Effect of Cr Content on Microstructure of Spinodal Decomposition and Properties in FeCrCoSi Permanent Magnet Alloy
Received date: 2021-03-01
Revised date: 2021-06-08
Online published: 2021-06-09
Supported by
National Natural Science Foundation of China(51674083);Programme of Introducing Talents of Discipline Innovation to Universities 2.0(BP0719037);National Science Foundation of America(DMR-1157490)
FeCrCo permanent magnet alloys draw wide attention because of their excellent machinability. These alloys can be deformed and extruded into thin wires or sheets for various applications, such as electric motors, telephone receivers, printers, and stereo cartridges. In these alloys, the content and distribution of Cr play an important role in improving their magnetic and hardness properties. To optimize both properties of these alloys, the effect of Cr must be studied. This study describes the effect of Cr content on microstructure, i.e., volume fraction, size, and composition of α 1 and α 2 phases in (84 - X)FeXCr15Co1Si (X = 20, 25, 30, 35, mass fraction, %) samples using atomic-resolution STEM. The effect of microstructure parameters on both Vickers hardness and magnetic properties was evaluated. STEM images showed that the average size of the α 1 phase increased from 26 nm to 55 nm with an increase in Cr content from 20% to 35%. When the content of Cr increased from 20% to 25%, the volume fraction of the α 1 phase increased by 12%, and when the content of Cr increased beyond 25%, the volume fraction remained the same. EDS results showed that with the increase of Cr content, in the (Fe-Co)-rich α 1 phase, the content of Fe decreased, whereas the contents of Cr and Co increased. By contrast, in the Cr-rich α 2 phase, the contents of Fe and Co decreased but the content of Cr increased. After step aging, hardness increased because of spinodal decomposition and continued to increase with an increase in Cr content. Remanence, coercivity, and magnetic energy product reached their maximum values when the content of Cr was at 25% and decreased as the content of Cr increased. The dependence of magnetic properties on the size, volume fraction, composition of α 1 phase, and difference in composition between α 1 and α 2 phases was discussed. The mechanism for hardening was also discussed, which increased with the Cr content.
Key words： FeCrCoSi alloy; spinodal decomposition; STEM-HAADF; magnetic property; hardness
Zhaolong XIANG , Lin ZHANG , Yan XIN , Bailing AN , Rongmei NIU , Jun LU , Masoud MARDANI , Ke HAN , Engang WANG . Effect of Cr Content on Microstructure of Spinodal Decomposition and Properties in FeCrCoSi Permanent Magnet Alloy[J]. Acta Metall Sin, 2022 , 58(1) : 103 -113 . DOI: 10.11900/0412.1961.2021.00094
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