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

• Published in: Frontiers in materials 2020-08, Vol.7
• Main Authors: Molina, Veronica Rocio, Weisheit, Andreas, Gein, Sergej, Hecht, Ulrike, Vogiatzief, Dimitrios
• Format: Article
• Language: English
• Subjects: additive manufacturing; AlCrFeNi alloy; duplex microstructure; high-entropy alloy; laser material deposition
• ISSN: 2296-8016; 2296-8016
• DOI: 10.3389/fmats.2020.00275

A duplex, nano-scale Co-free high-entropy alloy (HEA) based on AlCrFe2Ni2 was processed using laser material deposition (LMD). Process parameters in various beam diameter configurations, as well as deposition strategies, were used while the alloy microstructure was investigated in the as-built and heat-treated condition. Interlayer regions 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 ordered and disordered nano-scaled structures. The hard and brittle BCC phase yields a high crack susceptibility during rapid cooling in the LMD process. A suitable processing strategy paired with a post-processing heat treatment was developed to solve this challenge. After heat treatment at 900°C and 6 h annealing time with subsequent furnace cooling, the material presented a homogeneous duplex ultra-fine FCC/BCC microstructure and high bending strength (2310 MPa) compared to a heat-treated cast duplex-steel (1720 MPa) while maintaining excellent ductility (no failure at 20% bending strain).