An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The ...An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200–1100°C/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.展开更多
Semicontinuous equal-channel angular extrusion（ SC-ECAE） is a novel severe plastic deformation technique that has been developed to produce ultrafine-grain steels. Instead of external forces being exerted on specime...Semicontinuous equal-channel angular extrusion（ SC-ECAE） is a novel severe plastic deformation technique that has been developed to produce ultrafine-grain steels. Instead of external forces being exerted on specimens in the conventional ECAE,driving forces are applied to dies in SC-EACE. The deformation of interstitial-free（ IF） steel w as performed at room temperature,and individual specimens w ere repeatedly processed at various passes. An overall grain size of 0. 55 μm w as achieved after 10 passes. During SC-ECAE,the main textures of IF steel included { 111} ,{ 110} ,{ 112} ,{ 110} ,and { 110} At an early stage,increasing dislocations induce new textures and increase intensity. When the deformation continues,low-angle boundaries are formed betw een dislocation cell bands,w hich cause some dislocation cell bands to change their orientation,and therefore,the intensity of the textures begins to decrease. After more passes,the intensity of textures continues to decrease w ith high-angle boundaries,and the sub-grains in dislocation cell bands continuously increase. The present study reports the evolution of textures during deformation; these w ere examined and characterized using high-resolution electron backscattered diffraction（ EBSD） in a field emission scanning electron microscope. The mechanisms of texture evolution are discussed.展开更多
Approximately half of plastic waste ends up in landfills,where fragmentation leads to the leakage of microplastics,nanoplastics,and petrogenic carbon back into ecosystems.However,the timeframe for plastic re-entry int...Approximately half of plastic waste ends up in landfills,where fragmentation leads to the leakage of microplastics,nanoplastics,and petrogenic carbon back into ecosystems.However,the timeframe for plastic re-entry into the geological carbon cycle remains unknown.Using landfill-derived field data,we developed a model predicting fragmentation of various polymers into macroplastics,microplastics,fine microplastics,and nanoplastics.We find total waste plastic concentrations range from 85 to 414 mg g^(-1),with microplastic,fine microplastic,and nanoplastic generation rates of 2–69,0.5–36.8,and 0.04–1.9 mg per g of plastic,respectively.Plastic distribution depends more on landfill depth than disposal age.Polyethylene terephthalate fragments faster than polypropylene or polyethylene.Our model predicts peak microplastic and fine microplastic fractions within 157–382 and 412–2118 years,respectively,with approximately half of the plastic-derived carbon available for geological cycling in 80–208 years.This research helps clarify the environmental fate of pervasive plastic pollution.展开更多
Crystal orientation governs the plasticity of intermetallic alloys,yet the atomicscale mechanisms linking defect dynamics to mechanical properties remain elusive.Here,we unveil unprecedented deformation pathways in si...Crystal orientation governs the plasticity of intermetallic alloys,yet the atomicscale mechanisms linking defect dynamics to mechanical properties remain elusive.Here,we unveil unprecedented deformation pathways in single-crystal γ-TiAl through largescale molecular dynamics simulations under uniaxial tension across four crystallographic orientations:[100],[112],[110],and[111].Strikingly,a metastable body-centered cubic(BCC)phase emerges transiently during[100]-oriented stretching,acting as a critical bridge between elastic and plastic regimes—a phenomenon unreported in γ-TiAl.For[110]and[111]orientations,we identify a hierarchical defect evolution cascade(intrinsic stacking faults→extrinsic stacking faults→twin boundary(ISF→ESF→TB))driven by intersecting stacking faults and Shockley partial dislocation interactions,which govern twin boundary nucleation and growth.In contrast,[112]-oriented deformation adheres to conventional dislocation-mediated plasticity.These findings reveal how crystallographic anisotropy dictates defect dynamics,offering atomic-scale insights into deformation twinning and transient phase transitions.This work bridges atomistic processes to macroscopic properties,advancing the design of next-generation lightweight hightemperature materials.展开更多
基金the research board of the Sharif University of Technology for financial support and the provision of the research facilities used in this work
文摘An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200–1100°C/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.
