Microstructure and mechanical properties of the new Nb25Sc25Ti25Zr25 eutectic high entropy alloy

The novel quaternary Nb25Sc25Ti25Zr25 (at.%) high entropy alloy with dual-phase structure was developed and cast by arc melting of elemental precursors. The as-cast state comprised of lamellar eutectics with alternating α(Sc, Zr) with HCP lattice plates having thickness of 30–50nm, length up to 600n...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2016-01, Vol.651, p.590-597
Main Authors: Rogal, Ł., Morgiel, J., Świątek, Z., Czerwiński, F.
Format: Article
Language:English
Subjects:
Annealing
Compressive strength
Entropy
Eutectic composition
Eutectics
High entropy alloys
Lamellar structure
Microstructure
Nb25Sc25Ti25Zr25 alloy
Plates
TEM
Zirconium
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Summary:The novel quaternary Nb25Sc25Ti25Zr25 (at.%) high entropy alloy with dual-phase structure was developed and cast by arc melting of elemental precursors. The as-cast state comprised of lamellar eutectics with alternating α(Sc, Zr) with HCP lattice plates having thickness of 30–50nm, length up to 600nm and inter-lamellar spacing of 5–40nm, embedded in the β-NbZrTi matrix with BCC structure. While the α(Sc, Zr) plates showed reduced content of Nb, the β-NbZrTi matrix was particularly depleted in Sc. The unique mixture of fine hexagonal α(Sc, Zr) plates within the β-NbTiZr matrix in as-cast state led to relatively high combination of strength and ductility: the alloy with initial hardness of 418 HV reached compressive strength of 1250MPa, yield strength of 1020MPa and compressibility of 8.2%. The phase composition exhibited high stability with no significant changes taking place after annealing at 1000˚C for 24h. The high-temperature exposure caused only coarsening of α(Sc, Zr) hexagonal plates, which reached 3μm in width and 5-10μm in length. The plastic strain of the annealed alloy with hardness of 202 HV increased to 20% while compression strength decreased to 670MPa. As opposed to the as-cast state, the annealed alloy exhibited limited strain hardening during room-temperature compression.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2015.10.071