About this Abstract |
| Meeting |
MS&T26: Materials Science & Technology
|
| Symposium
|
Grain Boundaries, Interfaces, and Surfaces: Fundamental Structure-Property-Performance Relationships
|
| Presentation Title |
Grain Boundary Structure Governs Stress-Induced Hydride Nucleation and Crack Initiation in Titanium: An In Situ TEM Study |
| Author(s) |
Vivek Devulapalli, Johann Michler, Xavier Maeder |
| On-Site Speaker (Planned) |
Vivek Devulapalli |
| Abstract Scope |
Grain boundaries in titanium actively govern phase transformation and failure mechanisms under stress. Building on the discovery that solute segregation induces topological GB phase transitions in Ti through icosahedral Fe-rich cage structures, the present work extends this interface-centric framework to stress-driven hydride nucleation. Using in situ TEM tensile testing of bicrystalline Ti specimens, we directly observe real-time nucleation and growth of cubic titanium hydride precipitates, with hydrogen introduced during FIB-based sample preparation. Precession electron diffraction mapping combined with HRTEM establishes that specific GB facets and facet junctions act as preferential nucleation sites, drawing a direct parallel to the site-selectivity observed in segregation-induced GB phase transitions. Hydride growth arrests upon impingement with GB planes, immediately triggering crack initiation at the hydride-matrix interface due to severe elastic mismatch. The crack propagation mode, intergranular versus transgranular, is dictated by GB facet geometry, where highly faceted boundaries deflect cracks transgranularly, retarding propagation. |