TY - JOUR
T1 - Grain boundary segregation behavior in Fe-rich Sm-Co-Fe-Cu-Zr magnets
AU - Jia, Wentao
AU - Liu, Yao
AU - Yuan, Tao
AU - Wang, Fang
AU - Chen, Yanan
AU - Ma, Tianyu
N1 - Publisher Copyright:
© 2022
PY - 2022/5
Y1 - 2022/5
N2 - Grain boundary (GB) deficiencies, including magnetically softer phase and precipitate-free-zones (PFZs), have been recognized as important microstructural origins for the lower-than-ideal energy product of precipitate-hardening Sm-Co-Fe-Cu-Zr magnets with high Fe content. However, the underlying co-aggregations or co-depletions of the interactive compositional variables and their effect on the heterogeneous precipitation near GBs are still unclear, being one of the key issues to optimize the microstructure towards high magnetic performance. Herein, the GB metallurgical segregation behavior during decomposition process of a commercially sintered magnet Sm25Co42.9Fe23.5Cu5.6Zr3.0 (wt.%) was systematically investigated. The concurrently-happened co-aggregations of Sm/Zr/Cu and co-depletions of Co/Fe near GBs lead to further growth and new formation of Zr-stabilized Smn+1Co5n-1-type (n = 2 for 1:3R, n = 3 for 2:7R, n = 4 for 5:19R) sheet-like precipitates, which in turn strongly affect the precipitation behavior surrounding them. The further growth of primary Smn+1Co5n-1 sheet-like precipitates leads to misaligned Sm-rich PFZs (without 1:5H and 1:3R precipitates that are normally formed within grain interiors), while the formation of secondary Smn+1Co5n-1 sheet-like precipitates leads to Sm-lean PFZs, characterized by misaligned regions without 1:5H and 1:3R precipitates or coherent band-like regions without 1:5H precipitates. Further magnetic domain studies and magnetic measurements revealed that the GB segregation-induced Smn+1Co5n-1 soft phases and misaligned PFZs not only reduce the efficient domain wall pinning sites but also weaken the [001] grain texture, being detrimental to both coercivity and remanence. To achieve high magnetic performance, the processing condition should be carefully controlled to balance the competitive contributions between the segregation-induced GB deficiencies and the normal cellular nanostructure within grain interiors.
AB - Grain boundary (GB) deficiencies, including magnetically softer phase and precipitate-free-zones (PFZs), have been recognized as important microstructural origins for the lower-than-ideal energy product of precipitate-hardening Sm-Co-Fe-Cu-Zr magnets with high Fe content. However, the underlying co-aggregations or co-depletions of the interactive compositional variables and their effect on the heterogeneous precipitation near GBs are still unclear, being one of the key issues to optimize the microstructure towards high magnetic performance. Herein, the GB metallurgical segregation behavior during decomposition process of a commercially sintered magnet Sm25Co42.9Fe23.5Cu5.6Zr3.0 (wt.%) was systematically investigated. The concurrently-happened co-aggregations of Sm/Zr/Cu and co-depletions of Co/Fe near GBs lead to further growth and new formation of Zr-stabilized Smn+1Co5n-1-type (n = 2 for 1:3R, n = 3 for 2:7R, n = 4 for 5:19R) sheet-like precipitates, which in turn strongly affect the precipitation behavior surrounding them. The further growth of primary Smn+1Co5n-1 sheet-like precipitates leads to misaligned Sm-rich PFZs (without 1:5H and 1:3R precipitates that are normally formed within grain interiors), while the formation of secondary Smn+1Co5n-1 sheet-like precipitates leads to Sm-lean PFZs, characterized by misaligned regions without 1:5H and 1:3R precipitates or coherent band-like regions without 1:5H precipitates. Further magnetic domain studies and magnetic measurements revealed that the GB segregation-induced Smn+1Co5n-1 soft phases and misaligned PFZs not only reduce the efficient domain wall pinning sites but also weaken the [001] grain texture, being detrimental to both coercivity and remanence. To achieve high magnetic performance, the processing condition should be carefully controlled to balance the competitive contributions between the segregation-induced GB deficiencies and the normal cellular nanostructure within grain interiors.
KW - Grain boundary segregation
KW - Magnetic properties
KW - Permanent magnets
KW - Sm-Co magnets
UR - https://www.scopus.com/pages/publications/85125904197
U2 - 10.1016/j.mtla.2022.101382
DO - 10.1016/j.mtla.2022.101382
M3 - 文章
AN - SCOPUS:85125904197
SN - 2589-1529
VL - 22
JO - Materialia
JF - Materialia
M1 - 101382
ER -