Procedure of Determining the Rheological Properties of Metals by Torsion Tests

Abstract

The quality of results of mathematical modeling the pressure treatment of metals (PTM) substantially depends on the exactness of the initial data, which include the rheological properties of the billet material. The traditional procedure of their testing is based on the assumption that the sample temperature remains constant during testing. However, it is known that strain sample heating occurs during isothermal loading. Modern plastometers do not foresee monitoring the sample temperature during testing, which introduces the substantial error when calculating the deformation resistances and, correspondingly, temperature
fields and energy-power parameters of PTM processes. In connection with this, the procedure and results of the experimental investigation into the heat liberation in the samples made of the VT-6 titanium alloy under torsion using a laboratory torsion plastometer in a temperature range of 800–1000 °C at deformation rates of 0,01–10,0 s–1 (1–600 rpm) are presented in this article. The temperature of the sample surface was monitored using a photopyrometer during testing. It is established that the sample surface substantially heats at relatively high loading rates, and the temperature increment to the destroy instant can reach 50–60 °C at the testing rate of the order of 10 s–1 and initial temperature of 850 °C. The error in determining the strain resistance is of the order of 30 %.