Open AccessPrecipitation behavior of yttrium-rich nano-phases in AlCoCrFeNi2.1Yx high-entropy alloy
Author(s) -
Minghong Sha,
Yanwen Zhou,
Ning Wang,
Dao-Yin Yu,
Zhongjun Wang,
Xingang Ai,
Hongbin Wang,
Minggang Shen,
Shengli Li
Publication year - 2020
Publication title -
materials research express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 35
ISSN - 2053-1591
DOI - 10.1088/2053-1591/abcf7c
Subject(s) - materials science , yttrium , high entropy alloys , alloy , transmission electron microscopy , phase (matter) , cubic crystal system , precipitation , nano , crystallography , microstructure , differential scanning calorimetry , scanning electron microscope , r phase , lamellar structure , analytical chemistry (journal) , metallurgy , composite material , thermodynamics , nanotechnology , martensite , chemistry , physics , organic chemistry , chromatography , meteorology , oxide
In this paper, rare earth element yttrium (Y) was selected to be doped into AlCoCrFeNi 2.1 Y x ( x = 0, 0.1%, 0.3%, 0.5%, and 1.0%) high-entropy alloy in order to refine grain and increase yielding strength. The precipitation behavior of the Y-rich nano-phases in the face centered cubic (FCC (L1 2 )) phase and the body centered cubic (BCC (B2)) phase was investigated by x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and differential scanning calorimetry. Refined crystal grains were observed due to the high-density precipitation. The nano-phase within the BCC(B2) phase was (Al-Ni-Y)-rich phase and single cubic (SC) structure. The nano-phase formed within the FCC (L1 2 ) phase was (Fe-Co-Cr-Y)-rich phase and FCC structure. Fine (Al-Ni-Y)-rich nano-particles were formed due to the addition of Y and the amount of the nano-phase increased with increasing Y content. The adoption of Y promoted dispersed precipitation of (Al-Ni-Y)-rich nano-phase under deformation. The more Y content, the more nano-precipitates. When Y =1.0 at.%, the lamellar structure was transformed into bamboo-like structure in the BCC phase due to the segregation of Y. Double yielding phenomenon occurred during the compression deformation of the AlCoCrFeNi 2.1 Y x alloys (when x ≥ 0.5 at.%) and caused an increase of yielding strength by 40%. It was since the barrier effect of both the (Al-Ni-Y)-rich nano-precipitation and the (Fe-Co-Cr-Y)-rich nano-phases on the dislocations within grains and grain boundaries led to the second yielding. With the further increase of Y content, the lamellar BCC phase was separated from the bamboo-like BCC phase owing to the super-saturated precipitation and segregation of Y at the solidification front of B2 phase, leading to a degradation of mechanical properties.