Abstract
The distribution of dislocations in a titanium-10% molybdenum alloy after cold deformation and annealing has been studied using a decoration technique to reveal the dislocation sites. The technique has been previously described (5) and depends on heating the alloy in the β phase field followed by cooling at a fairly critical rate. Specimens have been deformed at various degrees of strain by cold rolling between 4 and 80 per cent reduction and subsequently reheated for increasing periods in the β phase field followed by cooling at the critical rate. In lightly deformed material recrystallization begins at the comparatively few points of high strain that occur at the intersection of deformation bands. At the same time sub-grains are formed in the lesser strained regions; the size of the sub-grains also seems to depend on the degree of strain and is smaller for higher strains. The new crystals grow preferentially along the deformation bands but also gradually absorb the surrounding sub-grains; islands of sub-grains may remain however even after prolonged annealing if the initial strain is slight. As growth proceeds dislocations appear to segregate into closely spaced arrays at some of the advancing boundaries. After high degrees of deformation and very short heating periods the microstructure shows a partly ordered network (mesh size ~ 0.3μ) that probably indicates the recovery stage. Further slight heating results in the nucleation of numerous new crystals scattered at many points. The new crystals grow rapidly and consume the surrounding network and the remaining dislocations are again accommodated in arrays at the boundaries. Continued heating results in further growth and it appears that during this process some dislocations are removed by interaction of the arrays at intersecting boundaries. Even after prolonged heating however some arrays remain.
Published Version
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