Stabilization of nanocrystalline alloys at high temperatures via utilizing high-entropy grain boundary complexions

In this study, the effects of the addition of Mg to the grain growth of austenite and the magnesium-based inclusions to mobility were investigated in SS400 steel at high temperatures. A high-temperature confocal scanning laser microscope (HT-CSLM) was employed to directly observe, in situ, the grain structure of austenite under 25 torr Ar at high temperatures. The grain size distribution of austenite showed the log-normal distribution. The results of the grain growth curves using 3D surface fitting showed that the n and Q values of the growth equation parameters ranged from 0.2 to 0.26 and from 405 kJ/mole to 752 kJ/mole, respectively, when adding 5.6–22 ppm of Mg. Increasing the temperature from 1150 to 1250 °C for 20 min and increasing the addition of Mg by 5.6, 11, and 22 ppm resulted in increases in the grain boundary velocity. The effects of solute drag and Zener pinning on grain boundary mobility were also calculated in this study.

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Plastic deformation mechanisms of equiatomic Ni20Ti20Fe20Al20Cu20 high-entropy alloy at high temperatures

Journal of Materials Science ◽

10.1007/s10853-016-0609-x ◽

2016 ◽

Vol 52 (6) ◽

pp. 3199-3207 ◽

Cited By ~ 8

Author(s):

Shuyong Jiang ◽

Dong sun ◽

Yanqiu Zhang ◽

Sibing Wang ◽

Chengzhi Zhao

Keyword(s):

Plastic Deformation ◽

High Temperatures ◽

Deformation Mechanisms ◽

High Entropy Alloy ◽

High Entropy

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Infrared Brazing of CoCrFeMnNi Equiatomic High Entropy Alloy Using Nickel-Based Braze Alloys

Entropy ◽

10.3390/e21030283 ◽

2019 ◽

Vol 21 (3) ◽

pp. 283 ◽

Cited By ~ 4

Author(s):

Chieh Lin ◽

Ren-Kae Shiue ◽

Shyi-Kaan Wu ◽

Huai-Li Huang

Keyword(s):

Shear Strength ◽

Grain Boundary ◽

High Entropy Alloy ◽

Solidification Shrinkage ◽

Vacuum Brazing ◽

High Entropy ◽

Average Shear Strength ◽

Average Shear ◽

Brazed Joints ◽

Liquidus Temperatures

Infrared vacuum brazing of CoCrFeMnNi high entropy alloy (HEA) using BNi-2 and MBF601 fillers has been investigated. Both brazes show poor wettability at temperatures only 20 °C above their liquidus temperatures. However, the wettability of BNi-2 and MBF601 fillers on CoCrFeMnNi HEA is greatly improved with increasing the test temperatures, 50 °C above their liquidus temperatures. The BNi-2 brazed joints are dominated by Ni-rich matrix with huge CrB and a few tiny boride precipitates. Average shear strengths of joints increase with increasing brazing temperature and/or time, and fracture location changes from blocky CrB in the brazed zone to grain boundary boride in the substrate. The MBF601 brazed joints are composed of CoCrFeMnNi-based matrix, particles of B/Co/Cr/Fe/Mn/Ni/P compounds, and some phosphides form along the grain boundaries of the substrate. The specimen brazed with MBF601 filler foil at 1050 °C for 600 s has the highest average shear strength of 321 MPa, while that brazed at 1080 °C for 600 s has a lower average shear strength of 271 MPa due to the presence of solidification shrinkage voids.

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