The Deformation-DIA: A Novel Apparatus for Measuring the Strength of Materials at High Strain to Pressures at Elevated Temperature

Abstract

The primary focus of this 3-year project was to develop and put to use an instrument to test experimentally the effect of pressure on body centered cubic (BCC) metals and other materials of interest to the Stockpile Stewardship program. Well-resolved materials testing requires measurements of load and deformation rate be measured at separable conditions of temperature, pressure, and plastic strain. The new apparatus at the heart of this work, the Deformation-DIA (D-DIA), began the project as a design concept. Its principal feature would be the capability to extend the conditions for such controlled materials testing from the current pressure limit of about 3 to almost 15 GPa, a factor of 5 increase. Once constructed and successfully tested, the plan of the project was to deform samples of BCC metals at arbitrary temperature and high pressures in order to provide preliminary measurements of strength and to prove its worth to the Stockpile Stewardship program. The project has been a stunning success. Progress toward demonstrating the worth of the D-DIA as a workhorse instrument for materials strength measurement at high pressure was given a huge boost by the fact that the machine itself functioned flawlessly from the very start, allowing the investigators to focus on measurement quality rather than technical operational issues. By the end of the project, we had deformed several samples of polycrystalline molybdenum (Mo) and tantalum (Ta) under very precisely controlled conditions, and for the Ta, had produced the first rudimentary measurements of strength to pressures of 8 GPa