Advances in Multi-Principal Elements Alloys X: Alloy Development and Properties: Alloy Development and Application III
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical

Tuesday 2:30 PM
March 1, 2022
Room: 251A
Location: Anaheim Convention Center

Session Chair: Yanwen Zhang, Idaho National Laboratory; William Weber, University of Tennessee

2:30 PM  Invited
Discovery of New Refractory High-entropy Alloys with Improved High-temperature Properties: Stephen Giles1; Debasis Sengupta1; Scott Broderick2; Krishna Rajan2; Peter Liaw3; 1CFD Research Corp; 2University at Buffalo; 3University of Tennessee, Knowxville
    Refractory high-entropy alloys (RHEA) are a promising class of alloys that show elevated-temperature yield strengths and have potential to use as high-performance materials in gas turbine engines. However, exploring the vast RHEAs compositional space experimentally is challenging, and only a small fraction of this space has been explored to date. The work demonstrates the development and use of a framework by coupling the state-of-the-art machine learning and optimization methods to intelligently explore the vast compositional space and drive the search in a direction that improves high-temperature yield strengths. On development of a robust yield strength prediction model, the coupled framework is used to discover new RHEAs with superior high temperature yield strength. We have shown that one can customize a RHEA composition to have maximum yield strength at a specific temperature. The model predictions are validated against experiments.

2:50 PM  Invited
Multi-principal Elements Alloys as Filler Metals for Similar and Dissimilar Joining Applications: Zhenzhen Yu1; Benjamin Schneiderman1; Abdelrahman Abdelmotagaly1; Andrew Chuang2; 1Colorado School of Mines; 2Argonne National Laboratory
    Multi-principal elements alloys (MPEA) have a vast compositional space available. Their tendency to form entropy-stabilized, simple solid solution phases, and to exhibit composition-dependent sluggish diffusion characteristics, make them potential candidates as filler metals for similar and dissimilar joining. One application example is brazing of Ni-base superalloys. A new filler, MnFeCoNiCu, was designed using a high-throughput computational methodology. The microstructural evolution during brazing was systematically investigated by ex-situ and in-situ characterizations and kinetic analysis. It was found out that Cu and Mn segregation into interdendritic region served to increase lattice parameter disparity between dendritic and interdendritic regions during early stage of solidification. Solid-state interdiffusion facilitated composition homogenization during cooling. Exceptional mechanical properties have been demonstrated in the brazed joints in comparison to these made with conventional fillers. Additional examples will be shown to demonstrate the effectiveness of MPEA fillers designed for weld defect control and dissimilar materials joining.

3:10 PM  
A Novel Approach to Designing Low-density CCAs Exploiting Multi-element Eutectics: Clemens Simson1; Stefan Gneiger1; Alexander Großalber1; Stefan Pogatscher2; 1LKR Light Metals Technologies Ranshofen; 2Montanuniversität Leoben
     In recent years, several multi-principle element alloys (MPEAs) and compositionally complex alloys (CCAs) have been derived from the high entropy concepts. Their often outstanding mechanical- and physical properties can be attributed to an intrinsic nanoscale microstructure. While many examples are shown for transition- or refractory metal-based systems, the concept of multi-principal element solid solutions could not be successfully transferred into light metal-based systems yet, due to their strong tendency to form ordered intermetallic phases. In our work, we show that equilibrium sub-micron eutectic structures can be achieved in the vicinity of lower order invariant points of higher order systems. We suggest that this rescaling can be attributed to the inherent thermodynamic frustration compared to Gibbs’ rule of phases. Multiple examples of Al- and Mg- based ternary and quaternary compositions are given and compared against their respective CALPHAD predictions. Additionally, strategies for exploring higher-dimensional systems are discussed.

3:30 PM  
Microalloying Technology: A Promising Strategy for Design of Nanocrystalline High-entropy Alloy Films: Wenyi Huo1; Feng Fang2; Zonghan Xie3; Hyoung Seop Kim4; Jianqing Jiang1; 1Nanjing Forestry University; 2Southeast University; 3University of Adelaide; 4Pohang University of Science & Technology (POSTECH)
    In the manufacturing engineering for nanofabricated devices, polycrystalline metal thin films are indispensable as electrical resistors and structural elements. However, it is still a daunting task to design such metal films with structural and functional properties (e.g., hardness and resistivity) combined. High-entropy alloy film is considered as a promising candidate material suitable to go further in the simultaneous enhancement of both mechanical and electrical properties of thin film resistor. In this work, the remarkable microalloying (<2.0 at.%) enhancement in several sputtered CoCrFeNi high-entropy alloy films was investigated from a multitechnique approach. High resolution transmission electron microscope characterization shows in particular that there are unusual multifold nanotwins, and nanoscale polytypes. The knowledge of the relationship between structure and properties of such new materials is explored.

3:50 PM Break

4:10 PM  
Synthesis and Characterization of Porous AlCoCrFeNi High-entropy-alloy: Akib Jabed1; Golden Kumar1; 1The University of Texas at Dallas
    Porous metals are desirable in applications that require low density, high strength to weight ratio, and large specific area. High-entropy-alloys (HEA) is a new family of metal alloys that exhibit high strength, ductility, and fracture toughness due to the formation of multi-element solid solution. Here, we report the synthesis of porous AlCoCrFeNi HEA by combining the space filler and powder metallurgical approaches. The HEA powders with different fillers and compacted, sintered, and characterized. The effects of processing parameters on the density, the microstructure, and the mechanical behavior are investigated. The results are compared with the fully dense samples made by casting.

4:30 PM  
Expanding the Design Space of Ti-V-Nb-Hf Refractory High-entropy Alloys through Al-alloying : Shaolou Wei1; Cem Tasan1; 1Massachusetts Institute of Technology
    Because of their promising yield preservation trend at elevated temperatures, refractory high-entropy alloys (RHEAs) have drawn increasing attention in seeking optimal mechanical performances and exploring the underlying physical foundations. However, the apparent brittleness at ambient temperature, the necessity of extensive thermo-mechanical processing, and the presence of catastrophic oxidation, still remain serious challenges. Our previous work has detailed the development of a Ti-V-Nb-Hf RHEA family that exhibits promising tensile ductility at room temperature. In this presentation, we aim to further explore the property design space of this particular RHEA system via Al alloying. The following three topics will be revealed in greater depth: (1) how much intrinsic strengthening (or softening) is associated with Al alloying? (2) how will dislocation plasticity micro-mechanisms vary in response to Al alloying? and (3) how does Al modulate the phase stability and thereby precipitation pathways at intermediate temperatures?