Recrystallization stands as an essential process that influences the microstructure and properties of magnesium(Mg)alloys,yet its mechanisms remain complex and multifaceted.This review explores the key factors affecti...Recrystallization stands as an essential process that influences the microstructure and properties of magnesium(Mg)alloys,yet its mechanisms remain complex and multifaceted.This review explores the key factors affecting the recrystallization behavior of Mg alloys,emphasizing how their unique structural characteristics impact the driving forces and dynamics of recrystallization.Unlike conventional alloys,Mg alloys exhibit distinctive recrystallization kinetics,which is significantly affected by deformation conditions,such as strain rate,temperature,and processing methods(e.g.,rolling,forging,and extrusion).The process is also influenced by material characteristics,including initial grain size,texture,dislocation density,solute clustering,and stacking fault energy.Additionally,uneven strain distribution,stress concentrations,and stored energy play crucial roles in shaping the formation of recrystallized grains,particularly near grain boundaries.Notably,recrystallization is driven by dislocation accumulation and the availability of slip systems,with new strain-free grains typically forming in regions of high dislocation density.This paper synthesizes the existing literature to provide a comprehensive understanding of the mechanisms and kinetics of recrystallization in Mg alloys,highlighting the influence of microstructural features such as second-phase particles and grain boundary characteristics.It also identifies key challenges and suggests promising directions for future research,including optimizing material compositions and the interaction between deformation conditions via machine learning.展开更多
Precipitation via thermal treatments is among the most effective approaches to strengthening and is widely applied in the Al industry. Thermal treatments combined with deformation are capable of finely regulating the ...Precipitation via thermal treatments is among the most effective approaches to strengthening and is widely applied in the Al industry. Thermal treatments combined with deformation are capable of finely regulating the process of precipitation and distribution of precipitates. Deformation-induced defects exert significant impacts on the precipitation and already present precipitates, which however is often overlooked. In this study, the interactions between deformation and precipitation/precipitates, and their impacts on mechanical properties were systematically investigated in the solution-treated (ST) Al-0.61Mg-1.17Si-0.5Cu (wt.%), processed by multi-pass equal channel angular pressing (ECAP) and thermal treatments. Novel deformation-mediated cyclic evolution of precipitates is discovered: ST→ (1,2 passes: deformation induced precipitation) Guinier Preston (GP) zones→ (An250/30) Q’ and L phases→ (3-pass: deformation induced fragmentation/resolution) spherical precipitates→ (4-pass: deformation induced further fragmentation/resolution) GP zones. On this basis, we extend the quasi-binary phase diagram of Al-Mg_(2)Si along deformation as the third dimension and construct an innovative defect phase diagram for the Al-Mg-Si-based system. To testify to the effect of deformation-mediated cyclic evolution of precipitation/precipitates on the optimum mechanical properties, peak-aging treatments were performed in samples of ST and 3-pass states. Based on the microscopic characterizations, a distinctive mechanism of peak-aging strengthening is proposed. Notably in the 3-pass ECAPed and peak-aged sample the dominant strengthening phases become the L precipitates that thrived from the segmented and spherical L phases, rather than β’’ precipitates in the solely peak-aged ST sample. Our work provides a feasible example for exploring the combined processing technique of multi-step deformation and thermal treatments, to optimize the mechanical properties.展开更多
High temperature performance of magnesium alloys can be tailored by either grain size or precipitates in the grain interior.In this study,exceptional creep resistance was successfully acquired in a RE-free cast Mg-Al-...High temperature performance of magnesium alloys can be tailored by either grain size or precipitates in the grain interior.In this study,exceptional creep resistance was successfully acquired in a RE-free cast Mg-Al-Ca-Ti(AC51Ti)alloy.Microalloying of Ti(0.01 wt.