In situ observations of unusual dislocation mechanisms in the intermetallic alloy Ti3Al

In situ straining experiments in a transmission electron microscope have been carried out on a Ti3Al intermetallic alloy, with the aim of determining the microscopic mechanisms controlling glide in prism, basal and pyramidal planes. Five different antiphase boundary energies have been measured and compared with the corresponding densities of incorrect first nearest neighbour atoms. The determination of a tension-compression asymmetry in pyramidal slip, and the detailed analysis of the complex microscopic mechanisms involved illustrate the efficiency of in situ experiments to solve complex problems in plasticity. A comparison between the properties of the different slip systems shows that they are controlled by different microscopic mechanisms, none of them being of covalent origin.