文摘Semicontinuous equal-channel angular extrusion（ SC-ECAE） is a novel severe plastic deformation technique that has been developed to produce ultrafine-grain steels. Instead of external forces being exerted on specimens in the conventional ECAE,driving forces are applied to dies in SC-EACE. The deformation of interstitial-free（ IF） steel w as performed at room temperature,and individual specimens w ere repeatedly processed at various passes. An overall grain size of 0. 55 μm w as achieved after 10 passes. During SC-ECAE,the main textures of IF steel included { 111} ,{ 110} ,{ 112} ,{ 110} ,and { 110} At an early stage,increasing dislocations induce new textures and increase intensity. When the deformation continues,low-angle boundaries are formed betw een dislocation cell bands,w hich cause some dislocation cell bands to change their orientation,and therefore,the intensity of the textures begins to decrease. After more passes,the intensity of textures continues to decrease w ith high-angle boundaries,and the sub-grains in dislocation cell bands continuously increase. The present study reports the evolution of textures during deformation; these w ere examined and characterized using high-resolution electron backscattered diffraction（ EBSD） in a field emission scanning electron microscope. The mechanisms of texture evolution are discussed.
基金financially supported by the National Natural Science Foundation of China(22276140)。
文摘Approximately half of plastic waste ends up in landfills,where fragmentation leads to the leakage of microplastics,nanoplastics,and petrogenic carbon back into ecosystems.However,the timeframe for plastic re-entry into the geological carbon cycle remains unknown.Using landfill-derived field data,we developed a model predicting fragmentation of various polymers into macroplastics,microplastics,fine microplastics,and nanoplastics.We find total waste plastic concentrations range from 85 to 414 mg g^(-1),with microplastic,fine microplastic,and nanoplastic generation rates of 2–69,0.5–36.8,and 0.04–1.9 mg per g of plastic,respectively.Plastic distribution depends more on landfill depth than disposal age.Polyethylene terephthalate fragments faster than polypropylene or polyethylene.Our model predicts peak microplastic and fine microplastic fractions within 157–382 and 412–2118 years,respectively,with approximately half of the plastic-derived carbon available for geological cycling in 80–208 years.This research helps clarify the environmental fate of pervasive plastic pollution.
基金financial support by the National Science and Technology Major Project(No.2025ZD0618600)the General Projects for Key Industrial Chain Technology Research and Development of Xi'an(No.24ZDCYJSGG0050)the Key Technology Project of Ningbo"Science and Technology Innovation Yongjiang 2035"(No.2024Z155).
文摘Crystal orientation governs the plasticity of intermetallic alloys,yet the atomicscale mechanisms linking defect dynamics to mechanical properties remain elusive.Here,we unveil unprecedented deformation pathways in single-crystal γ-TiAl through largescale molecular dynamics simulations under uniaxial tension across four crystallographic orientations:[100],[112],[110],and[111].Strikingly,a metastable body-centered cubic(BCC)phase emerges transiently during[100]-oriented stretching,acting as a critical bridge between elastic and plastic regimes—a phenomenon unreported in γ-TiAl.For[110]and[111]orientations,we identify a hierarchical defect evolution cascade(intrinsic stacking faults→extrinsic stacking faults→twin boundary(ISF→ESF→TB))driven by intersecting stacking faults and Shockley partial dislocation interactions,which govern twin boundary nucleation and growth.In contrast,[112]-oriented deformation adheres to conventional dislocation-mediated plasticity.These findings reveal how crystallographic anisotropy dictates defect dynamics,offering atomic-scale insights into deformation twinning and transient phase transitions.This work bridges atomistic processes to macroscopic properties,advancing the design of next-generation lightweight hightemperature materials.
