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November 13-15, 2017 | Las Vegas, USA
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th
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RRJOMS | Volume 5 | Issue 7 | November, 2017
Age heat treatments of the CoCrFeNiTi
0.3
high-entropy alloy
Tao-Tsung Shun, Cheng-Ying Hsieh, Wei-Jhe Hung
and
Che-Fu Lee
Feng Chia University, Taiwan
U
nlike traditional alloys constituted by one or two principal elements, the high-entropy alloys are constructed by at least multi-
principal elements, each with concentrations between 5 at.% and 35 at.%. These alloys exhibit good wear resistance, thermal
stability, and high-temperature compressive strength, which render them promising for use as tools, molds, die, and furnace parts.
Previously, we proposed that the CoCrFeNiTi
0.3
high-entropy alloy was promising for the development of a ductile, high-strength
alloy owing to its high compressive stress of 1529 MPa and good fracture strain of 0.60. To further understand microstructure
evolution as well as the age-hardening phenomena of this alloy, the effects of age heat treatments for 24-144 h at 500-1000
0
C on
the hardness and microstructure of as-cast CoCrFeNiTi
0.3
high-entropy alloy were reported in this paper. The results showed that
the as-cast alloy displayed a dendritic structure which dendrite was a Ti-lean face-centered cubic solid solution phase (FCC1) and
interdendrite consisted of three phases including a Ti-rich face-centered cubic solid solution phase (FCC2) and a mixture of (Ni,Ti)-
rich h phase and (Cr,Fe)-rich s phase. After 144 h aging treatment, age-hardening was apparently observed at temperature of 600-800
0
C due to the transformation of FCC2 phase to h+s phases. The optimum hardness was obtained at an aging temperature of 700
0
C
which made the hardness increase from HV366 to HV508. However, age-softening occurred at 900-1000
0
C due to the dissolution of
h+s phases. The s phase completely dissolved into FCC1 matrix at 1000
0
C which brought the alloy hardness to the minimum HV223.
Biography
Tao-Tsung Shun received PhD degrees from University of Utah in Metallurgical Engineering at the age of 30 years. He had worked as a senior engineer for 3 years and a
researcher for 10 years in Walsin Lihwa Stainless steel Co. and Industrial Technology Research Institute, respectively. Currently, he is an associate professor in the De-
partment of Materials Science and Engineering, Feng Chia University, Taiwan. His present research interests are in developing ductile, high strength high-entropy alloys.
ttshun@fcu.edu.twTao-Tsung Shun et al., Res. Rev. J Mat. Sci. 2017, 5:7
DOI: 10.4172/2321-6212-C1-012