Thermally Activated Jamming in Ultrasonic Powder Compaction
Thermally Activated Jamming in Ultrasonic Powder Compaction
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DOI：
10.1002/adem.202001019
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发表时间：
2020-11
影响因子：
3.6
通讯作者：
A. A. Ward-A.;Christopher A. Hareland;Nathan E. Palmerio;Z. Cordero
中科院分区：
文献类型：
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作者：
A. A. Ward-A.;Christopher A. Hareland;Nathan E. Palmerio;Z. Cordero
通过比较名义上纯铜和热稳定性CuTa合金的致密化行为，评价了热软化在超声粉末压制中的作用。这些材料具有相似的热性能，但纯铜的软化温度比CuTA合金低得多。使用专门的超声波粉末压制装置，收集了相对密度、声极功耗和温度的现场测量，这些测量一起提供了反映压坯结构的随时间变化的几何硬化参数。纯铜粉的几何硬化数据显示了三个不同的致密化阶段：初始颗粒重排阶段；颗粒间形成强连接的堵塞过渡阶段；以及以协调塑性变形为特征的最后阶段。相比之下，热稳定的CuTA粉末的几何硬化数据表明，尽管经历了更高的常压、振荡幅度和温度，它仍然是一种弱流态化的颗粒介质。CuTa和CuTa粉末的对比行为表明，在超声粉末压制过程中，热激活的干扰转变驱动了颗粒间的连接生长和致密化。
Herein, the role of thermal softening in ultrasonic powder compaction is assessed by comparing the densification behaviors of nominally pure Cu and a thermally stable CuTa alloy. These materials have similar thermal properties, but pure Cu softens at much lower temperatures than does the CuTa alloy. Using a specialized ultrasonic powder compaction setup, in situ measurements of relative density, sonotrode power consumption, and temperature are collected, which together provide a time‐dependent geometric hardening parameter that reflects the structure of the compact. The geometric hardening data for the pure Cu powder reveal three distinct stages of densification: an initial particle rearrangement stage; a jamming transition where strong junctions develop between particles; and a final stage characterized by compatible plastic deformation. By contrast, the geometric hardening data for the thermally stable CuTa powder show that it remains a weak fluidized granular medium, despite experiencing higher normal pressures, oscillation amplitudes, and temperatures. The contrasting behaviors of the Cu and the CuTa powders suggest that a thermally activated jamming transition drives interparticle junction growth and densification in ultrasonic powder compaction.