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Wrought TiAI products manufactured by conventional hot-working procedures, such as forging and extrusion, suffer from structural and chemical inhornogeneities, which are major concerns for the reliability of components. In an attempt to overcome these problems, TiAI alloys were hot worked by torsional deformation. Using this method, a much higher strain and mechanical work can be imparted, which triggers dynamic recrystallization. The metallurgical potential of this technique will be assessed. Particular emphasis is placed on shear localization processes, which often lead to premature failure of the workpiece. [ABSTRACT FROM AUTHOR]

Mechanical twinning has long been recognized as an important deformation mechanism in many intermetallics including γ(TiAl) based alloys. The generation of a twin can be triggered by dislocations at grain boundaries. The reduction of the stored strain energy in relation to a configuration without any twins can be shown by applying an established transformation criterion, considering twinning as a transformation shearing process. In addition, the application of a thermodynamical extremal principle allows one to predict a distinct twin nucleus in good agreement with experimental observations. The concept is rather general and can be adapted to any initial eigenstress field produced by dislocations present at misfitting interfaces. [Copyright &y& Elsevier]