HEA 2023: Processing, Microstructure, and Properties of HEAs II
Program Organizers: Andrew Detor, DARPA/DSO; Amy Clarke, Los Alamos National Laboratory
Wednesday 9:00 AM
November 15, 2023
Room: Three Rivers
Location: Omni William Penn
Session Chair: Easo George, University of Tennessee
9:00 AM Introductory Comments
9:05 AM Invited
Controlling the Sources of Interstitial Constituents in Refractory Complex Concentrated Alloys: Calvin Belcher1; Sakshi Bajpai1; Vivek Verma1; Benjamin MacDonald1; Diran Apelian1; Enrique Lavernia1; 1University Of California Irvine
Recent findings reveal that interstitial constituents, especially oxygen and nitrogen, inadvertently introduced in refractory complex concentrated alloys (RCCAs) significantly contribute to, and convolute observations of, ductility and strength of the alloys at room temperature. Plasma arc melting (PAM) has facilitated the quest for RCCAs showcasing remarkable blends of strength and ductility. In this work, we studied the composition and chemistry of residual gases in the PAM chamber environment during arc melting using a mass spectrometer to better quantify methodologies utilized to control sources of oxygen and nitrogen, in arc melted RCCAs. Moreover, thermodynamic mechanisms of the absorption of interstitial constituents was investigated by arc melting MoNbTaW and NbTiZr RCCAs. With respect to interstitial constituents, the RCCAs were characterized using electron microscopy and atom probe tomography. Correlations between the microhardness and microstructures of the RCCAs aided elucidation of the influence of the interstitial constituents on the mechanical properties of the RCCAs.
9:35 AM
Complex Concentrated Alloys with Architectured Microstructures: A New Design Strategy for High-temperature Applications: Jean-Philippe Couzinie1; Loic Perriere1; Ines Crouzet1; Regis Poulain1; Frederic Prima2; Guy Dirras1; 1CNRS; 2IRCP
Over the last two decades, efforts have been made to break with the conventional alloy design and the concept based on multi-principal elements has raised a lot of attention. Thanks to their capacity to maintain high strength properties for T>1000°C, refractory complex concentrated alloys (RCCAs) have received attention for high-temperature (HT) applications. Promising compositions are found in alloy systems with intermetallic B2 phase together with disordered BCC phase. However, and in addition to the microstructural instability, most of those materials have been observed to lose their HT strength above 0.6Tm. Another way to push the boundaries is the formation of architectured microstructures in these complex alloys. To do so, an option is the use of interface-driven microstructures with finely distributed phases. In that way, the development of eutectic RCCAs can meet with this challenge and the design strategy will be discussed in light of recent results gathered by our consortium.
9:55 AM
Deformation Behavior and Damage Evolution in AlCoCrFeNi2.1 Eutectic High Entropy Alloys: Cal Siemens1; Jidong Kang2; David Wilkinson1; 1McMaster University; 2CanmetMATERIALS
The AlCoCrFeNi2.1 eutectic HEA (EHEA) is a duplex casting alloy exhibiting high strength and moderate ductility. However, there is currently little work published on mechanisms controlling damage and fracture for this EHEA. A series of EHEAs were fabricated including as-cast and hot rolled variants, plus one with increased Fe content (termed the Fe-EHEA). In-situ techniques involving micro-digital image correlation and x-ray computed tomography were used to characterize the distribution of deformation and damage evolution at the microscale while under strain. These methods were paired with scanning electron microscopy and fracture toughness measurements to determine phase composition and defect sensitivity. Micro-crack nucleation and early strain localization were found to be controlling fracture mechanisms for the cast alloys. The Fe-EHEA was found to exhibit improved phase co-deformation and elongation to fracture, while maintaining tensile strength, when compared to the base EHEA composition. This work showcases fine-tuning HEA composition to tailor mechanical properties.
10:15 AM Cancelled
Microstructure and Mechanical Properties of Mo-Nb-Ti-V-W-Zr Refractory High Entropy Alloys Developed using a Data-driven Inverse Alloy Design approach: Lavanya Raman1; Marcia Ahn1; Arindam Debnath1; Shuang Lin1; Adam Krajewski1; Shunli Shang1; Wesley Reinhart1; Allison Beese1; Bed Poudel1; Zi Kui Liu1; Shashank Priya1; Wenjie Li1; 1Pennsylvania State University
The concept of heterogeneous/composite microstructure has proved as an effective approach in achieving an optimum combination of high strength and ductility. In MoNbTaW-containing refractory high entropy alloys, adequate strength and ductility are reported by the addition of V and Zr by tailoring the microstructure. Our work generates the desired compositions using high-throughput computational, machine-learning models, and inverse design. The selected compositions based on elements Mo-Nb-Ti-V-W-Zr are manufactured utilizing vacuum arc melting and field-assisted sintering technology. The phase formation is correlated using CALPHAD. ML models are used to predict the mechanical properties of the alloy and are validated with experimental mechanical data obtained from the three-point bend and compression tests. The deformation of different phases is also understood from nanoindentation studies. The effect of the synthesis route on the phase formation and mechanical data is also established. The interactive design strategy adopted is applicable to other materials systems including HEAs.
