Temperature-dependent tensile behavior of the HfNbTaTiZr multi-principal element alloy

Ink‐Extrusion 3D Printing and Silicide Coating of HfNbTaTiZr Refractory High‐Entropy Alloy for Extreme Temperature Applications

“…Arc‐melted equiatomic HfNbTaTiZr is well known to display a metastable single β‐BCC phase, which is the microstructure that has been so far studied and tested in the literature. [ 23 , 25 , 43 ] However, a multiphase (β‐BCC1 + β‐BCC2 + α‐HCP) microstructure is obtained in our specimens, after a very different processing route, i.e., sintering at 1400 °C for 18 h followed by slow cooling (5 °C min −1 ). To understand the reason for the formation of the current microstructure, a 1 h homogenization at 1500 °C followed by water quenching is performed to simulate the cooling rate of arc melting.…”

“…The stress drop after yielding at 1000 °C shown in Figure 4a may be due to dynamic recovery and recrystallization which were reported previously for arc melted HfNbTaTiZr. [ 23 , 25 ] In addition, cracks forming along shearing bands, observed on the heavily deformed sample (inset in Figure 4a ), may also have contributed to the softening of the flow stress.…”

“…We are not aware of any published work on 3D ink-extrusion printing of RHEA, except for Zhao et al who used 3D ink-extrusion printing to fabricate equiatomic NbTaTiZr scaffolds, which showed good biocompatibility and met the requirements for orthopedic implants. [21] In the cast state, equiatomic HfNbTaTiZr shows good tensile ductility at room temperature (8-16% [22][23] ) and excellent strength at high temperatures [24] (e.g., yield strength of 163-530 MPa at 1000 °C for strain rates of 10 −4 -10 −2 s −1 ). [25] However, the poor oxygen resistance of HfNbTaTiZr prevents most practical applications at high temperatures.…”

“…In the cast state, equiatomic HfNbTaTiZr shows good tensile ductility at room temperature (8–16% [ 22 , 23 ] ) and excellent strength at high temperatures [ 24 ] (e.g., yield strength of 163–530 MPa at 1000 °C for strain rates of 10 −4 –10 −2 s −1 ). [ 25 ] However, the poor oxygen resistance of HfNbTaTiZr prevents most practical applications at high temperatures.…”

Kink bands promote exceptional fracture resistance in a NbTaTiHf refractory medium-entropy alloy

“…On the opposite end of this spectrum, the group IV and V mixtures, particularly the model HfNbTaTiZr alloy, can exhibit substantial tensile plasticity and even high ambient temperature fracture toughness (10). However, these systems do not possess adequate thermodynamic phase stability, which is detrimental to their high-temperature mechanical properties (11)(12)(13)(14).…”