Microtexture formation of Ni₉₉B₁ alloys solidified on an ESL and an EML—a study based on the EBSP technique

详细信息    查看全文

• 作者：Mingjun Li ; Takehiko Ishikawa ; Kosuke Nagashio ; Kazuhiko Kuribayashi ; Shinichi Yoda
• 关键词：Containerless solidification ; Microstructure ; Electron backscatter diffraction pattern ; Electromagnetic stirring ; Dendrite fragmentation
• 刊名：Materials Science and Engineering: A
• 出版年：2007
• 出版时间：25 March 2007
• 年：2007
• 卷：449-451
• 期：Complete
• 页码：684-688
• 全文大小：1414 K

文摘

We employed an electrostatic levitator (ESL) and an electromagnetic levitator (EML) to solidify Ni₉₉B₁ (at. % ) alloys at various undercoolings. The microstructures and microtextures were revealed by using the electron backscatter diffraction pattern (EBSP) technique in a scanning electron microscope. It is found that that no significant refinement can be identified at the low and medium undercooling regimes for the primary trunk in the sample solidified on the ESL, while the fragmentation of the secondary and even tertiary branches may take place to generate equiaxed grains. Further investigation by the EBSP reveals that neighboring grains have small misorientation angles, which may be ascribed to the absence of mechanical stirring from electromagnetic eddy current. A sharp contrast is that the samples solidified on the EML at low and medium undercoolings have refined equiaxed microstructures. The EBSP mapping reveals that the equiaxed grains yielded on the EML have a random distribution in crystallographic orientations among neighboring grains, indicating that electromagnetic stirring (EMS) induced by the electromagnetic field in the EML plays a vital role in promoting fragmentation and thus generating refined grains and random distribution in orientation. Regarding to the refined microstructure at high undercoolings, no significant difference arises in the samples processed between the EML and ESL.