Tungsten wires and porous NiAl prepared through directional solidification and selective dissolution |
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Authors: | Zhilong Zhao Jianjun Gao Lufeng Wei Kai Chui |
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Affiliation: | School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an, China |
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Abstract: | The combination of directional solidification and selective dissolution was applied to fabricate tungsten (W) wires and porous NiAl matrix. A NiAl–W pseudobinary eutectic alloy with 1.5?at.% tungsten was directionally solidified in a Bridgman-type oven at 1700°C. Results confirmed that the relationships of the growth rate with the interfibrous spacing and diameter of W fibrous phases in the directionally solidified samples are in accordance with the Jackson and Hunt (J?H) model. Afterward, the NiAl matrix was selectively dissolved in an HCl:H2O2 solution to reveal W wires, which present various three-dimensional (3D) morphologies at different growth rates. The W fibrous phases in the NiAl–W alloy samples were then selectively removed with a mixed etchant of ammonium acetate to form a porous NiAl matrix at a constant potential. Dynamic corrosion curves revealed that etching W from the NiAl matrix was inhibited after 2–3?h. The porous structures of NiAl after removing W phases are linked to the 3D morphologies of W fibrous phases embedded in the NiAl matrix. The aspect ratio of W wires and the structures of porous NiAl can be adjusted by selecting the process parameters of this combined technology. |
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Keywords: | Alloy dissolution etching nanowires NiAl porous solidification tungsten |
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