Hot working of Ti-17 titanium alloy with lamellar starting structure using 3-D processing maps

Abstract

Isothermal compression of Ti-17 titanium alloy with lamellar starting structure at the deformation temperatures ranging from 780 °C to 860 °C, the strain rates ranging from 0.001 to 10 s⁻¹, and the height reductions ranging from 15% to 75% with an interval 15% were carried out. Based on experimental results, 3-D processing maps including strain were developed and used to identify various microstructural mechanisms and distinguish the safe and unsafe domains. The processing maps exhibit two maximum power dissipation efficiency domains and dynamic globularization takes place in this two domains. The first domain occurs at 800–860 °C and at strain rates lower than 0.01 s⁻¹, and the second occurs at 780–800 °C and at strain rates lower than 0.01 s⁻¹. With the increasing of the strains, the values of maximum power dissipation efficiency in this two domains increase. One flow instability domain due to adiabatic shear bands and lamellar kinking occurs at strain rates higher than 0.487 s⁻¹, lower temperature, and higher strain above 0.2. The instability deformation region increases with increasing strain, strain rate, and decreasing temperature.