ABSTRACT 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’.

中文翻译：

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金属放电等离子烧结的基本原理：第 I 部分 – 由粉末电阻率和局部电流密度的演变控制的焦耳热

摘要 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流过冲头、粉末压块和模具的电流。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样品的平行电负载决定了工具中的电流。对于具有完整氧化层的粉末颗粒，几乎没有电流流过压块。另一方面，对于低于 Ωcm 的粉末电阻率，大约 50% 的电流流过压块。尽管在致密化过程中压块的电阻率进一步降低，但该分数是恒定的。