Compressive Deformation Behaviors of Coarse- and Ultrafine-Grained Pure Titanium at Different Temperatures: A Comparative Study

Abstract

The compressive deformation behavior and damage characteristics of ultrafine-grained (UFG) pure titanium produced by equal channel angular pressing (ECAP) and coarse-grained (CG) pure titanium were investigated and compared at temperatures ranging from 77 K (−196°C) to 873 K (600°C). It was found that the compressive stress-strain response and deformation damage morphologies exhibit quite different features for the UFG-Ti and CG-Ti, strongly depending upon the testing temperature. Different from the case of CG-Ti, the stress-strain curve of UFG-Ti exhibits a distinctive stage of strain softening, as the temperature is below recrystallization temperature (e.g. 77 K (−196°C) ∼423 K (150°C)). The yield stress and maximum flow stress of UFG-Ti are contrarily lower than those of CG-Ti, as the temperature is above recrystallization temperature. As compared to CG-Ti, UFG-Ti seems to exhibit more superior high-temperature deformation ability and a comparable low-temperature deformation capacity. The corresponding microstructural changes after compressive deformation of UFG-Ti and CG-Ti were also examined by TEM observations to interpret their differences in deformation micromechanisms.