%)has been found to be beneficial to the improvement of the tensile creep resistance in a RE-free cast Mg-5Al-0.35Mn-(1Ca)(AC51)alloy,showing a low state creep rate(SCR)of 2.70×10^(−9)s^(−1)at 200℃/50 MPa,which is even better than that of many reported RE-containing Mg alloys.The presence of trace Ti contributes to the substantial refinement and more uniform distribution of Al_(2)Ca precipitates in the matrix.At the same time,the microalloying of Ti improves the solubility of Al and Ca in the matrix.It is reasonable to believe that the microalloying of Ti induced re-organization of Al_(2)Ca precipitates,dissolved a larger amount of Al and Ca atoms into magnesium lattice,and increased the possibility of interaction between GB/dislocations and precipitates,which strongly correlates with the high temperature properties.The creep strengthening mechanisms primarily attributed to both second phase strengthening and solid solution strengthening were separately proposed based on the experimental investigations.展开更多
Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic rec...Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic recrystallization(DRX),while twin regions experience rapid recrystallization during static recrystallization(SRX).The activation of twinning can lead to changes in lattice orientation,significantly impacting the final texture in Mg alloys.The active roles of twinning are influenced by various factors during the activation process,and the mobility of twin boundaries(TB)can be amplified by stress effects,dislocation interactions,and thermal effects.Conversely,annealing treatments that involve proper segregation or precipitation on TBs serve to stabilize them,restraining their motion.Events such as segregation may also alter the twinning propensity in Magnesium-rare earth(Mg-RE)alloys.While{10–11}contraction twins(CT)and{10–11}-{10–12}double twins(DT)can promote dynamic recrystallization(DRX),they also pose a risk as potential sources of voids and cracks.Additionally,understanding the nucleation and growth mechanisms of twinning is crucial,and these aspects are briefly reviewed in this article.Considering the factors mentioned above,this article summarizes the recent research progress in this field,shedding light on advancements in recent eras.展开更多
Due to their unique precipitation behavior,magnesium-rare earth(Mg-RE)alloys exhibit excellent strength and high thermal stability.However,owing to the negative blocking effect of precipitation on dislocation slipping...Due to their unique precipitation behavior,magnesium-rare earth(Mg-RE)alloys exhibit excellent strength and high thermal stability.However,owing to the negative blocking effect of precipitation on dislocation slipping,the plasticity and ductility of Mg-RE alloys become deteriorate after aging treatment.In this work,a novel strategy to improve the combination of strength and ductility by designing a laminate heterostructured Mg alloy is proposed.High-pressure torsion(HPT)processing is employed to fabricate a clean and well-bonded interface between MgGdYAg and MgAg alloys.The two alloys have huge differences in precipitation hardening,and ductility is improved due to two facts.For one thing,the density of the second phases in the MgAg alloy is much lower than that of MgGdYAg alloy;for another,the non-basal〈c+a〉slipping is continuously activated during deformation.Through this mechanism,the uniform elongation of the heterostructured MgAg/MgGdYAg/MgAg alloy is improved to 7.1%.展开更多
In this work,mechanical alloying of the alternating stacked pure Al and Zn thin foils was accomplished via high-pressure torsion(HPT).In the alloyed Al-Zn system,an exotic phase transformation from hexagonal close-pac...In this work,mechanical alloying of the alternating stacked pure Al and Zn thin foils was accomplished via high-pressure torsion(HPT).In the alloyed Al-Zn system,an exotic phase transformation from hexagonal close-packed(HCP)to face-centered cubic(FCC)was identified.The atomic-scale evolution process and underlying mechanism of phase transformation down to atomic scale are provided by molecular dynamics simulation and high-resolution transmission electron microscopy.The HCP→FCC phase transformation was attributed to the sliding of Shockley partial dislocations generated at the Al-Zn grain boundaries,which resulted in an[2110][011]and(0001)/(111)orientation relationship between the two phases.This work provides a new approach for the in-depth study of the solid phase transformation of Al-Zn alloys and also shed lights on understanding the mechanical properties of the HPT processed Al-Zn alloys.展开更多
基金funding by the National Natural Science Foundation of China(Grant number U22A20187)(Grant No.52271147,No.52471175)China Postdoctoral Science Foundation(grant number 2024M751172)。
