Rare-earth(RE) magnesium alloys have attracted lots of attention due to their excellent mechanical properties.In this work,the microstructure and mechanical properties of as-extruded 8.5Gd-4.5Y-0.8Zn-0.4Zr magnesium a...Rare-earth(RE) magnesium alloys have attracted lots of attention due to their excellent mechanical properties.In this work,the microstructure and mechanical properties of as-extruded 8.5Gd-4.5Y-0.8Zn-0.4Zr magnesium alloy under different solution treatment were examined with the optical microscope(OM),scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM),electron back-scattered diffraction(EBSD) and Instron testing machine.The results show that the ES12alloy(solution treatment for 12 h at 520℃) has the highest ultimate tensile strength(UTS) of 390 MPa with a fracture elongation of 24.5% at the co st of a minor drop in yielding strength(YS) compared to the asextruded alloy.During solution treatment,the block-shaped long period stacking ordered(LPSO) in asextruded alloy evolves into plate-shaped LPSO,which disperses at grain boundaries(GBs),and lamellar LPSO,which distributes in grains.The coexistence of plate-shaped and lamellar LPSO,which impedes the dislocations movement,and the activated dislocations are regarded as the primary reasons for mechanical properties improvement.Furthermore,the(11-21) <1-100> texture in as-extruded alloy transforms into the(11-20) <0001> texture in ES12 alloy.The average grain size increases from 3.45 μm in as-extruded alloy to 18.70 μm in ES12 alloy.The Schmid factors of {0001} <11-20>,{10-10} <11-20>,{10-11} <11-20>,and {11-22} <11-23> increase,which indicate that slip systems are more easily activated in plastic deformation.The dynamic recrystallization(DRX) grains fraction increase to 92.8% for ES12 alloy due to the particle-stimulated nucleation(PSN) mechanism triggered by block-shaped and plate-shaped LPSO.The freshly DRXed grains further weaken the texture,and reduce the dislocation density.All of these factors increase elongation of RE magnesium alloy.展开更多
The homogenized Mg−5.6Gd−0.8Zn(wt.%)alloys were treated with water cooling and furnace cooling to obtain specimens without and with the 14H long-period stacking ordered(LPSO)phase.Subsequently,multi-directional forgin...The homogenized Mg−5.6Gd−0.8Zn(wt.%)alloys were treated with water cooling and furnace cooling to obtain specimens without and with the 14H long-period stacking ordered(LPSO)phase.Subsequently,multi-directional forging(MDF)experiments were carried out.The microstructure and mechanical properties of different regions(the center,middle and edge regions)in the MDFed alloys were systematically investigated,and the effect of LPSO phase on them was discussed.The results show that the alloys in different regions undergo significant grain refinement during the MDF process.Inhomogeneous microstructures with different degrees of dynamic recrystallization(DRX)are formed,resulting in microhardness heterogeneity.The alloy with the LPSO phase has higher microstructure homogeneity,a higher degree of recrystallization,and better comprehensive mechanical properties than the alloy without the LPSO phase.The furnace-cooled alloy after 18 passes of MDF has the best comprehensive mechanical properties,with an ultimate compressive strength of 488 MPa,yield strength of 258 MPa,and fracture strain of 21.2%.DRX behavior is closely related to the LPSO phase and deformation temperature.The kinked LPSO phase can act as a potential nucleation site for DRX grains,while the fragmented LPSO phase promotes DRX nucleation through the particle-stimulated nucleation mechanism.展开更多
Suitable heat treatment processes were adopted to regulate the precipitation of the lamellar LPSO phase andβ′phase in Mg−Gd−Y−Zn−Zr−Nd alloy.The effects of lamellar LPSO phase andβ′phase on the mechanical properti...Suitable heat treatment processes were adopted to regulate the precipitation of the lamellar LPSO phase andβ′phase in Mg−Gd−Y−Zn−Zr−Nd alloy.The effects of lamellar LPSO phase andβ′phase on the mechanical properties and damping capacity of the alloy were studied systematically.Experimental results demonstrate that the lamellar LPSO phase is more conducive to dynamic recrystallization processes,leading to a high degree of recrystallization and a weak texture intensity,resulting in a higher plasticity and damping capacity.After aging treatment,theβ′precipitates exhibit pronounced aging strengthening and increase the number of mobile interfaces,thus enhancing the strength and damping capacity at the same time.Through regulating lamellar LPSO and agedβ′phase,the alloy achieves high strength and high damping capacity:ultimate tensile strength of 498 MPa,yield strength of 371 MPa and damping capacity of 0.02 at strain amplitude of 1×10^(−3).展开更多
