EN17.03.11 : Pressure-Induced Phase Modifications in Al-Based High-Entropy Alloys AlxCoCrFeNi (x=0.1, 0.3, 0.75, 1.5)

5:00 PM–7:00 PM Apr 3, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Chenxu Wang1 Cameron Tracy1 Sulgiye Park1 Chien-Hung Chen1 Tengfei Yang2 Congyi Li2 Yugang Wang3 Yong Zhang5 Wendy Mao1 4 Rodney Ewing1

1, Stanford University, Stanford, California, United States
2, University of Tennessee, Knoxville, Knoxville, Tennessee, United States
3, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology, Beijing, , China
5, University of Science and Technology Beijing, Beijing, , China
4, SLAC National Accelerator Laboratory, Menlo Park, California, United States

Pressure-induced structural modifications in high-entropy alloys with varying Al content, AlxCoCrFeNi (x=0.1, 0.3, 0.75, 1.5), have been investigated at pressures up to ~50 GPa by synchrotron X-ray diffraction and transmission electron microscopy (TEM). In AlxCoCrFeNi compounds with x≧0.3, all of which exhibit initial pure fcc structures, the proportionality between the Al content and the transformation pressure is observed. This is attributed to the large size of Al atoms relative to those of the other constituent elements, which leads to more structural distortion in Al0.3CoCrFeNi and subsequently an increase in the formation energy of the stacking faults. High-resolution TEM results show the variation of the stacking sequence from ABCABC (fcc) to ABABAB (hcp) in Al0.1CoCrFeNi following exposure to high pressure. In Al0.75CoCrFeNi, which exhibits an initial dual-phase structure, the result again shows the transformation to an hcp phase despite its higher Al content, which might be due to the presence of the bcc phase that is more amenable to the pressure-induced phase modification. However, the trend of transformation inhibition by increasing Al content is again observed, with Al1.5CoCrFeNi retaining its initial structures up to the highest pressure achieved.