The morphology and interface configuration of Ti5Si3 precipitates and TiAl matrix were characterized by bright field imaging and HRTEM (see attached image). No orientation relationship was found probably due to a relatively large size of Ti5Si3. In HRTEM image, the lattice fringe normal to the interface was determined to {11-20} Ti5Si3 plane with a interplanar spacing of 0.3732 nm. Note that the spacing of {001} TiAl plane is 0.4071 nm. Can we conclude that there is an orientation relationship of {11-20} Ti5Si3 // {001} TiAl at the initial precipitation stage and the relationship would be destroyed by coarsening of Ti5Si3 precipitates? This issue is experimentally supported if we reconstruct the {11-20} Ti5Si3 lattice fringe using spatial frequencies of {11-20} Ti5Si3.
Dear Volker, HRTEM and SAED did not reveal any possible orientation relationship. We reconstruct the {11-20} Ti5Si3 lattice fringe, and find the trace of {11-20} Ti5Si3 // {001} TiAl. It is therefore speculated that coarsening of Ti5Si3 particle destroyed the possible orientation of {11-20} Ti5Si3 // {001} TiAl which has been reported before.
Hi, Hao. I think the orientation relationship could be deviated from rational one, so that you can not obtain the lattice fringe in two phase simultaneously. However, ou can precisely determine the OR by kikuchi line. By the way, the OR deviate from rational one does not mean there is no orientation relationship between two phases. When we say there is no OR, it means there are no reproducible OR.
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