Determination and Modeling of the Plastic-Flow Behavior of a Strain- and Strain-Rate-Hardening Material via the Constant-Stress, Constant-Heating-Rate Test

The high-temperature plastic-flow behavior of a strain- and strain-rate-hardening material was quantified using a novel, high-throughput technique known as the constant-stress, constant-heating-rate (CSCHR) test. For this purpose, CSCHR experiments were performed on annealed sheet of unalloyed (Type 1) niobium using three constant-stress levels (34, 69, and 103 MPa) and two heating rates (15 and 63 °C/min). To interpret the observations, a suite of relations was derived to enable the extraction of the material coefficients that describe the constitutive behavior (i.e., apparent activation energy Q, strain hardening exponent p, strain-rate sensitivity exponent m) from the CSCHR measurements. Among other things, the relations revealed that the value of Q is a function of the slope of the Arrhenius plot as well as a term dependent on the ratio of p to m. It was also demonstrated that the same material coefficients describing behavior during the continuous heating imposed during CSCHR tests were applicable for quantifying deformation under isothermal, constant-strain-rate conditions within a reasonable engineering accuracy.