Influence of Grain Size on the Ductility of Age-Hardened Titanium Alloys

Abstract

In precipitation hardened alloys in which the moving dislocations are able to shear the particles pronounced slip bands are formed at the beginning of plastic deformation. With increasing volume fraction of precipitated particles such alloys often show a drastic reduction in macroscopic ductility. The reason for this brittle behavior is the high stress concentration at the head of dislocation pile-ups causing the fracture of grain boundaries by intersecting slip bands ^(1–3). The main purpose of the present work was to investigate how a reduction in grain size and therefore a decreasing number of piled-up dislocations within the slip bands may influence the ductility of those alloys. The investigation was mainly performed on two binary Ti-alloys, namely on ß-Ti-Mo and a-Ti-Al, because the details of deformation behavior and crack nucleation mechanisms are already known for these alloys ^(1,2).