The effects of Mg doping on the microstructure and transport properties of internal tin-processed brass matrix Nb3Sn superconductors
The effects of Mg doping on the microstructure and transport properties of internal tin-processed brass matrix Nb3Sn superconductors
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DOI：
10.1088/1361-6668/aaf61a
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发表时间：
2019-01
影响因子：
3.6
通讯作者：
Zhou Yu;N. Banno;Yong Zhao;K. Tachikawa
中科院分区：
文献类型：
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作者：
Zhou Yu;N. Banno;Yong Zhao;K. Tachikawa
在Cu基体中加入Zn可提高Sn的活性，加速Nb_3Sn层的形成。然而，在我们的样品中，Ti掺杂在Sn芯中，并且在反应期间，观察到Ti积聚在1980-Nb芯多芯黄铜基体线材的内部和外部子元素之间。随着Mg加入到黄铜基体中，子元素之间的Ti积累被显着抑制，这促进了Ti并入Nb 3Sn层。同时，所形成的Nb 3Sn层显示出较小的晶粒尺寸。与黄铜（Cu-12wt%Zn）基线材相比，Cu-12 Zn-0.2Mg基线材的临界电流密度（Jc）有所提高，这是由于Nb 3Sn层中Ti的引入和Nb 3Sn晶粒尺寸的细化。通过分析Jc（B）曲线，由克雷默图计算了不可逆场（Birr）和最大体钉扎力（Fp，max）。少量Mg（0.2wt%）掺杂到Cu-12 Zn基质线中可以在670 °C和730 °C之间热处理线之后使Birr值增加约0.5T，并且使Fp，max值增加约3. 4GN m-3。Cu-12 Zn-0.2Mg基线材的非Cu Jc在685 °C热处理后达到最大值1533 A mm− 2@12 T，并在更高温度下降低。
The addition of Zn into Cu matrix has been proved to enhance the Sn activity and accelerate the formation of a Nb3Sn layer in internal tin-processed Nb3Sn wires. However, in our samples, Ti is doped in Sn cores, and during the reaction, Ti was observed to accumulate between the inner and outer sub-elements of the 1980-Nb-core multi-filamentary brass matrix wires. With the addition of Mg into the brass matrix, Ti accumulation between the sub-elements was significantly suppressed, which promoted Ti incorporation into the Nb3Sn layers. Meanwhile, the formed Nb3Sn layers exhibited smaller grain sizes. Compared to the brass (Cu-12wt%Zn) matrix wires, an improvement of critical current density (Jc) was found in the Cu-12Zn-0.2Mg matrix wires due to the incorporation of Ti into the Nb3Sn layer and the refinement of the Nb3Sn grain size. The irreversibility field (Birr) and maximum bulk pinning forces (Fp,max) were calculated from the Kramer plot by analyzing the Jc(B) curves. A small amount of Mg (0.2 wt%) doping into the Cu-12Zn matrix wires can increase the Birr value by about 0.5 T and the Fp,max value by about 3 ∼ 4 GN m−3 after the wires were heat treated between 670 °C and 730 °C. The non-Cu Jc of the Cu-12Zn-0.2Mg matrix wires reaches the maximum value of 1533 A mm−2 @12 T after heat treatment at 685 °C and decreases at higher temperatures.