TY - JOUR
T1 - Probing deformation mechanisms of a FeCoCrNi high-entropy alloy at 293 and 77 K using in situ neutron diffraction
AU - Wang, Yiqiang
AU - Liu, Bin
AU - Yan, Kun
AU - Wang, Minshi
AU - Kabra, Saurabh
AU - Chiu, Yu-Lung
AU - Dye, David
AU - Lee, Peter D.
AU - Liu, Yong
AU - Cai, Biao
PY - 2018/8/1
Y1 - 2018/8/1
N2 - The deformation responses at 77 and 293 K of a FeCoNiCr high-entropy alloy, produced by a powder metallurgy route, are investigated using in situ neutron diffraction and correlative transmission electron microscopy. The strength and ductility of the alloy are significant improved at cryogenic temperatures. The true ultimate tensile strength and total elongation increased from 980 MPa and 45% at 293 K to 1725 MPa and 55% at 77K, respectively. The evolutions of lattice strain, stacking fault probability, and dislocation density were determined via quantifying the in situ neutron diffraction measurements. The results demonstrate that the alloy has a much higher tendency to form stacking faults and mechanical twins as the deformation temperature drops, which is due to the decrease of stacking fault energy (estimated to be 32.5 mJ/m2 and 13 mJ/m2 at 293 and 77 K, respectively). The increased volume faction of nano-twins and twin-twin intersections, formed during cryogenic temperature deformation, has been confirmed by transmission electron microscopy analysis. The enhanced strength and ductility at cryogenic temperatures can be attributed to the increased density of dislocations and nano-twins. The findings provide a fundamental understanding of underlying governing mechanistic mechanisms for the twinning induced plasticity in high entropy alloys, paving the way for the development of new alloys with superb resistance to cryogenic environments.
AB - The deformation responses at 77 and 293 K of a FeCoNiCr high-entropy alloy, produced by a powder metallurgy route, are investigated using in situ neutron diffraction and correlative transmission electron microscopy. The strength and ductility of the alloy are significant improved at cryogenic temperatures. The true ultimate tensile strength and total elongation increased from 980 MPa and 45% at 293 K to 1725 MPa and 55% at 77K, respectively. The evolutions of lattice strain, stacking fault probability, and dislocation density were determined via quantifying the in situ neutron diffraction measurements. The results demonstrate that the alloy has a much higher tendency to form stacking faults and mechanical twins as the deformation temperature drops, which is due to the decrease of stacking fault energy (estimated to be 32.5 mJ/m2 and 13 mJ/m2 at 293 and 77 K, respectively). The increased volume faction of nano-twins and twin-twin intersections, formed during cryogenic temperature deformation, has been confirmed by transmission electron microscopy analysis. The enhanced strength and ductility at cryogenic temperatures can be attributed to the increased density of dislocations and nano-twins. The findings provide a fundamental understanding of underlying governing mechanistic mechanisms for the twinning induced plasticity in high entropy alloys, paving the way for the development of new alloys with superb resistance to cryogenic environments.
KW - high entropy alloy
KW - deformation twinning
KW - neutron diffraction
KW - cryogenic deformation
KW - stacking fault energy
U2 - 10.1016/j.actamat.2018.05.013
DO - 10.1016/j.actamat.2018.05.013
M3 - Article
SN - 1359-6454
VL - 154
SP - 79
EP - 89
JO - Acta Materialia
JF - Acta Materialia
ER -