Shock compression and spallation damage of a face-center cubic phase high-entropy alloy(HEA)Al_(0.1)CoCrFeNi were investigated via plate impact experiments along with free surface velocity measurements.Postmortem samp...Shock compression and spallation damage of a face-center cubic phase high-entropy alloy(HEA)Al_(0.1)CoCrFeNi were investigated via plate impact experiments along with free surface velocity measurements.Postmortem samples were characterized with transmission electron microscopy and electron backscatter diffraction.The Hugoniot equation of state and spall strength at different impact strengths were determined.There exists a power-law relation between spall strength and strain rate.The spall strength of Al_(0.1)CoCrFeNi HEA is about 50%higher than those of previously studied HEAs and comparable to those widely applied structural stainless steels at the same shock stress.Dislocation glide and stacking faults are the important deformation mechanisms in the Al_(0.1)CoCrFeNi HEA.Nanotwins are only observed at high shock stress.Damage in the Al_(0.1)CoCrFeNi HEA is ductile in nature.Voids are nucleated preferentially in grain interiors,and the intragranular voids show a strong dependence on grain boundary misorientation and peak stress.展开更多
Multiple ballistic impacts are carried out on a 2024-T4 aluminum alloy by spherical steel projectiles(5-mm diameter)at~400 m s^(-1),to investigate its dynamic deformation and damage.The ballistic impact process is cap...Multiple ballistic impacts are carried out on a 2024-T4 aluminum alloy by spherical steel projectiles(5-mm diameter)at~400 m s^(-1),to investigate its dynamic deformation and damage.The ballistic impact process is captured with high-speed photography.Postmortem samples are characterized with optical imaging,three-dimensional laser scanning,microhardness testing and electron backscatter diffraction.With increasing number of impacts,crater diameter increases slightly,but crater depth and crater volume increase significantly,and strain accumulation leads to microhardness increase overall.Crater parameters all follow power-law relations with the number of impacts.Twin-like deformation bands and macroscopic deformation twins are produced by impact as a result of spontaneous dislocation self-pinning under high strain rate,large shear deformation.Under multiple impacts,shear strain accumulation in the arc-shaped region of the crater induces deformation twinning when it exceeds a critical value(~1.1-1.6).It is highly possible that the deformation twins are related to deformation bands,since they both share one set of the{111}pole with the initial matrix grain.A finite element method model is optimized to reproduce experimental observations and interpret deformation mechanisms.展开更多
Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is in-vestigated.Active{1121}and{1012}extension twinning is observed.The activation of{1121}twinning in a certain grain is inf...Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is in-vestigated.Active{1121}and{1012}extension twinning is observed.The activation of{1121}twinning in a certain grain is influenced not only by its own Schmid factor,but also by that of the basal slip.Twin-twin interactions of the co-zone{1121}twin variants are commonly observed and systematically studied,including the crystallographic characteristics of the four typically observed twin-twin junctions(TTJs)and the associated twin-twin boundaries.Unlike the quilted-looking TTJs formed by the interaction of co-zone{1012}twin variants,crossing-like TTJs of co-zone{1121}twin variants are observed and their formation mechanisms are discussed.Crossing-like TTJs are also formed by the interaction of{1121}and{10¯12}twins.The morphology and thickening rate of{1121}and{1012}twins vary markedly due to the difference in twinning shear.The needle-like{1121}twins thicken more slowly than the lenticular{1012}twins.Twin nucleation is observed on the previously formed{1121}twin boundary due to the relatively large strain concentration on such interface,while twin nucleation on{1012}twin boundary is rarely observed.展开更多
Shock compression and spallation of a eutectic high-entropy alloy(HEA)AlCoCrFeNi_(2.1)with lamellar structure are investigated via plate impact loading with free-surface velocity measurements.The as-cast and postmorte...Shock compression and spallation of a eutectic high-entropy alloy(HEA)AlCoCrFeNi_(2.1)with lamellar structure are investigated via plate impact loading with free-surface velocity measurements.The as-cast and postmortem samples are characterized with transmission electron microscopy,electron back-scatter diffraction and scanning electron microscopy.An accurate Hugoniot equation of state is determined.Af-ter shock compression to∼12 GPa,both the L1_(2)and B_(2)phases retain their ordered structures.Dense dislocations in the{111}slip planes,stacking faults and deformation twins are found in the L1_(2)phase,along with fewer dislocations in the{110}slip bands in the B(2)phase.Shock-induced deformation twin-ning within the L1_(2)phase of this HEA is observed as a new deformation mechanism under various load-ing conditions.For spallation,both ductile and brittle damage modes are observed.The micro voids and cracks prefer to nucleate at the phase boundaries chiefly,then in the B(2)phase.Under similar shock stress,the spall strength of AlCoCrFeNi_(2.1)HEA is about 40%higher than those of other reported dual-phase HEAs due to the high stability of its semi-coherent phase boundaries.展开更多
基金financially supported in part by the Sichuan Province Key R&D Program(No.2022YFG0033)the National Natural Science Foundation of China(Nos.11627901 and11902274)。
文摘Shock compression and spallation damage of a face-center cubic phase high-entropy alloy(HEA)Al_(0.1)CoCrFeNi were investigated via plate impact experiments along with free surface velocity measurements.Postmortem samples were characterized with transmission electron microscopy and electron backscatter diffraction.The Hugoniot equation of state and spall strength at different impact strengths were determined.There exists a power-law relation between spall strength and strain rate.The spall strength of Al_(0.1)CoCrFeNi HEA is about 50%higher than those of previously studied HEAs and comparable to those widely applied structural stainless steels at the same shock stress.Dislocation glide and stacking faults are the important deformation mechanisms in the Al_(0.1)CoCrFeNi HEA.Nanotwins are only observed at high shock stress.Damage in the Al_(0.1)CoCrFeNi HEA is ductile in nature.Voids are nucleated preferentially in grain interiors,and the intragranular voids show a strong dependence on grain boundary misorientation and peak stress.
