Tem investigation on dislocation dissociation and planar faults in deformed (Co, Ni)3Ti single crystal

Anomalous hardening and microstructural evolution accompanied by reordering and restoring of plastically deformed Co3Ti

“…For example, the cold-rolling texture of Co 3 Ti alloys was composed of strong α-fiber and weak β-fiber textures, in which the intensity of the {011}〈211〉 orientation was greater than those of the {112}〈111〉 and {123}〈634〉 orientations. The as-rolled microstructural features observed in this study were thus consistent with the previous observations [8][9][10]. In the sample with the peak hardness (Fig.…”

The Role of Twinning in Brittle Fracture Of Ti-Aluminides

“…L12 type and B2 type). The mono-laver twins and the extended stacking faults at a crack-tip may be sufficient enough for the energy absorption leading to transformation toughening, as was indicated in c_-Fe by Kohlhoff and Schmauder [26] and in Co3Ti by Liu et al [27]. Such an analysis for NiAI and FeAI is under way, which will be presented elsewhere 128].…”

Plastic deformation of chromium-modified L12Al3Ti. I. Flow behaviour

“…alloys having the f.c.c.-based L1 , crystal structure (Liu, Takasugi, Izumi andTakahashi 1988, Yamaguchi andUmakoshi 1990) and several characteristics seen in this flow behaviour are not seen in conventional f.c.c. alloys; Ni,Al-type alloys show a flow behaviour which is characterized by a strong anomalous flow peak at intermediate temperatures, Pt,Al-type alloys exhibit a flow behaviour in which the flow stress decreases rapidly with increasing temperature at low temperatures and becomes athermal at higher temperatures; Co,Ti-type alloys show a mixture of the Pt,AI-and Ni,Al-type characteristics, that is the flow stress decreases with increasing temperature at low temperatures but increases anomalously at intermediate temperatures.…”

“…For example, the flow behaviours of Co,Ti and Ni,Al are similar a t high temperatures but differ at low temperatures. Correspondingly, weak-beam (WB) transmission electron microscopy (TEM) studies (Liu et al 1988, Veyssiere 1989) have shown that the structures of the (1 10) superdislocations in the two materials are the same at high temperatures (both are dissociated into antiphase-boundary (APB)-coupled $( 110) superpartials), but different at low temperatures (the superdislocations are commonly dissociated into APB-coupled +( 110) superpartials in Ni,AI, but into superlatticeinstrinsic-stacking-fault (S1SF)-coupled *( 1 12) superpartials in Co,Ti). A similar type ofTEM study of dislocation structures in L1, A1,Ti-based alloys would be expected to shed light on these flow behaviours of the materials, but unfortunately the results of previous studies are often contradictory (for a review, see George, Pope, Fu and Schneibel (1991)) and, to date, no agreement has been reached.…”