“…Finally, the green marked boundary is newly formed during multiple twinning and becomes the special GB with a misorientation angle of 142.38° at both sides. Previous research also mentioned the all possible angles for the newly formed special GB produced by two or three twinning events in Mg alloy 21 , the angle of the special GB for the two twinning (TBI + TBII) is very similar to the present case.Figure 6Formation of the secondary tensile twins inside the primary compressive twins. The deformation patterns are collected at strains of ( a ) 3%; ( b ) 4%.…”
Section: Resultssupporting
confidence: 76%
“…These pre-existing twins will play very important roles in the following tensile deformation, contributing to the strengthening all way to very small TBS and to strain hardening by interactions between dislocations and TBs and phase transformation. More importantly, multiple twinning could be formed during subsequent tensile deformation, which plays a key role for strengthening and strain hardening in the plastic deformation for hcp metals with low SFE 21, 32 . Overall, four different deformation mechanisms are observed in the NC cobalt with lamellar compressive/tensile twins, and these consistent mechanisms with decreasing TBS will contribute to the strengthening and the strain hardening in such a way as discussed in following: (i) Additional TBs for pre-existing lamellar twins should pose extra energy barriers for the basal partial dislocations to overcome, which is very similar to the TB strengthening in fcc metals.…”
Section: Discussionmentioning
confidence: 99%
“…In contrast, twinning is an important mechanism for plastic deformation of CG hcp metals in addition to dislocation slip due to their relatively limited slip systems when compared to fcc metals 19 . Theoretically, at least seven twinning modes involving different twinning planes can be existing in hcp metals, such as {}, {}, {}, {}, {}, {}, {} twins 20, 21 . Among them, {} and {} twins (usually referred to tensile twins and compressive twins) are the most common twinning modes in hcp metals and alloys 22, 23 , which can be easily observed in the zone axis under TEM.…”
Section: Introductionmentioning
confidence: 99%
“…Annealing twins have also been observed in pure cobalt during the electroplated process or the annealing process 24, 25 . Recently, multiple twinning has been found to play a key role in the plastic deformation and the grain refinement of hcp metals and alloys 21, 32 .…”
Twins play an important role in the deformation of nanocrystalline (NC) metals. The size effects of {} tensile/{} compressive lamellar twins on the tensile strength and deformation mechanisms of NC hcp cobalt have been investigated by a series of large-scale molecular dynamics simulations. Unlike the size effects of twins on the strength for polycrystalline fcc metals, the strength of NC hcp cobalt with lamellar tensile/compressive twins monotonically increases with decreasing twin boundary spacing (TBS) and no softening stage is observed, which is due to the consistent deformation mechanisms no matter TBS is large or small. These consistent deformation mechanisms can be categorized into four types of strengthening mechanisms: (i) Partial basal dislocations nucleated from grain boundaries (GBs) or twin boundaries (TBs) intersecting with TBs/GBs; (ii) Phase transformation from hcp to fcc; (iii) partial edge dislocations nucleated from TBs intersecting with basal partial dislocations; (iv) Growth of the newly formed secondary tensile twins inside the primary compressive/tensile twins. The observed multiple twinning in MD simulations has also been confirmed by TEM after tensile testing in NC cobalt processed by severe plastic deformation.
“…Finally, the green marked boundary is newly formed during multiple twinning and becomes the special GB with a misorientation angle of 142.38° at both sides. Previous research also mentioned the all possible angles for the newly formed special GB produced by two or three twinning events in Mg alloy 21 , the angle of the special GB for the two twinning (TBI + TBII) is very similar to the present case.Figure 6Formation of the secondary tensile twins inside the primary compressive twins. The deformation patterns are collected at strains of ( a ) 3%; ( b ) 4%.…”
Section: Resultssupporting
confidence: 76%
“…These pre-existing twins will play very important roles in the following tensile deformation, contributing to the strengthening all way to very small TBS and to strain hardening by interactions between dislocations and TBs and phase transformation. More importantly, multiple twinning could be formed during subsequent tensile deformation, which plays a key role for strengthening and strain hardening in the plastic deformation for hcp metals with low SFE 21, 32 . Overall, four different deformation mechanisms are observed in the NC cobalt with lamellar compressive/tensile twins, and these consistent mechanisms with decreasing TBS will contribute to the strengthening and the strain hardening in such a way as discussed in following: (i) Additional TBs for pre-existing lamellar twins should pose extra energy barriers for the basal partial dislocations to overcome, which is very similar to the TB strengthening in fcc metals.…”
Section: Discussionmentioning
confidence: 99%
“…In contrast, twinning is an important mechanism for plastic deformation of CG hcp metals in addition to dislocation slip due to their relatively limited slip systems when compared to fcc metals 19 . Theoretically, at least seven twinning modes involving different twinning planes can be existing in hcp metals, such as {}, {}, {}, {}, {}, {}, {} twins 20, 21 . Among them, {} and {} twins (usually referred to tensile twins and compressive twins) are the most common twinning modes in hcp metals and alloys 22, 23 , which can be easily observed in the zone axis under TEM.…”
Section: Introductionmentioning
confidence: 99%
“…Annealing twins have also been observed in pure cobalt during the electroplated process or the annealing process 24, 25 . Recently, multiple twinning has been found to play a key role in the plastic deformation and the grain refinement of hcp metals and alloys 21, 32 .…”
Twins play an important role in the deformation of nanocrystalline (NC) metals. The size effects of {} tensile/{} compressive lamellar twins on the tensile strength and deformation mechanisms of NC hcp cobalt have been investigated by a series of large-scale molecular dynamics simulations. Unlike the size effects of twins on the strength for polycrystalline fcc metals, the strength of NC hcp cobalt with lamellar tensile/compressive twins monotonically increases with decreasing twin boundary spacing (TBS) and no softening stage is observed, which is due to the consistent deformation mechanisms no matter TBS is large or small. These consistent deformation mechanisms can be categorized into four types of strengthening mechanisms: (i) Partial basal dislocations nucleated from grain boundaries (GBs) or twin boundaries (TBs) intersecting with TBs/GBs; (ii) Phase transformation from hcp to fcc; (iii) partial edge dislocations nucleated from TBs intersecting with basal partial dislocations; (iv) Growth of the newly formed secondary tensile twins inside the primary compressive/tensile twins. The observed multiple twinning in MD simulations has also been confirmed by TEM after tensile testing in NC cobalt processed by severe plastic deformation.
“…Suzuki [10] reported that solute atoms were easy to segregate to SFs, and this prediction has been later experimentally confirmed [11][12][13]. Such segregation stabilizes SF configurations and dramatically pins dislocation motion, which leads to further strengthening [14].…”
The different segregation and lattice structure in the sample edge layer (SEL) of Mg–Gd–TM (TM: solute element, mainly Ni or Ag) alloys prepared by ion thinner have been investigated in this study. The result displays that the polycrystalline phase, Mg2GdNi9, is found in the SEL zone of Mg–Gd–Ni alloys, and the single‐crystalline phase, MgGdAg2, is found in the SEL zone of Mg–Gd–Ag alloys. The investigation of different lattice structures contributes to the distinguishment and analysis of the illusionary phases in the SEL zone of Mg–Gd–TM ternary alloys by electron microscopy sampling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
