Measurements of irradiation-induced creep in amorphous materials using in situ micropillar compression

2015-04-06
Özerinç, Sezer
Kim, Hoe Joon
Averback, Robert
King, William
This presentation describes in situ measurements of irradiation-induced compression creep on amorphous (a-) Cu56Ti38Ag6, Zr52Ni48, Si, and SiO2 micropillars bombarded with ~2 MeV Ne+, Ar+, and Kr+ ions at room temperature. We have employed a custom mechanical testing apparatus1 which is composed of a nanopositioner, a doubly-clamped silicon beam transducer, and an interferometric laser displacement sensor. The apparatus has a displacement resolution of 1 nm and force resolution of 1 mu;N. Amorphous Cu56Ti38Ag6 samples were prepared by ball milling and single crystal Si microposts were fabricated by deep reactive-ion etching. Amorphous Zr52Ni48 and SiO2 were deposited on Si microposts through magnetron sputtering and plasma enhanced chemical vapor deposition. Silicon samples were amorphized by pre-irradiation. The micropillars of 1 mu;m diameter and 2 mu;m height were milled by using a focused ion beam, and amorphous structure of the samples were verified by electron diffraction and X-ray diffraction analyses. We have observed Newtonian flow in the stress range 50-600 MPa and determined that for point defect mediated creep, irradiation-induced fluidity is asymp;3 GPa-1dpa-1 irrespective of the material and bombarding ion. When the electron mobility of the material is low and electronic stopping power is above a certain threshold, stress relaxation through thermal spikes can also contribute to creep, increasing the fluidity. Measurements on Ar+ and Ne+ irradiated a-SiO2 have resulted in fluidities of 35 and 83 GPa-1dpa-1, demonstrating the additional effect of thermal spikes. Measurement results corresponding to point defect mediated creep are in very good agreement with molecular dynamics simulation predictions2 and previous stress relaxation measurements3. We quantitatively explain the additional contribution of electronic stopping by using a previous model of stress relaxation in thermal spikes4. MeV heavy ion irradiation of micron-sized specimens results in unique combinations of electronic and nuclear stopping and provides an effective approach to the analysis of irradiation-induced creep.
Citation Formats
S. Özerinç, H. J. Kim, R. Averback, and W. King, “Measurements of irradiation-induced creep in amorphous materials using in situ micropillar compression,” presented at the 2015 MRS Spring Meeting & Exhibit, April 6-10, 2015, San Francisco, California, USA, 2015, Accessed: 00, 2021. [Online]. Available: https://www.mrs.org/spring-2015/program-session/?code=XX.