首页|Polymorphic transformation and elemental diffusional controlled phase spheroidization of eutectic VNbTiSi medium entropy alloy during heat treatment
Polymorphic transformation and elemental diffusional controlled phase spheroidization of eutectic VNbTiSi medium entropy alloy during heat treatment
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NSTL
Elsevier
Microstructure evolution of a eutectic VNbTiSi medium entropy alloy (MEA) was systematically investigated during annealing heat treatment. Polymorphic transformation from beta-(Nb, X)(5)Si-3, a high-temperature metastable phase, to '-or gamma-(Nb, X)(5)Si(3 )is revealed and is demonstrated to be closely related to element diffusion. There was mutual diffusion between V and Si, forming a diffusion transition, and the Ti diffusion promoted the formation of gamma-(Nb, X)(5)Si-3 mainly distributed at the grain boundary because of the Ti su-persaturation in the BCC phase during solidification. Strong elemental diffusion promotes the formation of a thermal groove at the three junctions of sub-grain boundaries, contributing to the fast spheroidization of (Nb, X)(5)Si-3, while the termination migration dominates the subsequent coarsening stage. Polymorphic transformation of silicides brings in sub-grain boundaries or low angle grain boundaries (LAGBs), con-tributing to silicide refinement. As a result, the compressive strength at elevated temperatures is greatly improved due to the increasing volume fraction of (Nb, X)(5)Si-3 after heat treatment. (C) 2022 Elsevier B.V. All rights reserved.
NSTL
Elsevier
