Research & Reviews: Journal of Material Sciences
MenuISSN:2321-6212
ISSN:2321-6212
Tao-Tsung Shun, Cheng-Ying Hsieh, Wei-Jhe Hung and Che-Fu Lee
Feng Chia University, Taiwan
Posters & Accepted Abstracts: Res. Rev. J Mat. Sci
Unlike traditional alloys constituted by one or two principal elements, the high-entropy alloys are constructed by at least multiprincipal 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 CoCrFeNiTi0.3 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 500-10000C on the hardness and microstructure of as-cast CoCrFeNiTi0.3 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 0C due to the transformation of FCC2 phase to h+s phases. The optimum hardness was obtained at an aging temperature of 700 0C which made the hardness increase from HV366 to HV508. However, age-softening occurred at 900-10000C due to the dissolution of h+s phases. The s phase completely dissolved into FCC1 matrix at 10000C which brought the alloy hardness to the minimum HV223.
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 Department of Materials Science and Engineering, Feng Chia University, Taiwan. His present research interests are in developing ductile, high strength high-entropy alloys.