Thermally Activated Jamming in Ultrasonic Powder Compaction
Abstract
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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 18, 2020
- Source ID
- 10.1002/adem.202001019
Entities
People
- Austin A. Ward
- Christopher Hareland
- Nathan E. Palmerio
- Zachary C. Cordero
Organizations
- Army Research Office
- Massachusetts Institute of Technology
- Rice University