The Tensile Mechanical Properties of Thermomechanically Consolidated Titanium at Different Strain Rates

The microstructures, tensile mechanical properties, and fracture behavior of a commercially pure (CP) titanium disk (called PF/Ti disk) and a CP titanium bar (called PE/Ti bar) made by powder compact forging (PCF) and powder compact extrusion (PCE) respectively have been studied. With increasing the strain rate from 10⁻⁴ to 10⁻¹ s⁻¹, the yield strength of the PF/Ti disk and PE/Ti bar increased from 708 to 811 MPa and from 672 to 764 MPa, respectively; their UTS increased from 824 to 1009 MPa and from 809 to 926 MPa, respectively, and their elongation to fracture decreased from 21 to 8 pct and from 25 to 17.8 pct, respectively. With a low strain rate of 10⁻⁴ s⁻¹, the PF/Ti disk did not show any cavities at unbonded or weakly bonded interparticle boundaries, but the PE/Ti bar showed a small number of cavities with sizes of around 1 μm. With a high strain rate of 10⁻² s⁻¹, the PF/Ti disk showed a small number of cavities with sizes in the range of 0.1 to 0.5 μm, while for the PE/Ti bar, the cavities grew into microcracks of up to 20 μm long. The findings suggest that close to 100 pct of consolidation is rapidly achieved by PCF at 1573 K (1300 °C) and PCE at 1523 K (1250 °C), respectively, possibly due to the dissolution of the particle oxide surface films during heating and rapid diffusion bonding between the fresh particle surfaces during PCF and PCE.