The LPSO phase can effectively enhance the mechanical properties of Mg alloys.To investigate the impact of different LPSO phase contents and morphologies on the mechanical properties and strengthening mechanisms of Mg...The LPSO phase can effectively enhance the mechanical properties of Mg alloys.To investigate the impact of different LPSO phase contents and morphologies on the mechanical properties and strengthening mechanisms of Mg-Y-Al alloys under room temperature deformation,this study prepared Mg-12Y-1Al(WA121)alloys containing Bulk-LPSO(B-LPSO),Lattice-LPSO(L-LPSO),and Needle-like LPSO(N-LPSO)with different contents through different heat-treatment processes.The results indicate that with the increase in heat treatment time,the contents of B-LPSO phases remain essentially unchanged,and the contents of L-LPSO and N-LPSO phases gradually increase.The increase in N-LPSO phase content is the most pronounced,with the highest content(7.29%)observed in the alloy treated for 4.5 h.Moreover,the alloy treated for 4.5 h exhibits the best mechanical properties,with ultimate tensile strength(UTS),tensile yield strength(TYS),and elongation(EL)values of 177 MPa,139 MPa,and 4.27%,respectively.Compared to the as-cast alloy,UTS,TYS,and EL increased by 9.94%,11.2%,and 27.1%,respectively.The study reveals that all three LPSO phases exhibit excellent dislocation hindering effects,effectively enhancing strength of the alloy.Additionally,the N-LPSO phase,due to its dense distribution,forms numerous dislocation channels within the grains,dispersing stress concentration within the grains to improve plasticity of the alloy.Furthermore,the interaction between the N-LPSO phase and the other phases in the alloy can also enhance plasticity of the alloy.Therefore,the alloy treated for 4.5 h demonstrates a synergistic improvement in strength and plasticity.Research has revealed that the precipitation mechanism of the N-LPSO phase in the as-cast WA121 alloy involves the formation of an Al-rich region adjacent to the needle-like Mg_(24)Y_(5) phase.Subsequently,the Y element provided by the dissolving Mg_(24)Y_(5) phase reacts with this region,ultimately leading to the formation of the needle-like LPSO phase.展开更多
In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4...In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4)alloy cast in a steel mold was carried out.The addition of Ca element plays an important role in the refinement of LPSO structure.The result reveals new poly-types including 20H F2F2F4,60R(F2F3F3)_(3),and 66H F2F3F3F2(F6)_(4)featuring a 6-Mg structure,alongside the prevalent 18R and 14H LPSO structures.The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays,leading to the formation of a segment of 60R_(1).Moreover,the superstructure 116L,designated as(F2)_(18)F4,is formed through the ordered distribution of F4 stacking faults in 18R.展开更多
The blocky LPSO particles were modulated by single-directional and multi-directional forging,and the effect of blocky LPSO particles on the anisotropy of mechanical properties of Mg-8.5Gd-2.5Y-1.5Zn-0.5Zr alloy forged...The blocky LPSO particles were modulated by single-directional and multi-directional forging,and the effect of blocky LPSO particles on the anisotropy of mechanical properties of Mg-8.5Gd-2.5Y-1.5Zn-0.5Zr alloy forged parts was investigated.In the present work,3D processing maps are established,and the forming domain that is both stable and power efficient is in the temperature range from 430 to 500℃ and strain rate range from 0.001 to 0.06 s^(-1),which is used to guide the single-directional forging(SDF)and multi-directional forging(MDF)experiments.The tensile mechanical properties reveal that the blocky LPSO particles have an influence on the mechanical anisotropy,especially in terms of the elongation anisotropy.The blocky LPSO particles after the MDF process have a more regular shape and smaller size and are homogeneously distributed,which is responsible for the low anisotropy of the elongation.In addition,the age-hardening capability of the MDF part is higher than that of the SDF part.展开更多
Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparab...Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances.During fatigue,the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations.However,SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers.Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations.Dislocations are restricted locally and cannot glide long distances to specimen surfaces,which mitigates fatigue-induced extrusions and slip markings,ultimately leading to an increase in fatigue strength.These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.展开更多
镁合金具有比强度高、比刚度高、质量轻、切削性能好等优点,在航空航天、汽车制造及医疗服务等领域有着广泛的应用前景,但其绝对强度低,塑性差,限制了镁合金在一些领域的应用。为了改善镁合金综合性能,研究发现在镁合金中按一定比例加...镁合金具有比强度高、比刚度高、质量轻、切削性能好等优点,在航空航天、汽车制造及医疗服务等领域有着广泛的应用前景,但其绝对强度低,塑性差,限制了镁合金在一些领域的应用。为了改善镁合金综合性能,研究发现在镁合金中按一定比例加入稀土元素与过渡族元素后,会出现一种长周期有序堆垛结构(Long Period Stacking Ordered,简称LPSO相),LPSO相具有高硬度、高抗蠕变性能、高弹性模量等优点,能够同时改善合金的强度和塑性,因此,LPSO相引起了广大研究人员的关注。本文综述了稀土镁合金中LPSO相的研究进展,全面分析了LPSO相的类型及原子排布,讨论了LPSO相的形成机制和规律,以及LPSO相对合金性能的影响机制,评述了通过第一性原理对LPSO相晶体结构、弹性模量和LPSO相与层错能间关系的研究,最后对含LPSO相稀土镁合金的未来发展做出展望。展开更多
