As one of the fundamental outcomes of dislocation self-interaction,dislocation dipoles have an important influence on the plastic deformation of materials,especially on fatigue and creep.In this work,superdislocation ...As one of the fundamental outcomes of dislocation self-interaction,dislocation dipoles have an important influence on the plastic deformation of materials,especially on fatigue and creep.In this work,superdislocation dipoles inγ-TiAl andα_(2)-Ti_(3)Al were systematically investigated by atomistic simulations,with a variety of dipole heights,orientations and annealing tempe ratures.The results indicate that non-screw super-dipoles transform into locally stable dipolar or reconstructed cores at low temperature,while into isolated or interconnected point defect clusters and stacking fault tetrahedra at high temperature via short-range diffu sion.Non-screw super-dipoles inγ-TiAl andα_(2)-Ti_(3)Al exhibit similar features as fcc and hcp metals,respectively.Generally,over long-term annealing where diffusion is significant,60°superdipoles inγ-TiAl are stable,whereas the stability of super-dipoles inα2-Ti3 Al increases with dipole height and orientation angle.The influence on mechanical properties can be well evaluated by integrating these results into mesoscale or constitutive models.展开更多
The mechanical response of a single crystal titanium sample against(0001)α surface impact was investigated using molecular dynamics simulation.Remarkably,non-uniform plastic deformation was observed in the sample.At ...The mechanical response of a single crystal titanium sample against(0001)α surface impact was investigated using molecular dynamics simulation.Remarkably,non-uniform plastic deformation was observed in the sample.At high strain rates,amorphization occurred near the edge of the contact region where severe shear strain induced a large number of stacking faults(SFs)and dislocations.In contrast,the central part of the contact region underwent less deformation with significantly fewer dislocations.Moreover,instead of amorphization by consuming SFs and dislocations,there was a gradual increase in the density of dislocations and SFs during the process of amorphization.These local amorphous regions eventually grew into shear bands.展开更多
基金the National Key Research and Development Program of China(No.2016YFB0701304 and 2017YFB0306201)the Natural Science Foundation of China(Nos.51671195 and 91960202)+4 种基金the Frontier and Key Projects of the Chinese Academy of Sciences(Nos.QYZDJ-SSW-JSC031-01 and XXH13506-304)the Natural Science Foundation of Liaoning(No.20180510032)the Aeronautical Science Foundation of China(No.20160292002)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDC01000000)The Project is sponsored by the“Liaoning BaiQianWan”Talents Program。
文摘As one of the fundamental outcomes of dislocation self-interaction,dislocation dipoles have an important influence on the plastic deformation of materials,especially on fatigue and creep.In this work,superdislocation dipoles inγ-TiAl andα_(2)-Ti_(3)Al were systematically investigated by atomistic simulations,with a variety of dipole heights,orientations and annealing tempe ratures.The results indicate that non-screw super-dipoles transform into locally stable dipolar or reconstructed cores at low temperature,while into isolated or interconnected point defect clusters and stacking fault tetrahedra at high temperature via short-range diffu sion.Non-screw super-dipoles inγ-TiAl andα_(2)-Ti_(3)Al exhibit similar features as fcc and hcp metals,respectively.Generally,over long-term annealing where diffusion is significant,60°superdipoles inγ-TiAl are stable,whereas the stability of super-dipoles inα2-Ti3 Al increases with dipole height and orientation angle.The influence on mechanical properties can be well evaluated by integrating these results into mesoscale or constitutive models.
基金the National Natural Science Foundation of China(U2241245,91960202 and 52271012)the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(6142902220301)+2 种基金the Aeronautical Science Foundation of China(2022Z053092001)the Shanghai Engineering Research Center of High-Performance Medical Device Materials(20DZ2255500)the Opening Project of National Key Laboratory of Shock Wave and Detonation Physics(2022JCJQLB05702).
文摘The mechanical response of a single crystal titanium sample against(0001)α surface impact was investigated using molecular dynamics simulation.Remarkably,non-uniform plastic deformation was observed in the sample.At high strain rates,amorphization occurred near the edge of the contact region where severe shear strain induced a large number of stacking faults(SFs)and dislocations.In contrast,the central part of the contact region underwent less deformation with significantly fewer dislocations.Moreover,instead of amorphization by consuming SFs and dislocations,there was a gradual increase in the density of dislocations and SFs during the process of amorphization.These local amorphous regions eventually grew into shear bands.
