A Comparison of Temperature-Dependent Compressive Deformation Features of Ultrafine-Grained Ti and Cu Produced by ECAP

Abstract

The temperature-dependent deformation and damage behaviors of ultrafine-grained (UFG) Cu and Ti produced by equal channel angular pressing (ECAP) were investigated and compared. It was found that ECAPed materials with different crystalline structures, e.g. the present fcc Cu and hcp Ti, exhibited significantly distinctive high-temperature deformation and damage characteristics. As the testing temperature is below recrystallization, small- and large-scale cracks or voids formed along the shear bands (SBs) on the surface of UFG Cu, whereas only a few fine shear lines and some non-propagation voids appeared on the surface of UFG Ti. As the temperature is above recrystallization, some small cracks (or voids) formed along grain boundaries and slip deformation took place in many coarsened grains, while only extrusions and intrusions instead of obvious cracks or voids are observable for UFG Ti. The corresponding microstructual changes after compressive deformation, e.g. grain coarsening, were also examined and confirmed by TEM observations.

Temperature-Dependent Compressive Deformation Behavior of Commercially Pure Iron Processed by ECAP

“…2). Although the growth of grains will promote the occurrence of dislocation slip [16], the remaining of lath structures produced during ECAP processing, as well as a lot of dislocations in the cells and the laths (Fig. 11d-f), still leads to the occurrence of shear deformation, but secondary shear bands are not well developed.…”

“…Similarly, the work by Valiev et al [15] indicated that controlled annealing could bring about a 30% increase in strength of nanostructured SPD titanium simultaneously with enhanced ductility as compared to the case of as-produced state. However, some investigations [10,16,17] revealed that the microstructural stability of UFG materials produced by SPD also depended upon their crystalline structures. For example, Jiang et al [16] compared deformation characteristics and microstructures of UFG CP Cu and Ti at comparative temperatures.…”

“…However, some investigations [10,16,17] revealed that the microstructural stability of UFG materials produced by SPD also depended upon their crystalline structures. For example, Jiang et al [16] compared deformation characteristics and microstructures of UFG CP Cu and Ti at comparative temperatures. They found that small-and large-scale cracks or voids were formed along the shear bands (SBs) on the surface of UFG Cu, whereas only a few fine shear lines and some non-propagation voids appeared on the surface of UFG Ti at temperatures below recrystallization temperature.…”

“…So far, with regard to the studies of the temperature effect on mechanical behavior of UFG materials, the adopted materials basically have face-centered cubic (FCC) and hexagonal close-packed (HCP) structures with commercial purity [8][9][10][16][17][18] due to extensive applications of these two sorts of structural materials in engineering and their notable differences in structural stability. However, there are as yet almost no research findings on the temperature-dependent mechanical behavior of fine-grained or UFG materials with a body-centered cubic (BCC) structure.…”