It is extremely difficult to introduce high-density nano twins during the solidification process of TiAl alloy.In this study,high-density nanotwins are inducted in the as-cast Ti48Al2Cr alloyed by adding Re element.Ph...It is extremely difficult to introduce high-density nano twins during the solidification process of TiAl alloy.In this study,high-density nanotwins are inducted in the as-cast Ti48Al2Cr alloyed by adding Re element.Phase transformation,morphology characteristics of nano twins,compressive and tensile proper-ties,and the related mechanisms have been studied.Results show that B2 phase enriched with Re tends to precipitate along theα_(2)/γinterface within lamellar colony.The stacking fault energy(SFE)ofγphase decreases from 43 mJ/m^(2) to 16 mJ/m^(2) as Re content increases from 0 at.%to 0.6 at.%,decreasing the crit-ical shear stress for twin formation.Compared to the mismatch value ofα_(2)/γinterface(0.004),which of B2/α_(2) and B2/γinterfaces increase to 0.247 and 0.149,respectively.Driven by high interfacial stress,high-density dislocations are generated at the B2/α_(2) interface,providing the dislocation slip channel for the formation of stacking faults(SFs)and nanotwins at the B2/γinterface.Therefore,the mechanism of inducting high-density nanotwins is to reduce the stacking fault energy ofγphase by Re and form highly mismatched B2/α_(2) interface.Compressive strength and the strain increase from 1723 MPa to 2398 MPa and 29%to 39%as Re content increases from 0 at.%to 0.6 at.%,respectively.Tensile strength increases from 356 MPa to 452 MPa without sacrificing plasticity.The improvement in strength and plasticity are attributed to the nano-twinning strengthening and interfacial thermal mismatch strengthening.Forming nanotwins during solidification process serve as the nucleation sites for newly formed twins during de-formation process,increasing the deformation tolerance of TiAl alloy.展开更多
Tailoring high-density annealing twins in laser powder bed fusion(LPBF)-fabricated alloys based on their intrinsic residual stress requires high annealing temperatures and/or long-term annealing,result-ing in the abno...Tailoring high-density annealing twins in laser powder bed fusion(LPBF)-fabricated alloys based on their intrinsic residual stress requires high annealing temperatures and/or long-term annealing,result-ing in the abnormal growth of large recrystallized grains,which is detrimental to mechanical properties.This work proposes a new strategy for achieving a favorable strength-plasticity synergy of the LPBF-fabricated Inconel 718 superalloy by performing a deep cryogenic treatment(DCT)with the subsequent heat treatment(including annealing and double aging)to tailor fine grains with“high-density annealing twins+precipitates”architectures and compares the obtained material with an alloy subjected to a direct heat treatment without a prior DCT.The obtained results reveal that the additional internal stress gen-erated during DCT increases the stored energy and dislocation density,which provide a sufficient driving force for activating high-density annealing twin boundaries(63.2%)with fine grains(31.6μm)within a short annealing time.The more homogeneous tailored microstructure with the“finer grains+high-density twins+precipitates”architectures decreases the mean free path of slipping dislocations,pro-moting intensive interactions with dislocations and inducing a strong strain hardening effect.The mul-tiple deformation modes of stacking faults coupled with Lomer-Cottrell locks,thin primary deformation twins,and secondary twins activated during tensile loading,sustaining a strong work hardening ability and delaying the plastic instability,which exhibits a high strength(yield strength of 1088 MPa and tensile strength of 1369 MPa)and excellent plasticity(elongation of 30%).This work not only describes a fea-sible method for simultaneously enhancing the strength and plasticity in additively manufactured(AM)alloys but also provides new insights into increasing the fraction of twins at a small grain size to improve the grain boundary-related properties without destroying the AM alloy shape.展开更多
Conversation is an essential component of virtual avatar activities in the metaverse.With the development of natural language processing,significant breakthroughs have been made in text and voice conversation generati...Conversation is an essential component of virtual avatar activities in the metaverse.With the development of natural language processing,significant breakthroughs have been made in text and voice conversation generation.However,face-to-face conversations account for the vast majority of daily conversations,while most existing methods focused on single-person talking head generation.In this work,we take a step further and consider generating realistic face-to-face conversation videos.Conversation generation is more challenging than single-person talking head generation,because it requires not only the generation of photo-realistic individual talking heads,but also the listener’s response to the speaker.In this paper,we propose a novel unified framework based on the neural radiance field(NeRF)to address these challenges.Specifically,we model both the speaker and the listener with a NeRF framework under different conditions to control individual expressions.The speaker is driven by the audio signal,while the response of the listener depends on both visual and acoustic information.In this way,face-to-face conversation videos are generated between human avatars,with all the interlocutors modeled within the same network.Moreover,to facilitate future research on this task,we also collected a new human conversation dataset containing 34 video clips.Quantitative and qualitative experiments evaluate our method in different aspects,e.g.,image quality,pose sequence trend,and natural rendering of the scene in the generated videos.Experimental results demonstrate that the avatars in the resulting videos are able to carry on a realistic conversation,and maintain individual styles.展开更多
基金supported by the National Natural Science Foundation of China(No.U21A2042)the National Nature Fund Youth Fund Project of China(No.52101038)Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001).
