Structurally Graded Refractory High Entropy Alloys Through Laser Tuning

High Entropy Alloys (HEAs) represent a transformative class of materials characterized by their complex, multi-principal element compositions and properties exceeding those of conventional alloys. Among HEAs, Refractory High Entropy Alloys (RHEAs) stand out due to their remarkable thermal stability and mechanical strength, making them ideal candidates for the next-generation high-temperature applications in aerospace, nuclear, and defense industries. However, tailoring the microstructure and properties of RHEAs through processing to meet specific performance criteria remains a significant challenge.<br/><br/>Efforts in materials discovery increasingly rely on high-throughput computational and experimental techniques to stimulate the exploration of complex alloy systems, such as HEAs. High-throughput methodologies enable rapid screening of compositional spaces, accelerating the identification of promising chemical compositions with desired properties. Among various high-throughput screening methods laser metal deposition by directed energy deposition (DED) emerges as a technique that scales up to the bulk materials. By using multiple powder lines it enables obtaining graded structures using various mixing and printing strategies.<br/><br/>In the present work additive manufacturing by DED was used to fabricate structurally graded RHEAs from the Nb-Ti-Zr system. The ultrasonically atomized powder was deposited on various build plates acting as a reservoir for alloying elements. Optimization of printing parameters resulted in graded structure and properties along the build direction of the alloy. The compositional and structural changes were examined using scanning- and transmission electron microscopy. To explain the thermodynamics of solidification processes the calculation of phase diagrams (CALPHAD) method was utilized using Thermo-Calc software.<br/><br/>Our research demonstrates that laser tuning offers a powerful and flexible tool for developing structurally graded RHEAs with customizable properties. This advancement scales up the alloy design process and accelerates bulk-scale screening for alloys with enhanced properties and performance.