Gleeble Testing of Tungsten Samples
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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The development of a bulk nano-grained tungsten material has been the subject of ongoing research at the U.S. Army Research Laboratory ARL, Aberdeen Proving Ground, MD. While it has been shown that a powder metallurgy approach can lead to bulk nano-grained tungsten material 1, 2, it has been a persistent challenge to achieve full density. Commercially available tungsten must undergo complex multi-step processes both hot and cold working to obtain a fully dense part 3. Similar procedures may need to be developed to produce fully dense nano-crystalline tungsten. One problem with post-processing procedures is that bulk nano-grained materials are often less ductile than their large grained counterparts 4. With conventional commercial tungsten, the brittle nature of the material is overcome by incorporating multi-step hot working procedures. However, for nano-tungsten, recrystallization and grain growth become an issue during processing at elevated temperatures. Commercially, rhenium is often added to tungsten to improve ductility and high temperature stability 5. By adding rhenium to nano-tungsten, enough ductility might be developed to allow for hot working at temperatures low enough to prevent grain growth. Prior to swaging, it needs to be determined whether or not the rhenium addition does impart ductility to nano-tungsten and, if so, at what temperatures and conditions. In order to test the mechanical properties of nano-tungsten with rhenium at high temperatures, the Gleeble unit a digital version of the 1500 model produced by Dynamic Systems Incorporated, Poestenkill, New York at ARL was used. The Gleeble is a process simulation machine designed to mimic the thermal and mechanical conditions that arise during processing 6, 7.
- Metallurgy and Metallography