Increasingly harsh service conditions place higher requirements for the high strain-rate performance of titanium alloys.Adiabatic shear band(ASB),a phenomenon prone to dynamic loading,is often accom-panied by catastro...Increasingly harsh service conditions place higher requirements for the high strain-rate performance of titanium alloys.Adiabatic shear band(ASB),a phenomenon prone to dynamic loading,is often accom-panied by catastrophic damage.Yet,it is unclear how the internal nanostructures are related to shear instability.Here we report detailed microstructural evolution in the ASB of a titanium alloy via in-depth focused ion beam(FIB),transmission Kikuchi diffraction(TKD),and high-resolution transmission electron microscope(HRTEM)analyses,with the deformation instability phenomenon discussed from the energy perspective.The ASB interior undergoes multifaceted changes,namely deformation-induced beta-to-alpha transformation and deformation-induced martensitic transformation to form substantially refined and heterogeneous structures.Meanwhile,two types of extremely fine twins are identified to occur within both nano-sized martensite and alpha phase.The critical plastic work representing the onset of adiabatic shear instability and dynamic equilibrium is observed to be constant for a specific structure in the same deformation mode.The energy analysis could be extended to other materials subjected to high strain-rate dynamic deformation.展开更多
The interaction between{112}<111>deformation twinning and grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair miso...The interaction between{112}<111>deformation twinning and grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair misorientation angles(MA)and geometric compatibility factor(m’).Generally,in the coaxial polycrystal,the value of MA determines the occurrence of twin transfer(TT)or twin blockage(TB),i.e.,twin transfer occurs at MA≤29°with twin blockage otherwise.Under TT,the value of m’affects the selection of twin variants.,i.e.,the twin system with a larger m’is easier to active.The morphology of twin pairs is ruler-shaped and lenticular under TT and TB,respectively,with different thickening mechanisms,including grain boundary dislocation emission.展开更多
The rapidly increasing scientific interest in 3D-printed high-entropy alloys(HEAs)necessitates the understanding of their deformation mechanisms.Here,we present the grain rotation behavior of a nearly equiatomic CrMnF...The rapidly increasing scientific interest in 3D-printed high-entropy alloys(HEAs)necessitates the understanding of their deformation mechanisms.Here,we present the grain rotation behavior of a nearly equiatomic CrMnFeCoNi HEA fabricated with laser-beam powder bed fusion via quasi in-situ electron backscatter diffraction(EBSD)observations during compressive deformation.The rotation paths of grains can be predicted via a new lattice reorientation factor(m_(A)),defined as the average of primary and secondary slip Schmid factors.The grains that initially have their〈111〉directions oriented close to the loading direction with low-to-intermediate m_(A)values tend to rotate towards the〈101〉pole.The grains initially oriented in the center of inverse pole figures with high m_(A)values develop multiple rotation paths pointing away from the〈001〉pole.The cube-oriented grains with their〈001〉directions close to the loading direction undergo face-centered cubic(FCC)-to-hexagonal close-packed(HCP)phase transformation due to the activation of octahedral slip involving multiple slip systems.This transformation can be well elucidated via a modified parameter,defined as the average of four maximum Schmid factors on each of four{111}slip/twinning planes in FCC crystals.The findings provide new insights into the underlying mechanisms for deformation-induced grain rotation and phase transformation,and help pave the way for developing advanced HEAs via transformation-induced plasticity.展开更多
基金supported by the National Natural Science Foundation of China (NSFC) (Nos.51871168,52271012)the Natural Sciences and Engineering Research Council of Canada (NSERC)in the form of international research collaboration.Q.C.,A.H.F.,and S.J.Q.are grateful to the Southwest Institute of Technology and Engineering Cooperation Fund (No.HDHDW5902020102)H.W.acknowledges the financial support of the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact (No.6142902220301).
文摘Increasingly harsh service conditions place higher requirements for the high strain-rate performance of titanium alloys.Adiabatic shear band(ASB),a phenomenon prone to dynamic loading,is often accom-panied by catastrophic damage.Yet,it is unclear how the internal nanostructures are related to shear instability.Here we report detailed microstructural evolution in the ASB of a titanium alloy via in-depth focused ion beam(FIB),transmission Kikuchi diffraction(TKD),and high-resolution transmission electron microscope(HRTEM)analyses,with the deformation instability phenomenon discussed from the energy perspective.The ASB interior undergoes multifaceted changes,namely deformation-induced beta-to-alpha transformation and deformation-induced martensitic transformation to form substantially refined and heterogeneous structures.Meanwhile,two types of extremely fine twins are identified to occur within both nano-sized martensite and alpha phase.The critical plastic work representing the onset of adiabatic shear instability and dynamic equilibrium is observed to be constant for a specific structure in the same deformation mode.The energy analysis could be extended to other materials subjected to high strain-rate dynamic deformation.
基金financially supported by the Key-Area Re-search and Development Program of GuangDong Province(No.2019B010941001)National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(No.6142902220301)+1 种基金Shanghai Engineering Research Center of High-Performance Medical Device Materials(No.20DZ2255500)the Major Science and Technology Infrastructure Project of Material Genome Bigscience Facilities Platform supported by Municipal Development and Reform Commission of Shenzhen.
文摘The interaction between{112}<111>deformation twinning and grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair misorientation angles(MA)and geometric compatibility factor(m’).Generally,in the coaxial polycrystal,the value of MA determines the occurrence of twin transfer(TT)or twin blockage(TB),i.e.,twin transfer occurs at MA≤29°with twin blockage otherwise.Under TT,the value of m’affects the selection of twin variants.,i.e.,the twin system with a larger m’is easier to active.The morphology of twin pairs is ruler-shaped and lenticular under TT and TB,respectively,with different thickening mechanisms,including grain boundary dislocation emission.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC),Natural Resources Canada(NRCan),Alberta Innovates,and the National Natural Science Foundation of China(NSFC)(Grant Nos.52271012 and 51871168)for the financial support.
文摘The rapidly increasing scientific interest in 3D-printed high-entropy alloys(HEAs)necessitates the understanding of their deformation mechanisms.Here,we present the grain rotation behavior of a nearly equiatomic CrMnFeCoNi HEA fabricated with laser-beam powder bed fusion via quasi in-situ electron backscatter diffraction(EBSD)observations during compressive deformation.The rotation paths of grains can be predicted via a new lattice reorientation factor(m_(A)),defined as the average of primary and secondary slip Schmid factors.The grains that initially have their〈111〉directions oriented close to the loading direction with low-to-intermediate m_(A)values tend to rotate towards the〈101〉pole.The grains initially oriented in the center of inverse pole figures with high m_(A)values develop multiple rotation paths pointing away from the〈001〉pole.The cube-oriented grains with their〈001〉directions close to the loading direction undergo face-centered cubic(FCC)-to-hexagonal close-packed(HCP)phase transformation due to the activation of octahedral slip involving multiple slip systems.This transformation can be well elucidated via a modified parameter,defined as the average of four maximum Schmid factors on each of four{111}slip/twinning planes in FCC crystals.The findings provide new insights into the underlying mechanisms for deformation-induced grain rotation and phase transformation,and help pave the way for developing advanced HEAs via transformation-induced plasticity.
