Varying tensile fracture mechanisms of Cu and Cu–Zn alloys with reduced grain size: From necking to shearing instability

Influence of annealing on stain hardening behaviour and fracture properties of a cryorolled Al 2014 alloy

“…Such microstructure cannot effectively store dislocations and they promote shear localisation, P a g e 15 | leading to nucleation of numerous shear bands [27][28][29]. As a result, the material fails instantly after the onset of plastic instability and undergoes minimal amount of necking.…”

“…[27] has also specified that for nanocrysalline grains shearing is the dominant fracture mechanism and with increase in grain size fracture takes place via both necking and shear localisation. As a result, during tensile loading, fracture is initiated rapidly from these multiple sites resulting in catastrophic failure.…”

Strength, damage and fracture behaviors of high-nitrogen austenitic stainless steel processed by high-pressure torsion

“…Firstly, the defects including dislocations, grain boundaries, twin boundaries and their mutual interactions may effectively strengthen the materials. For the present HNS steel processed by HPT for 1/16, 1/4, 1 and 5 turns, the slip stress in the interior of grains increases so that the critical shear stress s 0 along the localized shear bands is greatly enhanced [23]. Secondly, there is also an enhanced propensity for damage because these defects, 260 due to the significant increase of abundant and highly mobile vacancies, may, for example, agglomerate or form some pore-and crack-like defects.…”

“…The dynamic recovery rate of dislocations prevents dislocation boundaries from accumulating on smaller scales [22]. These changes in the microstructure can restrict the effect of shearing instability on the failure of materials, resulting in the material having a higher strength [23]. The structure evolution and grain refinement mechanisms are similar to those of several intensively studied 316L austenitic steels 170 [24,25].…”

“…The specimens processed through 1/16, 1/4, 1 and 5 turns rup-200 tured by shearing at different shear angles of 48°, 50°, 60°a nd 72°, respectively, as revealed by further inspection. In recent reports on a Cu-Ag alloy processed by HPT and three Cu-Zn alloys processed by ECAP [23,26], the specimens macroscopically also failed through shear fracture at angles >45°. All these phenomena exhibit similarities to bulk metallic glasses (BMGs) during tensile testing [27] where the specimens generally fail in a shear fracture mode with shear angles >45°.…”