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Laser Metal Deposition of Ultra-Fine Duplex AlCrFe2Ni2-Based High-Entropy Alloy

: Molina, Veronica Rocio; Weisheit, Andreas; Gein, Sergej; Hecht, Ulrike; Vogiatzief, Dimitrios

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Frontiers in Materials 7 (2020), Art. 275, 10 S.
ISSN: 2296-8016
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer ILT ()
Laser Material Deposition; high-entropy alloy; AlCrFeNi alloy; Additive Manufacturing; duplex microstructure

A duplex, nano-scale Co-free high-entropy alloy (HEA) based on AlCrFe2Ni2 wasprocessed using laser material deposition (LMD). Process parameters in various beamdiameter configurations, as well as deposition strategies, were used while the alloymicrostructure was investigated in the as-built and heat-treated condition. Interlayerregions present a duplex microstructure composed of ultra-fine face-centered cubic(FCC)-platelets nucleated in a nano-scale structured body-centered cubic (BCC) phase.Rapid cooling during LMD induces the decomposition of the BCC phase into orderedand disordered nano-scaled structures. The hard and brittle BCC phase yields a highcrack susceptibility during rapid cooling in the LMD process. A suitable processingstrategy paired with a post-processing heat treatment was developed to solve thischallenge. After heat treatment at 900 C and 6 h annealing time with subsequentfurnace cooling, the material presented a homogeneous duplex ultra-fine FCC/BCCmicrostructure and high bending strength (2310 MPa) compared to a heat-treatedcast duplex-steel (1720 MPa) while maintaining excellent ductility (no failure at 20%bending strain).