Structure of 1/2{l_angle}110{r_angle} dislocations in {gamma}-TiAl by high resolution TEM and embedded atom method modelling
- Materials Directorate WL/MLLM, Wright Patterson AFB, OH (United States)
- Ohio State Univ., Columbus, OH (United States)
High Resolution TEM (HRTEM) observations of a dislocation in {gamma}-TiAl are compared directly with atomistic calculations of dislocation structures performed with atomistic potentials in order to obtain an estimate of the Complex Stacking Fault Energy ({gamma}{sub csf}). A value of between 470 and 620 MJ/M{sup 2} was obtained. HRTEM observations are presented of a Ti-52Al sample, containing a dislocation with Burgers vector 1/2{l_angle}110{r_angle} and 60{degree} line orientation. This image is matched against images simulated from the outputs of Embedded Atom Method (EAM) simulations, using potentials that were fit to bulk {gamma}-TiAl properties. Two atomistic simulation methods were employed in order to give the range of values for {gamma}{sub csf}. In the first of these methods, three EAM potentials were used to simulate the stress-free core structure. These were fit so as to produce three different values of all other properties being roughly the same as the literature values for {gamma}-TiAl. All of these potentials produced cores that were more extended than the experimental observation. Thus a value of 470 mJ/M{sup 2}, being the highest value of {gamma}{sub csf} obtainable for the EAM potentials, is reported as a low limit estimate of {gamma}{sub csf} for {gamma}-TiAl. An upper limit estimate of the value of {gamma}{sub csf} was obtained by applying an external `Escaig` stress that forced the Shockley partials to further constrict, simulating the effect of an increase in {gamma}{sub csf}. The preliminary value calculated from this procedure was 620 MJ/M{sup 2}.
- Research Organization:
- Sandia National Laboratory
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 78312
- Report Number(s):
- CONF-941144--; ISBN 1-55899-265-0
- Country of Publication:
- United States
- Language:
- English
Similar Records
Embedded atom method simulation of 1/2{l_angle}110{r_angle} dislocation core structures
Interfacial energies in two-phase TiAl-Ti{sub 3}Al alloy