{111} Glide in Ni₃Al at room temperature.In situobservations under weak-beam conditions

Some aspects of cross-slip mechanisms in metals and alloys

“…The origin of the strength anomaly is thus an increase in the difficulty of cross slipping as the temperature rises due to an increase of the recombination energy R. In the elastic approximation, this would correspond to a decrease of the stacking fault energy as the temperature is increased. Similar behaviour has also been observed in a nickel based alloy [38], in the case of glide in {100} planes, and the same mechanism could also be at the origin of the strength anomaly of Ni3Al, in the case of {111 } glide [39]. It can also account for the thermally activated dislocation motion evidenced at the strength anomaly [43].…”

“…In the case of glide in { 111 } planes, the locking-unlocking movement is interpreted in a similar way, with a stable sessile configuration spread into thé {111} cross slip plane and a metastable glissile configuration spread in thé {111} glide plane [39]. independent of the dislocation length L.…”

In situ straining experiments in weak-beam conditions

“…It is thus important to image the two components of superdislocations during deformation. In Ni3Al and nickel-based intermetallic alloys, the dissociation width of superdislocations ranges between 4 [13] [13] have been observed post-mortem [18,19], and jumps over distances scaling with the dissociation width have also been evidenced by the post-mortem observation of a high density of macrokinks similar to MK in figure 4 [20].…”

In situ deformation and description of mechanical behaviors in Ni3Al

“…For one reason, a difficulty arises due to the fact that superdislocations move too fast to obtain direct evidence for the proposed strengthening mechanism at high temperatures (Nemoto et al, 1980). According to the recent in situ experiments by Caillard et al (1988), and Molenat and Caillard (1992) figure 2. This device is designed to make control of the stress level precise by use of a spring.…”

“…A high voltage electron microscope is shown to be useful in examining dislocation motion in the state close to bulk samples , Tabata and Fujita, 1972, Fujita and Ueda, 1972, Mori and Fujita, 1977, Tabata et al,1977, Martin and Kubin, 1979. Radiation damage may, however, ruin the original characteristics.…”