In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-prin...In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-principal element alloys (MPEAs). The present atomistic simulations on single crystals revealthat during the deformation of CrCoNi, stress gradients lead to the formation of novel inverse disloca-tion pileup. We find that this unique dislocation pattern in a confined volume is due to the elevatedlattice friction and significant stress gradient present in the material. Furthermore, this phenomenon canbe notably promoted by lowering the temperature, increasing the loading rate, and introducing chemicalshort-range ordering. Additional simulations on bicrystals show that these inverse pileups play a criticalrole in suppressing dislocation transmission, reflection, and grain boundary (GB) migration. As a result,they effectively mitigate stress concentration and reduce damage accumulation at GBs, lowering the riskof catastrophic failure due to GB damages. In our theoretical analysis, we utilize dislocation mechanics topredict the formation of the inverse pileup and its subsequent strengthening effect, considering scenarioswith and without obstacles. Our investigations encompass various lattice frictions and stress gradients.Remarkably, our results shed light on the prevailing impact of dislocation hardening in the plastic de-formation of CrCoNi even under the presence of a linear stress gradient, while the contribution of GBstrengthening is found to be comparatively limited. These findings provide valuable insights into the de-formation mechanisms of MPEAs in general and significantly aid their applications as promising structuralmaterials.展开更多
The combination of ultrahigh strength and excellent ductility of nanotwinned materials is rooted in the interaction between dislocations and twin boundaries(TBs).Quantifying the interaction between TBs and dislocation...The combination of ultrahigh strength and excellent ductility of nanotwinned materials is rooted in the interaction between dislocations and twin boundaries(TBs).Quantifying the interaction between TBs and dislocations not only offers fresh perspectives of designing materials with high strength and ductility,but also becomes the cornerstone of multiscale modeling of materials with TBs.In this work,an atomcontinuum coupling model was adopted to quantitatively investigate the interaction between dislocations and TBs.The simulation shows that the dislocation-TB interaction is much weaker than the interaction between dislocations at the same distance.Simulation of the early stage of dislocation pileups further verifies that the experimentally observed repulsive forces are essentially from the dislocations or kink-like steps on TBs.The interaction between TBs and dislocations with different Burgers vectors was demonstrated referring to the elastic theory of dislocations.With the intrinsic interaction between dislocations and TBs being clarified,this work will promote further development of the multiscale simulation methods,such as discrete dislocation dynamics or phase-field method,of materials with TBs by providing a quantitative description of the interactions between TBs and dislocations.展开更多
文摘In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-principal element alloys (MPEAs). The present atomistic simulations on single crystals revealthat during the deformation of CrCoNi, stress gradients lead to the formation of novel inverse disloca-tion pileup. We find that this unique dislocation pattern in a confined volume is due to the elevatedlattice friction and significant stress gradient present in the material. Furthermore, this phenomenon canbe notably promoted by lowering the temperature, increasing the loading rate, and introducing chemicalshort-range ordering. Additional simulations on bicrystals show that these inverse pileups play a criticalrole in suppressing dislocation transmission, reflection, and grain boundary (GB) migration. As a result,they effectively mitigate stress concentration and reduce damage accumulation at GBs, lowering the riskof catastrophic failure due to GB damages. In our theoretical analysis, we utilize dislocation mechanics topredict the formation of the inverse pileup and its subsequent strengthening effect, considering scenarioswith and without obstacles. Our investigations encompass various lattice frictions and stress gradients.Remarkably, our results shed light on the prevailing impact of dislocation hardening in the plastic de-formation of CrCoNi even under the presence of a linear stress gradient, while the contribution of GBstrengthening is found to be comparatively limited. These findings provide valuable insights into the de-formation mechanisms of MPEAs in general and significantly aid their applications as promising structuralmaterials.
基金financially supported by the Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project(Grant No.HZQB-KCZYB-2020030)the National Natural Science Foundation of China(Grant Nos.12072062,11772082,12072061)+2 种基金the Liaoning Revitalization Talents Program(Grant No.XLYC1807193)Key Research and Development Project of Liaoning Province(Grant No.2020JH2/10500003)the Fundamental Research Funds for the Central Universities(Grant No.DUT20LAB203)。
文摘The combination of ultrahigh strength and excellent ductility of nanotwinned materials is rooted in the interaction between dislocations and twin boundaries(TBs).Quantifying the interaction between TBs and dislocations not only offers fresh perspectives of designing materials with high strength and ductility,but also becomes the cornerstone of multiscale modeling of materials with TBs.In this work,an atomcontinuum coupling model was adopted to quantitatively investigate the interaction between dislocations and TBs.The simulation shows that the dislocation-TB interaction is much weaker than the interaction between dislocations at the same distance.Simulation of the early stage of dislocation pileups further verifies that the experimentally observed repulsive forces are essentially from the dislocations or kink-like steps on TBs.The interaction between TBs and dislocations with different Burgers vectors was demonstrated referring to the elastic theory of dislocations.With the intrinsic interaction between dislocations and TBs being clarified,this work will promote further development of the multiscale simulation methods,such as discrete dislocation dynamics or phase-field method,of materials with TBs by providing a quantitative description of the interactions between TBs and dislocations.
