The effect of prestrain on low and high temperature creep in Ti834

The low and high temperature creep properties of the (alpha+beta titanium alloy Ti834 have been studied for various levels of applied plastic prestrain. Evidence is shown that the prestrain at room temperature causes the formation of quasi-cleavage facets in a manner described by the Evans-Bache model. These facets are also produced when the material is creep tested at room temperature, although larger areas of faceting are found. The applied prestrain causes a drop in the strain at failure at room temperature due to a high dislocation density inhibiting further movement of dislocations. At high temperature this increase in applied prestrain results in an accelerated creep rate. This is attributed to a number of issues, including increased thermal energy allowing greater dislocation recovery and mobility. Swaged Ti834 material is also considered and is shown to behave similar to highly prestrained material with evidence of strain hardening and reduced cold creep rate. (C) 2010 Elsevier B.V. All rights reserved.