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.
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