skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Ink‐Extrusion 3D Printing and Silicide Coating of HfNbTaTiZr Refractory High‐Entropy Alloy for Extreme Temperature Applications
Title: Ink‐Extrusion 3D Printing and Silicide Coating of HfNbTaTiZr Refractory High‐Entropy Alloy for Extreme Temperature Applications
Abstract An oxygen‐resistant refractory high‐entropy alloy is synthesized in microlattice or bulk form by 3D ink‐extrusion printing, interdiffusion, and silicide coating. Additive manufacturing of equiatomic HfNbTaTiZr is implemented by extruding inks containing hydride powders, de‐binding under H2, and sintering under vacuum. The sequential decomposition of hydride powders (HfH2+NbH+TaH0.5+TiH2+ZrH2) is followed by in situ X‐ray diffraction. Upon sintering at 1400 °C for 18 h, a nearly fully densified, equiatomic HfNbTaTiZr alloy is synthesized; on slow cooling, both α‐HCP and β‐BCC phases are formed, but on quenching, a metastable single β‐BCC phase is obtained. Printed and sintered HfNbTaTiZr alloys with ≈1 wt.% O shows excellent mechanical properties at high temperatures. Oxidation resistance is achieved by silicide coating via pack cementation. A small‐size lattice‐core sandwich is fabricated and tested with high‐temperature flames to demonstrate the versatility of this sequential approach (printing, sintering, and siliconizing) for high‐temperature, high‐stress applications of refractory high‐entropy alloys.  more » « less
Award ID(s):
2004769
PAR ID:
10641385
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Science
Volume:
11
Issue:
17
ISSN:
2198-3844
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Journal of Phase Equilibria and Diffusion)
    null (Ed.)
    The cluster expansion formalism for alloys is used to construct surrogate models for three refractory high-entropy alloys (NbTiVZr, HfNbTaTiZr, and AlHfNbTaTiZr). These cluster expansion models are then used along with Monte Carlo methods and thermodynamic integration to calculate the configurational entropy of these refractory high-entropy alloys as a function of temperature. Many solid solution alloy design guidelines are based on the ideal entropy of mixing, which increases monotonically with N, the number of elements in the alloy. However, our results show that at low temperatures, the configurational entropy of these materials is largely independent of N, and the assumption described above only holds in the high-temperature limit. This suggests that alloy design guidelines based on the ideal entropy of mixing require further examination. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Nature Communications)
    Abstract Energy efficiency is motivating the search for new high-temperature (high-T) metals. Some new body-centered-cubic (BCC) random multicomponent “high-entropy alloys (HEAs)” based on refractory elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known. Here we show, using integrated in-situ neutron-diffraction (ND), high-resolution transmission electron microscopy (HRTEM), and recent theory, that the high strength and strength retention of a NbTaTiV alloy and a high-strength/low-density CrMoNbV alloy are attributable to edge dislocations. This finding is surprising because plastic flows in BCC elemental metals and dilute alloys are generally controlled by screw dislocations. We use the insight and theory to perform a computationally-guided search over 10 7 BCC HEAs and identify over 10 6 possible ultra-strong high-T alloy compositions for future exploration. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Communications Materials)
    Abstract Laser powder-bed fusion (L-PBF) additive manufacturing presents ample opportunities to produce net-shape parts. The complex laser-powder interactions result in high cooling rates that often lead to unique microstructures and excellent mechanical properties. Refractory high-entropy alloys show great potential for high-temperature applications but are notoriously difficult to process by additive processes due to their sensitivity to cracking and defects, such as un-melted powders and keyholes. Here, we present a method based on a normalized model-based processing diagram to achieve a nearly defect-free TiZrNbTa alloy via in-situ alloying of elemental powders during L-PBF. Compared to its as-cast counterpart, the as-printed TiZrNbTa exhibits comparable mechanical properties but with enhanced elastic isotropy. This method has good potential for other refractory alloy systems based on in-situ alloying of elemental powders, thereby creating new opportunities to rapidly expand the collection of processable refractory materials via L-PBF. 
    more » « less
  4. ; ; (, Metals)
    High-entropy alloys (HEAs) prefer to form single-phase solid solutions (body-centered cubic (BCC), face-centered cubic (FCC), or hexagonal closed-packed (HCP)) due to their high mixing entropy. In this paper, we systematically review the mechanical behaviors and properties (such as oxidation and corrosion) of BCC-structured HEAs. The mechanical properties at room temperature and high temperatures of samples prepared by different processes (including vacuum arc-melting, powder sintering and additive manufacturing) are compared, and the effect of alloying on the mechanical properties is analyzed. In addition, the effects of HEA preparation and compositional regulation on corrosion resistance, and the application of high-throughput techniques in the field of HEAs, are discussed. To conclude, alloy development for BCC-structured HEAs is summarized. 
    more » « less
  5. ; ; (, Acta materialia)
    null (Ed.)
    Refractory multi-element alloys (RMEA) with body-centered cubic (bcc) structure have been the object of much research over the last decade due to their high potential as candidate materials for high- temperature applications. Most of these alloys display a remarkable strength at high temperatures, which cannot be explained by the standard model of bcc plasticity based on thermally-activated screw disloca- tion motion. Several works have pointed to chemical energy fluctuations as an essential aspect of RMEA strength that is not captured by standard models. In this work, we quantify the contribution of screw dis- locations to the strength of equiatomic Nb-Ta-V alloys using a kinetic Monte Carlo model fitted to solu- tion energetics obtained from atomistic calculations. In agreement with molecular dynamics simulations, we find that chemical energy fluctuations along the dislocation line lead to measurable concentrations of kinks in equilibrium in a wide temperature range. A fraction of these form cross-kink configurations, which are ultimately found to control screw dislocation motion and material strength. Our simulations (i) confirm that the evolution of cross kinks and self-pinning are strong contributors to the so-called ‘cocktail’ effect in this alloy at low temperature, and (ii) substantiate the notion that screw dislocation plasticity alone cannot explain the high temperature strength of bcc RMEA. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email