Magnetic properties of spray-formed Fe–6.5%Si and Fe–6.5%Si–1.0%Al after rolling and heat treatment
Magnetic properties of spray-formed Fe–6.5%Si and Fe–6.5%Si–1.0%Al after rolling and heat treatment
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DOI：
10.1016/j.jmmm.2008.04.104
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发表时间：
2008-10
影响因子：
2.7
通讯作者：
C. Bolfarini;M. Silva;A. Jorge;C. S. Kiminami;W. Botta
中科院分区：
文献类型：
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作者：
C. Bolfarini;M. Silva;A. Jorge;C. S. Kiminami;W. Botta
商业Fe-Si钢中的最大硅含量被限制为约3.5wt%Si，因为当超过该最大值时延展性急剧下降，阻碍了通过冷/热轧生产薄板。然而，在约6.5wt%Si下获得最佳磁性能，该硅含量使得磁致伸缩几乎为零并且使磁损耗最小化。我们的研究小组使用喷射成形技术，通过仔细控制工艺和后续轧制操作的诸多变量，成功地生产出了这种高硅合金薄板。本文研究了喷射成形Fe-6.5wt%Si和Fe-6.5wt%Si-1.0wt%Al合金经温轧和热处理后的磁性能和显微组织。Fe-6.5wt%Si合金脆性的主要原因是B_2相的长程有序化导致了过早断裂。铝的存在可以避免B2的形成，提高合金的塑性。Fe-6.5wt%Si二元合金的磁性能最好，这归因于其再结晶后的粗晶粒尺寸（≤ 500μm;含Al合金为340μm）。TEM分析表明，热处理后，在较低的冷却速率下，合金中形成了尺寸约为50- 300 nm的B2畴结构。这种结构有助于进一步提高磁性能，但其效果不如晶粒尺寸那么强。Al的添加到二元合金抑制B2的形成，如穆斯堡尔谱所示，显然阻碍了过度的晶粒生长，这可以解释与二元合金相比，磁性能稍差。
The maximum silicon content in commercial Fe–Si steels is limited to about 3.5wt%Si, since the ductility declines sharply as this maximum is exceeded, hindering the production of thin sheets by cold/hot rolling. However, the best magnetic properties are attained at about 6.5wt%Si, a silicon content that renders magnetostriction practically null and minimizes magnetic losses. Using spray-forming, our research group has successfully produced this type of high silicon alloy in thin sheet form by carefully controlling the many variables of the process and subsequent rolling operations. In the present study, we investigated the magnetic properties and the microstructure of spray-formed Fe–6.5wt%Si and Fe–6.5wt%Si–1.0wt%Al alloys after warm rolling and heat treatment. The main cause for the brittleness of Fe–6.5wt%Si alloy has been attributed to the B2 phase long-range ordering, which leads to premature fractures. The presence of aluminum could avoid B2 formation and improve the alloy's ductility. The binary Fe–6.5wt% Si alloy showed the best magnetic properties, which were ascribed to a recrystallized, coarse grain size (∼500μm; and 340μm for the Al-containing alloy). TEM analysis showed that a well-developed B2 domain structure (about 50–300nm in size) was formed in the binary alloy when low cooling rates are prevailing after heat treatment. This structure contributed to improve additionally the magnetic properties, but its effect was not so strong as that of the grain size. The addition of Al to the binary alloy suppressed B2 formation, as indicated by Mossbauer spectroscopy, and apparently hindered excessive grain growth, which may explain the slightly poorer magnetic properties when compared with the binary alloy.