Local Modification of Cu Microwires by Joule Heating

Tohmyoh, Hironori; Ishihara, Mitsuharu

doi:10.7567/apex.6.077302

Cited by 6 publications

(7 citation statements)

References 25 publications

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“…Joule-heating by supplying a current to wire is known to be an effective method for the heat treatment of thin wire [13][14][15][16][17][18][19]. Because copper has a small heat capacity (0.385 J/g o C), the temperature of small-scale copper wire can be easily increased by passing a current [20].…”

Section: Introductionmentioning

confidence: 99%

“…Because copper has a small heat capacity (0.385 J/g o C), the temperature of small-scale copper wire can be easily increased by passing a current [20]. It has been reported that normal copper wires can be softened by Joule-heating [19,20], and that grains grow faster than with heat treatment using a conventional furnace [13,20]. Tohmyoh et al [20] reported that during the Joule-heating of copper microwires, yield strength decreased as the grain size increased.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Joule-Heating Treatment on the Microstructure and Physical Properties of 16-Stranded Compressed Copper Wires

Choi¹,

Im²,

Kang³

et al. 2021

Korean J. Met. Mater.

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Compressed wires are produced by cross-sectionally compressing stranded conductors, which results in a smaller conductor diameter. This also leads to a lower weight wire, because a thinner external insulated coating can be used, compared to the low-voltage wires typically used in automobiles. However, a post production heat treatment of the compressed wires is required because plastic deformation occurs during compression after drawing the wires. In this study, the work hardening of stranded compressed copper wires was controlled by Joule-heating, and the resulting changes in microstructure, mechanical, and electrical properties after various annealing voltages (0, 25, 27, 31, 35, and 39 V) were observed. The results confirmed that as the annealing voltage increased from 0 to 31 V, the anisotropic deformation texture with a <111> orientation as the main component was reduced, and micrograins were generated throughout the stranded wires via recrystallization. At an annealing voltage above 31 V, the grains grew to be more than twice as large as those before heat treatment. At an annealing voltage of 31 V these structural changes contribute to the elongation increase of the compressed wires to 28.34%, and an improvement in electrical resistance to 145.85 mΩ.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Joule-Heating Treatment on the Microstructure and Physical Properties of 16-Stranded Compressed Copper Wires

Choi¹,

Im²,

Kang³

et al. 2021

Korean J. Met. Mater.

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“…The physical properties of Cu microwires are sensitive to the crystalline structure 27)- 32) , and thus, controlling the structure of the wire is a useful way of enabling the wires to be used for various purposes. It has been reported that Cu microwires can be softened by Joule heating 25) , and that the Cu grains grow faster by Joule heating compared with the heat treatment with a conventional furnace 26) .…”

Section: Introductionmentioning

confidence: 99%

The Mechanical Properties of Polycrystalline Cu Microwires Having the Crystal Grains Grown by Joule Heating

Tohmyoh

Fukuda

Kimura

2019

J. Soc. Mat. Sci., Japan

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This paper reports on the relationship between the mechanical properties and the grain size of Cu microwires modified by Joule heating. The increase in yield strength as the grain size of a metal or alloy decreases is known as the Hall-Petch relation. Because the crystal grain size in thin metallic wires is fine, these have higher strength compared to their bulk counterparts. To improve the formability of 25 m-thick Cu microwires, the wires were heat-treated at various temperatures by Joule heating, and the grain size of the wires was evaluated quantitatively by cross section method. Larger crystal grains grew at higher temperatures, and the wire heat-treated at the highest temperature of 600 o C had a bamboo structure, in which the grain boundaries were only in the radial direction of the wire. Small-span, three-point bending tests were performed on the heat-treated Cu microwires to determine their mechanical properties. The Young's modulus of the wires was found to be independent of grain size, with an average value of 86.4 ± 2.4 GPa. On the other hand, the yield stress of the wires clearly depended on the grain size. The yield stress of a Cu microwire that had not been subjected to Joule heating was 311 MPa, and this decreased to 75 MPa after heat treatment at 600 o C. Finally, we confirmed that the Hall-Petch relation was applicable to the Cu microwires, except for those that, due to insufficient heat treatment, had crystal grain structures in which the grains were highly elongated in the axial direction of the wire.

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“…Of the available techniques for joining small scale materials together, that utilizing Joule heat can be used in various situations to join micro or nanowires (Tohmyoh, et al, 2007) or carbon nanotubes (Hirayama, et al, 2001;Dong, et al, 2007;Jin, et al, 2007), etc. Joule heat has also been used to solder nanowires (Peng, et al, 2009) and to structurally modify thin wires (Hummelgård, et al, 2010;Tohmyoh and Ishihara, 2013).…”

Section: Introductionmentioning

confidence: 99%

Joule heat welding of thin wires to thin films

Tohmyoh

Fujimori

2014

Mechanical Engineering Journal

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To effectively use micro or nano materials and create advanced materials systems from them, welding techniques for such small scale materials are vital. For this purpose, the tips of two thin wires were welded together with Joule heat and the conditions required to achieve it was discovered experimentally. In this paper, the Joule heat welding of thin wires to thin films deposited on substrates is described. To derive the conditions required to achieve this, a heat conduction model for a cylindrical element in the film located at the contact between the wire and the film is considered and the critical thickness of the film above which the welding conditions are independent of film thickness is derived analytically. The validity of the heat conduction model was experimentally verified by welding 0.8 m diameter Pt wires onto thin Pt films on electrically-insulated substrates. The experiments are performed for various combinations of the length of the wire and the thickness of the films. The current required for welding the wires onto the films having the thickness over the critical thickness are investigated and the conditions required for the welding are found to be coincident with those for welding the tips of two wires with Joule heat.

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Local Modification of Cu Microwires by Joule Heating

Cited by 6 publications

References 25 publications

Effect of Joule-Heating Treatment on the Microstructure and Physical Properties of 16-Stranded Compressed Copper Wires

Effect of Joule-Heating Treatment on the Microstructure and Physical Properties of 16-Stranded Compressed Copper Wires

The Mechanical Properties of Polycrystalline Cu Microwires Having the Crystal Grains Grown by Joule Heating

Joule heat welding of thin wires to thin films

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