Role of primary Zr-rich particles on microstructure and magnetic properties of 2∶17-type Sm-Co-Fe-Cu-Zr permanent magnets

• 作者: Tao Yuan Xin Song Xianglong Zhou Wentao Jia Munzali Musa Jingdong Wang Tianyu Ma
• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2020,（18）
• 页码范围: 73-81
• 页数: 9页
• 语种: 英文

摘要

Trace Zr addition is essential for achieving desired cellular nanostructure and large coercivity in the pinning-controlled 2∶17-type Sm-Co-Fe-Cu-Zr magnets that have served as the strongest high temper-ature permanent magnets for over 40 years.However,accompanying this is the formation of Zr-rich particles that may deteriorate the hard magnetic properties.Besides the formerly-reported 1∶3R Zr-rich platelets,in this work,1-2 μm sized Zr6(Co,Fe)23 (6∶23) particles (Fm (3) m) and 100-200 nm sized 1∶3R Zr-rich particles were also found based on combined structural identifications and element mapping analysis.Around such particles,the desired 1 ∶5H cell wall precipitates that provide the strongest pinning force of magnetic domain wall motions are rare,forming the precipitate-free-zones (PFZs).The 1∶5H-PFZs and the soft magnetism of both 6∶23 and 1∶3R Zr-rich particles act as local weak pinning points,which are unfavorable to retain the large magnetization in strong opposite fields and lead to poor squareness.As observed in a Sm25Co45.9Fe19.5Cu5.6Zr4.0 (wt.％) magnet,the co-existence of such Zr-rich particles and the associated 1∶5H-PFZs leads to a pretty low squareness factor of only 52.89 ％ given the large coercivity of 29.04 kOe.Our findings suggest that careful controlling the Zr content and avoiding its aggregation to form harmful 6∶23 and 1∶3R Zr-rich particles are essential for achieving high squareness as well as large energy product in the Sm-Co-Fe-Cu-Zr permanent magnets.