High-entropy Al_0.3CoCrFeNi alloy fibers with high tensile strength and ductility at ambient and cryogenic temperatures

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• 作者：Dongyue Li^a ; Chengxin Li^a ; Tao Feng^b ; Yidong Zhang^b ; Gang Sha^b ; John J. Lewandowski^c ; Peter K. Liaw^d ; Yong Zhang^a ; ^{drzhangy@ustb.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：High-entropy alloy ; Fibers ; Tensile strength and ductility ; Cryogenic behavior ; Nano-twinning
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：15 January 2017
• 年：2017
• 卷：123
• 期：Complete
• 页码：285-294
• 全文大小：4769 K

文摘

High-entropy alloys (HEAs) are multi-component systems based on novel alloy composition designs with entropy maximization. They feature an array of unique mechanical properties when compared with traditional alloys. In this study, HEA fibers with diameters ranging from 1 to 3.15 mm in diameter, with the composition of Al_0.3CoCrFeNi (atomic percent, at.%), were successfully fabricated by hot-drawing, followed by microstructural characterization using scanning-electron microscopy (SEM) and transmission-electron microscopy (TEM). The compositional variations within and between fibers were determined using energy-dispersive X-ray spectroscopy in TEM along with atomic-probe tomography (APT). These analyses revealed a homogeneous face-centered cubic (FCC) structure in the as-cast material, while post processing (e.g., forging and wire drawing) produced nanosized B2 particles in an FCC matrix. Electron back-scatter diffraction (EBSD) was used to determine the evolution of the texture and grain boundary character after processing of the fibers. The tensile strength and plasticity of the fibers were determined at both 298 K (1207 MPa/7.8%) and 77 K (1600 MPa/17.5%). Detailed TEM analyses revealed that the improvement of mechanical properties at 77 K (i.e. increased strength and ductility) is due to a change in deformation mechanisms from the planar slip of dislocations to nano-twinning. Such properties could be beneficial for cryogenic applications.