基金supported by the Scientific Challenge Project of China(Grant No.TZ2018001)the National Natural Science Foundation of China(Grant Nos.11627901,11802252)the Science and Technology Program of Sichuan Province(Grant No.2020YFG0415)。
文摘Multiple ballistic impacts are carried out on a 2024-T4 aluminum alloy by spherical steel projectiles(5-mm diameter)at~400 m s^(-1),to investigate its dynamic deformation and damage.The ballistic impact process is captured with high-speed photography.Postmortem samples are characterized with optical imaging,three-dimensional laser scanning,microhardness testing and electron backscatter diffraction.With increasing number of impacts,crater diameter increases slightly,but crater depth and crater volume increase significantly,and strain accumulation leads to microhardness increase overall.Crater parameters all follow power-law relations with the number of impacts.Twin-like deformation bands and macroscopic deformation twins are produced by impact as a result of spontaneous dislocation self-pinning under high strain rate,large shear deformation.Under multiple impacts,shear strain accumulation in the arc-shaped region of the crater induces deformation twinning when it exceeds a critical value(~1.1-1.6).It is highly possible that the deformation twins are related to deformation bands,since they both share one set of the{111}pole with the initial matrix grain.A finite element method model is optimized to reproduce experimental observations and interpret deformation mechanisms.
基金sponsored in part by the National Natural Sci-ence Foundation of China (No.52101150)the Sichuan Science and Technology Program (No.2022YFG0287)the Fundamental Re-search Funds for the Central Universities (No.2682021CX114).
文摘Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is in-vestigated.Active{1121}and{1012}extension twinning is observed.The activation of{1121}twinning in a certain grain is influenced not only by its own Schmid factor,but also by that of the basal slip.Twin-twin interactions of the co-zone{1121}twin variants are commonly observed and systematically studied,including the crystallographic characteristics of the four typically observed twin-twin junctions(TTJs)and the associated twin-twin boundaries.Unlike the quilted-looking TTJs formed by the interaction of co-zone{1012}twin variants,crossing-like TTJs of co-zone{1121}twin variants are observed and their formation mechanisms are discussed.Crossing-like TTJs are also formed by the interaction of{1121}and{10¯12}twins.The morphology and thickening rate of{1121}and{1012}twins vary markedly due to the difference in twinning shear.The needle-like{1121}twins thicken more slowly than the lenticular{1012}twins.Twin nucleation is observed on the previously formed{1121}twin boundary due to the relatively large strain concentration on such interface,while twin nucleation on{1012}twin boundary is rarely observed.
基金sponsored in part by Sichuan Province Key R&D Program(No.2022YFG0033)the National Natural Science Foundation of China(Nos.12102491,52101150,11902274,11627901).
文摘Shock compression and spallation of a eutectic high-entropy alloy(HEA)AlCoCrFeNi_(2.1)with lamellar structure are investigated via plate impact loading with free-surface velocity measurements.The as-cast and postmortem samples are characterized with transmission electron microscopy,electron back-scatter diffraction and scanning electron microscopy.An accurate Hugoniot equation of state is determined.Af-ter shock compression to∼12 GPa,both the L1_(2)and B_(2)phases retain their ordered structures.Dense dislocations in the{111}slip planes,stacking faults and deformation twins are found in the L1_(2)phase,along with fewer dislocations in the{110}slip bands in the B(2)phase.Shock-induced deformation twin-ning within the L1_(2)phase of this HEA is observed as a new deformation mechanism under various load-ing conditions.For spallation,both ductile and brittle damage modes are observed.The micro voids and cracks prefer to nucleate at the phase boundaries chiefly,then in the B(2)phase.Under similar shock stress,the spall strength of AlCoCrFeNi_(2.1)HEA is about 40%higher than those of other reported dual-phase HEAs due to the high stability of its semi-coherent phase boundaries.
