Fracture toughness at cryogenic temperatures of ultrafine-grained Ti-6Al-4V alloy processed by ECAP

Abstract

This research is focused on a study of the relationship between mechanical behavior, microstructure and fracture toughness of a Ti-6Al-4V alloy in both coarse-grained (CG) and ultrafine-grained (UFG) conditions. The UFG state with a primary alpha-phase grain size, but with different orientations with respect to the testing direction, was produced by equal-channel angular pressing (ECAP) after thermo-mechanical treatment. Fracture toughness and mechanical testing were conducted at a temperature of 196 °C. A duplex UFG structure formation in the Ti-6Al-4V alloy led to an enhancement of yield stress and a decrease in the fracture toughness at 196 С by comparison with the CG alloy. The lowest values of fracture toughness were observed in a sample in which there were elongated grains lying parallel to the loading direction during testing compared to the situation where the grains were perpendicular to this direction. The reasons for the reduction in fracture toughness in the UFG Ti alloy are discussed.

Characterization of the Microstructure, Local Macro-Texture and Residual Stress Field of Commercially Pure Titanium Grade 2 Prepared by CONFORM ECAP

“…In the last two decades, many studies have appeared on the topic of ECAP processed titanium alloys. All investigations agreed that the ECAP method led to an ultra-fine grained (UFG) microstructure and enhanced strength [3][4][5][6][7][8].…”

“…The center of the 2D PSD was set to a fixed value 2θD = 55° during the experiments. This 2θD angle allowed the observation of reflections (101 ̅ 1) and (0002), and the nominal gauge volume (NGV) was ~32.96 mm 3 .…”

Structural evolution in a synthetically produced ultrafine grained low carbon steel

“…Majority of researchers have aimed at evolving newer means to reproducibly manufacture second phase strengthened nanograined steels and as well as, gaining insight into the underlying physical sciences. Continued effort to tailor strategy for toughening and strengthening of ultra fine grained steels encompasses employment of different processing routes like thermomechanical processing [5,6], severe plastic deformation by equal channel angular pressing [7,8], cyclic quenching [9], dynamic strain induced transformation [10][11][12], roll bonding [13,14], bidirectional large scale deformation and dynamic recrystallization through multi axle forging [15][16][17] for the production of ultra fine grained steels. These processes enable to achieve excellent combination of strength and ductility; accordingly, structurally refined steels of various types are seen to have assumed considerable commercial importance [18].…”

Microstructure and Failure Characteristics of Nanostructured Molybdenum–Copper Composites

“…Especially in the last 10 years, the fracture behavior of ultrafine-grained (UFG) and nanocrystalline (NC) metals processed by SPD techniques has come to the center of experimental interest in several research groups. [8][9][10][11][12][13][14][15] It was found that UFG and NC metals show a wide spectrum of fracture properties depending on factors such as the testing orientation, extent of SPD deformation, and temperature. The need to test different orientations in SPDprocessed materials, which are essential for materials exhibiting pronounced grain aspect ratios, showcased the ability to obtain one of the highest levels of damage tolerance, achievable in technically relevant metallic alloys.…”