TY - JOUR
T1 - Atomic-scale dissecting the formation mechanism of gradient nanostructured layer on Mg alloy processed by a novel high-speed machining technique
AU - Fu, Hui
AU - Zhou, Xiaoye
AU - Wu, Bo
AU - Qian, Lei
AU - Yang, Xu Sheng
N1 - Funding Information:
This work was financially supported by the National Natural Science Foundation of China (Nos. 51701171 and 51971187 ) and the Partner State Key Laboratories in Hong Kong from the Innovation and Technology Commission (ITC) of the Government of the Hong Kong Special Administration Region (HKASR), China . The authors would also like to express their sincere thanks to the financial support from the PolyU Research Office (Project Code: 1-BBXA).
Publisher Copyright:
© 2021
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/8/20
Y1 - 2021/8/20
N2 - Severe plastic deformation (SPD)-induced gradient nanostructured (GNS) metallic materials exhibit superior mechanical performance, especially the high strength and good ductility. In this study, a novel high-speed machining SPD technique, namely single point diamond turning (SPDT), was developed to produce effectively the GNS layer on the hexagonal close-packed (HCP) structural Mg alloy. The high-resolution transmission electron microscopy observations and atomistic molecular dynamics simulations were mainly performed to atomic-scale dissect the grain refinement process and corresponding plastic deformation mechanisms of the GNS layer. It was found that the grain refinement process for the formation of the GNS Mg alloy layer consists of elongated coarse grains, lamellar fine grains with deformation-induced-tension twins and contraction twins, ultrafine grains, and nanograins with the grain size of ∼70 nm along the direction from the inner matrix to surface. Specifically, experiment results and atomistic simulations reveal that these deformation twins are formed by gliding twinning partial dislocations that are dissociated from the lattice dislocations piled up at grain boundaries. The corresponding deformation mechanisms were evidenced to transit from the deformation twinning to dislocation slip when the grain size was below 2.45 μm. Moreover, the Hall-Petch relationship plot and the surface equivalent stress along the gradient direction estimated by finite element analysis for the SPDT process were incorporated to quantitatively elucidate the transition of deformation mechanisms during the grain refinement process. Our findings have implications for the development of the facile SPD technique to construct high strength-ductility heterogeneous GNS metals, especially for the HCP metals.
AB - Severe plastic deformation (SPD)-induced gradient nanostructured (GNS) metallic materials exhibit superior mechanical performance, especially the high strength and good ductility. In this study, a novel high-speed machining SPD technique, namely single point diamond turning (SPDT), was developed to produce effectively the GNS layer on the hexagonal close-packed (HCP) structural Mg alloy. The high-resolution transmission electron microscopy observations and atomistic molecular dynamics simulations were mainly performed to atomic-scale dissect the grain refinement process and corresponding plastic deformation mechanisms of the GNS layer. It was found that the grain refinement process for the formation of the GNS Mg alloy layer consists of elongated coarse grains, lamellar fine grains with deformation-induced-tension twins and contraction twins, ultrafine grains, and nanograins with the grain size of ∼70 nm along the direction from the inner matrix to surface. Specifically, experiment results and atomistic simulations reveal that these deformation twins are formed by gliding twinning partial dislocations that are dissociated from the lattice dislocations piled up at grain boundaries. The corresponding deformation mechanisms were evidenced to transit from the deformation twinning to dislocation slip when the grain size was below 2.45 μm. Moreover, the Hall-Petch relationship plot and the surface equivalent stress along the gradient direction estimated by finite element analysis for the SPDT process were incorporated to quantitatively elucidate the transition of deformation mechanisms during the grain refinement process. Our findings have implications for the development of the facile SPD technique to construct high strength-ductility heterogeneous GNS metals, especially for the HCP metals.
KW - Deformation twinning
KW - Gradient nanostructured Mg alloy
KW - Hall-Petch relationship
KW - High-resolution transition electron microscopy
KW - High-speed machining
UR - http://www.scopus.com/inward/record.url?scp=85100374439&partnerID=8YFLogxK
U2 - 10.1016/j.jmst.2020.10.086
DO - 10.1016/j.jmst.2020.10.086
M3 - Journal article
AN - SCOPUS:85100374439
SN - 1005-0302
VL - 82
SP - 227
EP - 238
JO - Journal of Materials Science and Technology
JF - Journal of Materials Science and Technology
ER -