EFFECT OF LAMELLAR SPACING ON DEFORMATION-BEHAVIOR OF UNIDIRECTIONALLY SOLIDIFIED, TWIN PHASE TIAL

Unidirectional solidificatton has been employed to cast Ti-Al specimen s containing Ti-Al lamellae separated by narrow Ti3Al lamellae. These lamellae were parallel and continuous throughout the specimens. Two di fferent compositions, Ti-49.1 at.-%Al and Ti-50.8 at.-%Al, were used s ince the differing compositions resulted in different spacing between the lamellae, the latter displaying a wider spacing. Specimens were ro lled with the plane of the lamellae parallel to and at 45-degrees to t he rolling plane in order to assess how ductility is affected by lamel lar spacing and the direction of slip relative to the lamellae. Deform ation was found to be highly anisotropic; ductility being greater when slip occurred in a direction parallel to the lamellae than when slip occurred in a direction at 45-degrees to the lamellae. Reducing the wi dth of the lamellae resulted in an improvement in ductility in both ea sy and difficult slip directions and this has been attributed to a red uction in the concentration of stress at lamellar boundaries.