10:35 AM Break
10:55 AM
Assessing Additive Manufacturing Processability of Novel Refractory High Entropy Alloys Prior to Powder Manufacture: Lucy Farquhar1; Hugh Banes1; Lova Chechik2; Alex Goodall1; Prashant Jadhav1; Abdallah Reza3; Felix Hofmann3; Iain Todd1; Russell Goodall1; 1University Of Sheffield; 2Friedrich-Alexander-Universität Erlangen-Nürnberg; 3The University of Oxford
Many high entropy alloys (HEAs) have been manufactured by additive manufacturing (AM), resulting in components with excellent build quality. However, AM processes require controlled feedstock materials, and screening HEAs for AM processability is time consuming and costly. For refractory HEAs especially, bespoke powders can also be difficult to manufacture with huge associated costs and lead times. This work presents an alloy processability assessment for the laser powder bed fusion (LPBF) process, to be used prior to welding trials or expensive powder manufacture. CALPHAD analysis is used along with Rosenthal based simulations to predict the alloy susceptibility to solidification and solid state cracking. These results are then compared with experimental weld tracks and LPBF of CoCrFeNi-based HEAs and with the cracking behaviour of some commonly processed commercial alloys. The method is then used to predict AM processability of some novel refractory HEAs, one of which is then successfully manufactured by LPBF.
11:15 AM
High-throughput Design, Synthesis, and Characterization of Refractory High Entropy Alloys (RHEAs): Cafer Melik Ensar Acemi1; Eli Norris1; William Trehern1; Brent Vela1; Raymundo Arroyave1; Ibrahim Karaman1; 1Texas A&M University
Refractory alloys are promising for high-temperature applications because of their high strength at elevated temperatures, high thermal conductivity, low thermal expansion coefficient, and operability under oxidizing conditions. One hundred twenty-five refractory high entropy alloys (RHEAs) have been designed to exhibit single BCC phase at elevated temperatures, target yield strength (>200 MPa) at 1300°C, density (<9 gr/cc), thermal conductivity (>9 W/mK), linear thermal expansion (<2%) between ambient and 1300 ℃, and narrow solidification range for additive manufacturability. Designed compositions are synthesized with high-throughput vacuum arc melting and characterized via electron microscopy (SEM/EDX), XRD, Vickers microhardness, nanoindentation, compression, tension, thermal transport, and thermal expansion experiments. In as-cast state, all samples had BCC phase with dendrites. Homogenization heat treatments at 1800°C and 1925°C are performed based on diffusion calculations centered around the compositional difference and dendrite arm spacing. Compression/tension experiments are then performed at high temperatures to compare with the predicted high-temperature properties.
11:35 AM
The Fundamentals of Recrystallization in Binary Niobium Alloys: William Waliser1; Nelson Delfino de Campos Neto1; Nathan Peterson1; Noah Philips2; Matt Carl2; Kester Clarke1; Amy Clarke1; 1Colorado School Of Mines; 2ATI metals
Nb3Sn superconductor wires are the leading option for next-generation particle accelerator magnets, which require heat treatment. Additions of Hf to Nb precursor alloys assist in maintaining finer grain sizes, which result in increased superconductor performance. However, increased demand and reliance on constrained resources such as Hf poses sustainability concerns for future projects, i.e. Future Circular Collider and the development of refractory multi-principal element alloys (RMPEAs). To identify cost effective alternatives, a series of binary Nb-X alloys, including X=Ti, Zr, Hf, V, Ta, Mo, W, and Re, were fabricated and cold rolled to observe the effects of composition and deformation energy on recrystallization and grain growth processes. Samples were heat treated and resulting microstructures were characterized. Thermomechanical processability and mechanical properties of the alloys were also assessed. These results will inform the development of RMPEAs for superconductor and aerospace applications.
11:55 AM
Lightweight Refractory High Entropy Alloy With Extreme Ductility: Saurabh Nene1; Aditya Balpande1; Akshit Dutta1; 1Indian Institute of Technology Jodhpur
Refractory high entropy alloys (R-HEAs) have gained enormous attention owing to their extreme chemical stability and high strength at elevated temperatures. However, they exhibit very limited formability at room temperature (RT) and extremely high cost and density thereby limiting their applications. Here we present a refractory Ti58-x-yZr16V16Nb10AxMoy high entropy alloy (Ti-HEA) having a very low density of 5.6 g/cc and extreme tensile ductility of 50 % at RT along with the yield strength of 1.1 GPa. The excellent property profile of Ti-HEA is attributed to the smart design strategy adopted for Ti-HEA which involves combination of HEA, valence electron configuration theories thereby activating slip dominated deformation in single phase β-b.c.c. equiaxed micro-structure in-as-cast state.