Experimental Estimation of Maximal Ductility and Flow Curves of Titanium Alloys With Hot-Torsion Tests

Abstract

Purpose. The purpose of this work is to clarify the temperature-deformation modes of pressing pipes of titanium alloys (VT1-0, PT-7M, VT-14, VT-15, TS-5 and TS-6) and to determine the regression coefficients of the Hansel-Spittel equation by investigating plasticity and the deformation resistance during hot rotation of the specimens.Methodology. Studies on torsion were performed on a torsion test machine with a horizontal electronic force meter, with a maximum torque of 100 H × m, temperature. The maximum temperature of the test specimens was 1250 °C. Active capture of the test machine has a smooth rotation control from 5 to 200 rpm. Applying specimens with different aspect ratio to the length of the workpiece obtained a range of change of strain rates from 0.25 to 20 с-1.Findings. The main results of the study should be considered experimentally determined curves of the torque dependence on the angle of rotation of the sample to change the resistance of deformation of the metal, which allowed to clarify the temperature interval of maximum ductility during pressure treatment for alloys VT1-0, PT-7M, VT-14, VT-15, TS-5 and TS-6. Based on the data obtained on the deformation resistance, the coefficients of the Hansel-Spittel equation, which can be used to quantify the resulting stress in numerical simulation using the finite element method, have been statistically calculated.Originality. The data on experimentally determined regularities of influence of temperature-deformation modes of torsion on the change of the value of deformation resistance, which is characteristic of conditions of hot pressing of pipes, have been further developed. This allows to predict the power parameters of the deformation process, as well as to select the press equipment and improve the productivity of the press line.Practical implications. Studies on torsion have allowed to determine rational temperature-speed parameters of the process of pressing pipes from titanium alloys VT1-0, PT-7M, VT-14, VT-15, TS-5 and TS-6, for capacities of Ukrainian enterprises.