Study of dislocations in NiAl through the use of in-situ straining in transmission electron microscopy

In order to understand the effect of composition, orientation and cooling rate on dislocation behavior in NiAl, high and commercial purity Ni–Al single crystals have been strained in-situ in transmission electron microscopy. In all materials tested, dislocations are generated from the edges of the foils and from deep in the foil interiors and glide in slip bands. Cross-slip of mobile dislocations is often observed in high purity material, whereas in commercial purity material slip was found to be much more planar. Dislocations moved by rapid jumps in the high purity material, in contrast to the commercially pure material, where movement was much slower and uniform. Despite the well known effect of thermal history on the mechanical behavior of NiAl, variations in cooling rate of the commercially pure material did not appear to influence the dislocation behavior.