The hyperbolic constitutive equations and modified dynamic material model of TiBw/Ti-6.5Al-2.5Zr-1Mo-1V-0.5Si composites

Abstract

The hot deformation behaviors TiBw/Ti-6.5Al-2.5Zr-1Mo-1V-0.5Si composite were studied via hot compression tests at the temperature ranged from 870 °C to 1100 °C and strain rate ranged from 1 s−1 to 0.001 s−1. Hyperbolic constitutive equations were calculated for α+β and β phase region respectively. The processing maps were constructed based on a modified dynamic material modeling (MDMM), in which an integration method bonded by linear regression was employed to reduce the uncertainty caused by interpolation. The microstructure evolution of metallic matrix and TiBw reinforcement were investigated by scanning electronic microscopy and transmitting electronic microscopy. The hot deformation activation energy of the present composite was determined to be 593.7 kJ mol−1 in α+β region and 338.1 kJ mol−1 in β region. No trace of macroscopic defects was found on the compressed specimens, showing the present composite has a good workability. The ideal hot working regions for the present composite are 0.003 s−1/900 °C and 0.06 s−1/950 °C in α+β region, 0.003 s−1/1020 °C and 0.01 s−1/1060 °C in β phase region. The refinement in microstructure was caused by globularization and dynamic recrystallization, which also caused the peaks of heat dissipation efficiency in the processing maps. The flow of metallic matrix lead to the rotation of TiBw, forming a sharp (1 0 0)TiBw || CD texture. TiBw fracture was caused by the stress concentration induced by dislocation pileups around them, and the fracture of TiBw can be reduced by decreasing strain rate or increasing deformation temperature.