Fundamental principles of spark plasma sintering of metals: Part I – Joule heating controlled by the evolution of powder resistivity and local current densities
Fundamental principles of spark plasma sintering of metals: Part I – Joule heating controlled by the evolution of powder resistivity and local current densities
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DOI：
10.1080/00325899.2019.1653532
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发表时间：
2019-08
影响因子：
1.4
通讯作者：
J. Trapp;B. Kieback
中科院分区：
文献类型：
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作者：
J. Trapp;B. Kieback
在这项研究中，研究了金属粉末在致密化过程中电阻率的演变，以及由此产生的电流在冲床、粉末压实器和模具中的流动。对伴随焦耳加热的评估表明，石墨冲头是提供90%以上热量的主要加热元件。冲头的高电阻和石墨模具的低电阻作为平行的电负载到试样上，决定了工具中的电流流动。对于具有完整氧化层的粉末颗粒，几乎没有电流流过致密体。另一方面，对于电阻率低于Ωcm的粉末，约50%的电流流过压块。尽管致密化过程中致密体的电阻率进一步降低，但该分数是恒定的。通过试样的恒定电流对于微观温度分布和理解所谓的“火花等离子体效应”具有重要意义。
In this study, the evolution of the electrical resistivity of metal powders during densification and the resulting current flow through punch, powder compact, and die is investigated. The evaluation of the accompanying Joule heating identifies the graphite punches as main heating element providing more than 90% of the heat. The high electrical resistance of the punches and the low resistance of the graphite die as parallel electrical load to the specimen determine the current flow in the tool. For powder particles with intact oxide layers, virtually no current flows through the compact. On the other hand, for a powder resistivity below Ωcm about 50% of the current flows through the compact. This fraction is constant despite further decreasing resistivity of the compact during densification. A constant current through the specimen has important implications for the microscopic temperature distribution and the understanding of the so-called ‘spark plasma effects’.