Abstract
Extending the concept of complex concentrated alloys (CCAs) to the refractory alloys (solidus temperature over 2000 °C) space potentially facilitates the design of lightweight structural alloys with service temperatures that exceed those of Ni and Co-based alloys. However, the room and elevated temperature tensile properties of the current refractory-CCAs (R-CCAs) are inferior to those of the Ni/Co-based alloys. Furthermore, the manufacturing scalability of R-CCAs remains challenging, in that cracks are prevalent in all R-CCAs when processed using near-net shape manufacturing processes, such as fusion-based additive manufacturing (F-BAM). Still, mechanisms governing the poor F-BAM processability of R-CCAs remain unexplored. To this end, this work unveils the atomistic mechanisms underlying F-BAM process-induced cracking in a NbTiTaMoHfZrC R-CCA. The implications of light elements’ presence for intrinsic ductility and grain boundary cohesion, and subsequently for F-BAM processability and mechanical behavior, are revealed. Leveraging the insights, we accomplish what is, to the best of the knowledge, the first instance of crack-free F-BAM processing of any R-CCA. Additionally, the R-CCA exhibits over 20% tensile ductility and ≈160 MPa tensile yield strength at 1200 °C. In addition to facilitating the design of lightweight R-CCAs, findings enable scalable manufacturing of these ultra-high temperature alloys for structural applications.
| Original language | English |
|---|---|
| Journal | Advanced Functional Materials |
| DOIs | |
| State | Accepted/In press - 2025 |
Funding
Research was sponsored by the US Department of Energy, Advanced Research Projects Agency – Energy (ARPA‐E) under contract DE‐AC05‐00OR22725 with UT‐Battelle LLC and performed in partiality at the Oak Ridge National Laboratory's Manufacturing Demonstration Facility, an Office of Energy Efficiency and Renewable Energy user facility. Much of the microscopy presented in this work was performed with the support of Carl Zeiss via a cooperative research and development agreement (NFE‐19‐07705). All APT and S/TEM preparation and experimental work was conducted at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors thank Jeffrey Baxter, Sarah Graham, Ryan Duncan, and Charles Hawkins for assistance with FIB milling, metallography, machining, and mechanical testing, respectively.
Keywords
- additive manufacturing
- complex concentrated alloys
- density functional theory
- grain boundary cohesion
- grain boundary segregation
- mechanical behavior
- refractory alloys