文摘Recrystallization stands as an essential process that influences the microstructure and properties of magnesium(Mg)alloys,yet its mechanisms remain complex and multifaceted.This review explores the key factors affecting the recrystallization behavior of Mg alloys,emphasizing how their unique structural characteristics impact the driving forces and dynamics of recrystallization.Unlike conventional alloys,Mg alloys exhibit distinctive recrystallization kinetics,which is significantly affected by deformation conditions,such as strain rate,temperature,and processing methods(e.g.,rolling,forging,and extrusion).The process is also influenced by material characteristics,including initial grain size,texture,dislocation density,solute clustering,and stacking fault energy.Additionally,uneven strain distribution,stress concentrations,and stored energy play crucial roles in shaping the formation of recrystallized grains,particularly near grain boundaries.Notably,recrystallization is driven by dislocation accumulation and the availability of slip systems,with new strain-free grains typically forming in regions of high dislocation density.This paper synthesizes the existing literature to provide a comprehensive understanding of the mechanisms and kinetics of recrystallization in Mg alloys,highlighting the influence of microstructural features such as second-phase particles and grain boundary characteristics.It also identifies key challenges and suggests promising directions for future research,including optimizing material compositions and the interaction between deformation conditions via machine learning.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22A20187,52171007,52371111,and 52371177).
文摘Precipitation via thermal treatments is among the most effective approaches to strengthening and is widely applied in the Al industry. Thermal treatments combined with deformation are capable of finely regulating the process of precipitation and distribution of precipitates. Deformation-induced defects exert significant impacts on the precipitation and already present precipitates, which however is often overlooked. In this study, the interactions between deformation and precipitation/precipitates, and their impacts on mechanical properties were systematically investigated in the solution-treated (ST) Al-0.61Mg-1.17Si-0.5Cu (wt.%), processed by multi-pass equal channel angular pressing (ECAP) and thermal treatments. Novel deformation-mediated cyclic evolution of precipitates is discovered: ST→ (1,2 passes: deformation induced precipitation) Guinier Preston (GP) zones→ (An250/30) Q’ and L phases→ (3-pass: deformation induced fragmentation/resolution) spherical precipitates→ (4-pass: deformation induced further fragmentation/resolution) GP zones. On this basis, we extend the quasi-binary phase diagram of Al-Mg_(2)Si along deformation as the third dimension and construct an innovative defect phase diagram for the Al-Mg-Si-based system. To testify to the effect of deformation-mediated cyclic evolution of precipitation/precipitates on the optimum mechanical properties, peak-aging treatments were performed in samples of ST and 3-pass states. Based on the microscopic characterizations, a distinctive mechanism of peak-aging strengthening is proposed. Notably in the 3-pass ECAPed and peak-aged sample the dominant strengthening phases become the L precipitates that thrived from the segmented and spherical L phases, rather than β’’ precipitates in the solely peak-aged ST sample. Our work provides a feasible example for exploring the combined processing technique of multi-step deformation and thermal treatments, to optimize the mechanical properties.
基金funded by the National Natural Science Foundation of China(Grant numbers U22A20187,52374405,52371177).
文摘High temperature performance of magnesium alloys can be tailored by either grain size or precipitates in the grain interior.In this study,exceptional creep resistance was successfully acquired in a RE-free cast Mg-Al-Ca-Ti(AC51Ti)alloy.Microalloying of Ti(0.01 wt.%)has been found to be beneficial to the improvement of the tensile creep resistance in a RE-free cast Mg-5Al-0.35Mn-(1Ca)(AC51)alloy,showing a low state creep rate(SCR)of 2.70×10^(−9)s^(−1)at 200℃/50 MPa,which is even better than that of many reported RE-containing Mg alloys.The presence of trace Ti contributes to the substantial refinement and more uniform distribution of Al_(2)Ca precipitates in the matrix.At the same time,the microalloying of Ti improves the solubility of Al and Ca in the matrix.It is reasonable to believe that the microalloying of Ti induced re-organization of Al_(2)Ca precipitates,dissolved a larger amount of Al and Ca atoms into magnesium lattice,and increased the possibility of interaction between GB/dislocations and precipitates,which strongly correlates with the high temperature properties.The creep strengthening mechanisms primarily attributed to both second phase strengthening and solid solution strengthening were separately proposed based on the experimental investigations.