文摘It is extremely difficult to introduce high-density nano twins during the solidification process of TiAl alloy.In this study,high-density nanotwins are inducted in the as-cast Ti48Al2Cr alloyed by adding Re element.Phase transformation,morphology characteristics of nano twins,compressive and tensile proper-ties,and the related mechanisms have been studied.Results show that B2 phase enriched with Re tends to precipitate along theα_(2)/γinterface within lamellar colony.The stacking fault energy(SFE)ofγphase decreases from 43 mJ/m^(2) to 16 mJ/m^(2) as Re content increases from 0 at.%to 0.6 at.%,decreasing the crit-ical shear stress for twin formation.Compared to the mismatch value ofα_(2)/γinterface(0.004),which of B2/α_(2) and B2/γinterfaces increase to 0.247 and 0.149,respectively.Driven by high interfacial stress,high-density dislocations are generated at the B2/α_(2) interface,providing the dislocation slip channel for the formation of stacking faults(SFs)and nanotwins at the B2/γinterface.Therefore,the mechanism of inducting high-density nanotwins is to reduce the stacking fault energy ofγphase by Re and form highly mismatched B2/α_(2) interface.Compressive strength and the strain increase from 1723 MPa to 2398 MPa and 29%to 39%as Re content increases from 0 at.%to 0.6 at.%,respectively.Tensile strength increases from 356 MPa to 452 MPa without sacrificing plasticity.The improvement in strength and plasticity are attributed to the nano-twinning strengthening and interfacial thermal mismatch strengthening.Forming nanotwins during solidification process serve as the nucleation sites for newly formed twins during de-formation process,increasing the deformation tolerance of TiAl alloy.
基金This work was funded by the Program for Industry Support of University in Gansu Province(No.2023CYZC-28)Major Science and Technology Projects of Gansu Province(No.22ZD6GA008)+2 种基金Key Research and Development Program of Gansu Province(No.22YF7GA156)Science Foundation for Youths of Gansu Province(No.23JRRA772)the Hong Liu First-class Discipline Construc-tion Plan of Lanzhou University of Technology.
文摘Tailoring high-density annealing twins in laser powder bed fusion(LPBF)-fabricated alloys based on their intrinsic residual stress requires high annealing temperatures and/or long-term annealing,result-ing in the abnormal growth of large recrystallized grains,which is detrimental to mechanical properties.This work proposes a new strategy for achieving a favorable strength-plasticity synergy of the LPBF-fabricated Inconel 718 superalloy by performing a deep cryogenic treatment(DCT)with the subsequent heat treatment(including annealing and double aging)to tailor fine grains with“high-density annealing twins+precipitates”architectures and compares the obtained material with an alloy subjected to a direct heat treatment without a prior DCT.The obtained results reveal that the additional internal stress gen-erated during DCT increases the stored energy and dislocation density,which provide a sufficient driving force for activating high-density annealing twin boundaries(63.2%)with fine grains(31.6μm)within a short annealing time.The more homogeneous tailored microstructure with the“finer grains+high-density twins+precipitates”architectures decreases the mean free path of slipping dislocations,pro-moting intensive interactions with dislocations and inducing a strong strain hardening effect.The mul-tiple deformation modes of stacking faults coupled with Lomer-Cottrell locks,thin primary deformation twins,and secondary twins activated during tensile loading,sustaining a strong work hardening ability and delaying the plastic instability,which exhibits a high strength(yield strength of 1088 MPa and tensile strength of 1369 MPa)and excellent plasticity(elongation of 30%).This work not only describes a fea-sible method for simultaneously enhancing the strength and plasticity in additively manufactured(AM)alloys but also provides new insights into increasing the fraction of twins at a small grain size to improve the grain boundary-related properties without destroying the AM alloy shape.
基金supported by the National Natural Science Foundation of China(Nos.62201342 and 62101325)Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0102).
文摘Conversation is an essential component of virtual avatar activities in the metaverse.With the development of natural language processing,significant breakthroughs have been made in text and voice conversation generation.However,face-to-face conversations account for the vast majority of daily conversations,while most existing methods focused on single-person talking head generation.In this work,we take a step further and consider generating realistic face-to-face conversation videos.Conversation generation is more challenging than single-person talking head generation,because it requires not only the generation of photo-realistic individual talking heads,but also the listener’s response to the speaker.In this paper,we propose a novel unified framework based on the neural radiance field(NeRF)to address these challenges.Specifically,we model both the speaker and the listener with a NeRF framework under different conditions to control individual expressions.The speaker is driven by the audio signal,while the response of the listener depends on both visual and acoustic information.In this way,face-to-face conversation videos are generated between human avatars,with all the interlocutors modeled within the same network.Moreover,to facilitate future research on this task,we also collected a new human conversation dataset containing 34 video clips.Quantitative and qualitative experiments evaluate our method in different aspects,e.g.,image quality,pose sequence trend,and natural rendering of the scene in the generated videos.Experimental results demonstrate that the avatars in the resulting videos are able to carry on a realistic conversation,and maintain individual styles.
