The Rate (Time)-Dependent Behavior of Ti-7Al-2Cb-1Ta Titanium Alloy at Room Temperature Under Quasi-Static Monotonic and Cyclic Loading

Abstract

Uniaxial tests using a servocontrolled testing machine and strain measurement at the gage length were performed on a high-strength, low-ductility Titanium alloy. Tests involved monotonic and cyclic loadings with strain rates between 2 × 10−8 to 10−3 s−1 , stress rates from 10−1 to 102 MPa s−1 , repeated changes in strain rates, and short-term relaxation and creep tests. The inelastic behavior is strongly rate-dependent. Ratchetting is shown to increase as the stress rate decreases. No strain-rate history effect was found. A unique stress-strain curve is ultimately reached for a given strain rate irrespective of prior history as long as only positive stresses are imposed. In the plastic range the relaxation drop in a given time period depends only on the strain rate preceding the test and is independent of the actual stress and strain.