基金supported by the National Natural Science Foundation of China(No.U22A20187,No.52271147,No.12261160364).
文摘Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic recrystallization(DRX),while twin regions experience rapid recrystallization during static recrystallization(SRX).The activation of twinning can lead to changes in lattice orientation,significantly impacting the final texture in Mg alloys.The active roles of twinning are influenced by various factors during the activation process,and the mobility of twin boundaries(TB)can be amplified by stress effects,dislocation interactions,and thermal effects.Conversely,annealing treatments that involve proper segregation or precipitation on TBs serve to stabilize them,restraining their motion.Events such as segregation may also alter the twinning propensity in Magnesium-rare earth(Mg-RE)alloys.While{10–11}contraction twins(CT)and{10–11}-{10–12}double twins(DT)can promote dynamic recrystallization(DRX),they also pose a risk as potential sources of voids and cracks.Additionally,understanding the nucleation and growth mechanisms of twinning is crucial,and these aspects are briefly reviewed in this article.Considering the factors mentioned above,this article summarizes the recent research progress in this field,shedding light on advancements in recent eras.
基金supported by the Key Program of National Natural Science Foundation of China(No.51931003)the National Natural Science Foundation of China(Nos.52171118 and 52201124 and U22A20187)+4 种基金the China Postdoctoral Science Foundation(No.2021M701715)the Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2022ZB279)the Project Internationalized Construction of Teachers of Jiangsu University(NO.4023000059)the Projects in Science and Technique Plans of Ningbo City(No.2019B10083)the Opening Project of the Key Laboratory of Advanced Manufacturing and Intelligent Technology(Ministry of Education)of Harbin University of Science and Technology(No.KFKT202103).
文摘Due to their unique precipitation behavior,magnesium-rare earth(Mg-RE)alloys exhibit excellent strength and high thermal stability.However,owing to the negative blocking effect of precipitation on dislocation slipping,the plasticity and ductility of Mg-RE alloys become deteriorate after aging treatment.In this work,a novel strategy to improve the combination of strength and ductility by designing a laminate heterostructured Mg alloy is proposed.High-pressure torsion(HPT)processing is employed to fabricate a clean and well-bonded interface between MgGdYAg and MgAg alloys.The two alloys have huge differences in precipitation hardening,and ductility is improved due to two facts.For one thing,the density of the second phases in the MgAg alloy is much lower than that of MgGdYAg alloy;for another,the non-basal〈c+a〉slipping is continuously activated during deformation.Through this mechanism,the uniform elongation of the heterostructured MgAg/MgGdYAg/MgAg alloy is improved to 7.1%.
基金funded by the National Natural Science Foundation of China(Grant Nos.51905215,U22A20187)the Major Scientific and Technological Innovation Project of Shandong Province of China(Grant No.2019JZZY020111).
文摘In this work,mechanical alloying of the alternating stacked pure Al and Zn thin foils was accomplished via high-pressure torsion(HPT).In the alloyed Al-Zn system,an exotic phase transformation from hexagonal close-packed(HCP)to face-centered cubic(FCC)was identified.The atomic-scale evolution process and underlying mechanism of phase transformation down to atomic scale are provided by molecular dynamics simulation and high-resolution transmission electron microscopy.The HCP→FCC phase transformation was attributed to the sliding of Shockley partial dislocations generated at the Al-Zn grain boundaries,which resulted in an[2110][011]and(0001)/(111)orientation relationship between the two phases.This work provides a new approach for the in-depth study of the solid phase transformation of Al-Zn alloys and also shed lights on understanding the mechanical properties of the HPT processed Al-Zn alloys.
