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Germann, Timothy C

Publications and source records attributed to Germann, Timothy C.

At least 19 records

The Influence of Grain Boundary Type upon Damage Evolution at Grain Boundary Interfaces

In a prior work, it was found that grain boundary structure strongly influences damage evolution at grain boundaries in copper samples subjected to either shock compression or incipient spall. Here, several grain boundaries with different grain boundary structures, including a {Sigma}3 (10-1) boundary, are interrogated via conventional transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) to investigate the effects of atomic-scale structural differences on grain boundary strength and mobility. Boundaries are studied both before and after shock compression at a peak shock stress of 10 GPa. Results of the TEM and HRTEM work are used in conjunction with MD modeling to propose a model for shock-induced damage evolution at grain boundary interfaces that is dependent upon coincidence.

36 MATERIALS SCIENCE↗

Mechanism for recombination of radiation-induced point defects at interphase boundaries

MD studies of collision cascades in KS-type Cu-Nb interfaces are performed, revealing that Cu interstitials are preferentially loaded into the interface while on the bcc Nb side there is very little absorption of interstitials. The interstitial loading effect at two types of heterogeneous Cu-Nb interfaces, both KS-type and SPD {l_brace}112{r_brace}-type interfaces is studied: (a) The Cu interstitials are observed to spontaneously emit from both types of interfaces to annihilate vacancies in the nearby bulk, (b) MD and NEB studies are used to characterize low barrier emission processes. Our study also indicates that interstitials do not lose their identity when absorbed even at interfaces where they become significantly delocalized.

36 MATERIALS SCIENCE↗