result of the vast alloying space of CCAs with five or more principle elements. So far, steps in the direction of CCA screening are seldom and time-consuming manufacturing methods hinder efficient development of promising alloys.

Therefore, a methodology is introduced which enables high-throughput screening and design of CCAs by combining theoretical and experimental approaches, thereby focusing on the Al-C-Co-Cr-Fe-Mn-Ni system. First, a new thermodynamic database for CALPHAD calculations was compiled for the alloying system, which is subsequently used to identify composition ranges for multiphase microstructures with the possibility of precipitates after heat treatment. Secondly, samples with the chemical compositions suggested by the theoretical screening are synthesized by laser metal deposition (LMD). By combining the use of elemental powder blends and in-situ alloying in LMD, the flexibility to rapidly manufacture samples with differing chemical composition is maximized. Thirdly, materials characterization of specimens is split into light and deep screening. In the light screening step, comparatively fast methods, such as XRD phase analysis, hardness and compression testing, are used to reduce the number of promising candidates for the following step. In deep screening, advanced methods, such as SEM, EDX, EBSD and tensile testing, are utilized to evaluate the microstructure and the resulting mechanical properties in detail.

Phase constitution after heat treatment of LMD samples were correctly predicted by the calculations with the developed CALPHAD database. Alloys selected in the fast screening step provided a sound base to speed up the alloy selection process, as the identified properties translated reliably into the deep screening step. The applicability of the introduced methodology for identifying promising CCAs as well as microstructural and mechanical properties in the Al-C-Co-Cr-Fe-Mn-Ni alloying system are discussed.

Fabian Kies
RWTH Aachen University
Additional Authors:
  • Dr. Bengt Hallstedt
    RWTH Aachen University
  • Dr. Christian Haase
    RWTH Aachen University