Determination of Constitutive Equations for Titanium Alloys Applicable to Sheet Metal Formability.

摘要

A program to determine constitutive equations applicable to the sheet formability of the titanium alloy Ti-6Al-4V has been initiated. Load relaxation tests have been conducted at temperatures from 25 to 500 C over a strain-rate range of .1 to ten to the minus 8th power 1/sec using a programmable digital data acquisition system. The relaxation data, presented as log stress vs. log strain-rate hardness curves, illustrate the dependence of the strain-rate sensitivity, an important sheet metal formability index, on strain rate and temperature. The shapes of the hardness curves agree qualitatively with those predicted by the mechanical equation of state suggested by Hart. In particular, the transition from low temperature to high temperature grain matrix deformation behavior is clearly observed. Anomalous curvatures, apparently due to a strain aging mechanism, were observed in some room temperature hardness curves at low strain rates. (Author)