The Role of Carbon in Grain Refinement of Cast CrFeCoNi High-Entropy Alloys
- PDF / 2,592,288 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 80 Downloads / 245 Views
ODUCTION
HIGH-ENTROPY alloys (HEAs), also referred to multicomponent alloys or compositionally complex alloys, have attracted extensive attention during the past decade due to their unique properties.[1] As proposed firstly by Yeh,[2] HEA is defined as an alloy containing at least five principal elements, each with an atomic percentage between 5 and 35 pct. This definition is extended to the equiatomic quaternary alloys[3–6] with FCC or BCC structure afterwards, since they also have high mixing entropy, and even higher than some non-equiatomic quinary HEAs.[7–9] Therefore, we also
X.W. LIU, W.M. JIANG, Z.T. FAN, L. LIU, D.H. LU, and J.Q. YAO are with the State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan, China and also with the State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, China. G. LIU is with the School of Material Science and Engineering, Xi’an University of Technology, Xi’an 710048, China. X.X. WU is with the Institute for Materials, Ruhr University Bochum, 44801 Bochum, Germany. W.B. ZHANG is with the Institute for Applied Materials—Applied Materials Physics, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany. Contact e-mails: [email protected] and [email protected] Manuscript submitted October 17, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
use this generalized category in the present work. Among these alloys, face-centered cubic (FCC)-based HEAs, especially CrFeCoNi family alloys, were investigated systematically and shown exceptional room temperature and cryogenic mechanical properties.[10–27] Meanwhile, another unique characteristic of HEAs is the absence of ‘‘solvent’’ and ‘‘solute’’ atoms, resulting in a breakdown of the traditional textbook theory that the solutes redistribute during solidification. Therefore, they have more different solidification behaviors compared with the traditional compositionally simple alloys. Casting is a very important technique for almost all the engineering materials to form extremely complicated and thin components. However, the other techniques, such as machining and forging, are only suitable for the relatively simple-shaped components. Even for some FCC alloys with good ductility, e.g., Cu and Al alloys, cast alloys are still required in many cases. Therefore, the casting technique for the above-mentioned FCC HEAs is of importance for applications. In the fields of cast alloys, microstructure control and grain refinement are two of the most importance issues, since the general cast alloys are inclined to grow along the heat flow direction and form bulky columnar gains. These coarse columnar grains lead to two typical shortcomings. Firstly, these grains are generally very coarse with hundreds of micrometers thickness or more. For
example, some cast Al alloys could form columnar grains with the thickness of more than 1 mm.[28] This type of coarse columnar grains also occurs in the as-cast microstructure of HEAs, e.g., as-c
Data Loading...
