scholarly journals The Plastic Deformation Mechanisms of hcp Single Crystals with Different Orientations: Molecular Dynamics Simulations

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 733
Author(s):  
Zhi-Chao Ma ◽  
Xiao-Zhi Tang ◽  
Yong Mao ◽  
Ya-Fang Guo
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Phase Transformation ◽  
Molecular Dynamics Simulations ◽  
Single Crystals ◽  
Deformation Mechanisms ◽  
Shear Stresses ◽  
Affecting Factors ◽  
Fcc Phase ◽  
Dynamics Simulations

The deformation mechanisms of Mg, Zr, and Ti single crystals with different orientations are systematically studied by using molecular dynamics simulations. The affecting factors for the plasticity of hexagonal close-packed (hcp) metals are investigated. The results show that the basal <a> dislocation, prismatic <a> dislocation, and pyramidal <c + a> dislocation are activated in Mg, Zr, and Ti single crystals. The prior slip system is determined by the combined effect of the Schmid factor and the critical resolved shear stresses (CRSS). Twinning plays a crucial role during plastic deformation since basal and prismatic slips are limited. The 101¯2 twinning is popularly observed in Mg, Zr, and Ti due to its low CRSS. The 101¯1 twin appears in Mg and Ti, but not in Zr because of the high CRSS. The stress-induced hcp-fcc phase transformation occurs in Ti, which is achieved by successive glide of Shockley partial dislocations on basal planes. More types of plastic deformation mechanisms (including the cross-slip, double twins, and hcp-fcc phase transformation) are activated in Ti than in Mg and Zr. Multiple deformation mechanisms coordinate with each other, resulting in the higher strength and good ductility of Ti. The simulation results agree well with the related experimental observation.

scholarly journals A Molecular Dynamics Simulations Study of the Influence of Prestrain on the Pop-In Behavior and Indentation Size Effect in Cu Single Crystals

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5220
Author(s):  
Rongguang Xu ◽  
Hengxu Song ◽  
Yongsheng Leng ◽  
Stefanos Papanikolaou
Keyword(s):  
Molecular Dynamics ◽  
Residual Stresses ◽  
Size Effect ◽  
Molecular Dynamics Simulations ◽  
Single Crystals ◽  
Mechanical Response ◽  
Indentation Size Effect ◽  
Deformation Mechanisms ◽  
Indentation Size ◽  
Dynamics Simulations

The pop-in effect in nanoindentation of metals represents a major collective dislocation phenomenon that displays sensitivity in the local surface microstructure and residual stresses. To understand the deformation mechanisms behind pop-ins in metals, large scale molecular dynamics simulations are performed to investigate the pop-in behavior and indentation size effect in undeformed and deformed Cu single crystals. Tensile loading, unloading, and reloading simulations are performed to create a series of samples subjected to a broad range of tensile strains with/without pre-existing dislocations. The subsequent nanoindentation simulations are conducted to investigate the coupled effects of prestrain and the presence of resulting dislocations and surface morphology, as well as indenter size effects on the mechanical response in indentation processes. Our work provides detailed insights into the deformation mechanisms and microstructure-property relationships of nanoindentation in the presence of residual stresses and strains.

scholarly journals A Molecular Dynamics Simulations Study of the Influence of Prestrain on the Pop-in Behavior and Indentation Size Effect in Cu Single Crystals

2021 ◽  
Author(s):  
Rong-Guang Xu ◽  
Hengxu Song ◽  
Yongsheng Leng ◽  
Stefanos Papanikolaou
Keyword(s):  
Molecular Dynamics ◽  
Residual Stresses ◽  
Size Effect ◽  
Molecular Dynamics Simulations ◽  
Single Crystals ◽  
Mechanical Response ◽  
Indentation Size Effect ◽  
Deformation Mechanisms ◽  
Indentation Size ◽  
Dynamics Simulations

The pop-in effect in nanoindentation of metals represents a major collective dislocation phenome-non that displays sensitivity in the local surface microstructure and residual stresses. To under-stand the deformation mechanisms behind pop-ins in metals, large scale molecular dynamics simulations are carried out to investigate the pop-in behavior and indentation size effect in unde-formed and deformed Cu single crystals. Tensile loading, unloading and reloading simulations are performed to create a series of samples subjected to a broad range of tensile strains with/without pre-existing dislocations. The subsequent nanoindentation simulations are con-ducted to study the coupled effects of pre-strain, the presence of resulting dislocations and surface morphology, as well as indenter size effects on the mechanical response in indentation processes. Our work provides detailed insights into the deformation mechanisms and microstruc-ture-property relationships of nanoindentation in the presence of residual stresses and strains.

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