As-extruded Mg-Er-Ni alloys with different volume fractions of long-period stacking ordered(LPSO)phase and density of lamellar γ' phase were prepared,and the microstructure,mechanical,and degradation properties w...As-extruded Mg-Er-Ni alloys with different volume fractions of long-period stacking ordered(LPSO)phase and density of lamellar γ' phase were prepared,and the microstructure,mechanical,and degradation properties were investigated.Coupling the bulk LPSO phase and the lamellar γ' phase,and controlling the dynamic recrystallization processes during deformation by adjusting the volume fraction of LPSO and the density of the γ' phase,a synergistic increase in strength and degradation rate can be achieved.On the one hand,the increase in corrosion rate was related to the increased volume fraction of the bulk LPSO phase and the densities of the lamellar γ' phase,which provide more galvanic corrosion.Moreover,high densities of the lamellar γ' phase can provide more corrosion interface by inhibiting the recrystallization process to refine dynamic recrystallized(DRXed)grains during the hot extrusion.On the other hand,the ultimate tensile strength(UTS)and tensile yield strength(TYS)of the Mg-Er-Ni alloy increased from 345 and 265 MPa to 514 MPa and 358 MPa,respectively,which was mainly attributed to grain boundary and texture strengthening,bulk LPSO phase and lamellar γ' phase strengthening.Overall,Mg^(-1)4Er-4Ni alloy,which contains the highest volume fraction bulk LPSO phase and the densities of lamellar γ' phase,re-alized a synergistic enhancement of strength and degradation rate.The UTS,TYS,and degradation rate of Mg^(-1)4Er-4Ni were 514 MPa,358 MPa,and 142.5 mg cm^(-2)h^(-1)(3 wt%KCl solution at 93◦C),respectively.This research provides new insight into developing Mg alloys with high strength and degradation rates for fracturing tool materials in the application of oil and gas exploitation in harsh environments.展开更多
Effects of different volume fraction of long-period stacking ordered(LPSO)phase on the microstructure,mechanical property and anisotropy of the as-extruded Mg-xZn-yY-0.1Mn(x=1 wt%,2 wt%,4 wt%and y=2 wt%,4 wt%,8 wt%)al...Effects of different volume fraction of long-period stacking ordered(LPSO)phase on the microstructure,mechanical property and anisotropy of the as-extruded Mg-xZn-yY-0.1Mn(x=1 wt%,2 wt%,4 wt%and y=2 wt%,4 wt%,8 wt%)alloys were studied by an optical microscope,a scanning electron microscope,texture analysis,a transmission electron microscope and tensile testing.The results reveal that the volume fraction of LPSO phase increases from ZW12 to ZW24 to ZW48 alloys with the elevating Zn and Y content but constant Y/Zn value,and the mechanical strength of the LPSO-containing Mg-Zn-Y-Mn system is gradually improved when increasing LPSO phases.With the highest volume fraction of LPSO phase,ZW48 alloy presents the highest ultimate tensile strength(UTS)of 427 MPa along the extrusion direction(ED)when compared with those of ZW12 alloy with the UTS of 307 MPa and ZW24 alloy with the UTS of 347 MPa.Moreover,the elongation ratio of ZW48 alloy is maintained to moderate 9.9%,which is also the highest among three studied alloys.On the other hand,texture analysis demonstrates that the basal texture of the a-Mg phase in the ZW48 alloy is significantly weakened by the generation of more LPSO phases.On the contrary,a high texture intensity of a-Mg phase and obvious mechanical anisotropy can be observed for the ZW12 alloy.However,mechanical anisotropy still exists in the ZW48 alloy containing massive LPSO phases,which is attributed primarily to the zonal distribution of large LPSO along the ED.展开更多
基金supported by the Key Research and Development Program of Heilongjiang (2022ZX01A01)National Natural Science Foundation of China (51975167)Natural Science Foundation of Heilongjiang Province(LH2022E080)。
文摘Rare-earth(RE) magnesium alloys have attracted lots of attention due to their excellent mechanical properties.In this work,the microstructure and mechanical properties of as-extruded 8.5Gd-4.5Y-0.8Zn-0.4Zr magnesium alloy under different solution treatment were examined with the optical microscope(OM),scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM),electron back-scattered diffraction(EBSD) and Instron testing machine.The results show that the ES12alloy(solution treatment for 12 h at 520℃) has the highest ultimate tensile strength(UTS) of 390 MPa with a fracture elongation of 24.5% at the co st of a minor drop in yielding strength(YS) compared to the asextruded alloy.During solution treatment,the block-shaped long period stacking ordered(LPSO) in asextruded alloy evolves into plate-shaped LPSO,which disperses at grain boundaries(GBs),and lamellar LPSO,which distributes in grains.The coexistence of plate-shaped and lamellar LPSO,which impedes the dislocations movement,and the activated dislocations are regarded as the primary reasons for mechanical properties improvement.Furthermore,the(11-21) <1-100> texture in as-extruded alloy transforms into the(11-20) <0001> texture in ES12 alloy.The average grain size increases from 3.45 μm in as-extruded alloy to 18.70 μm in ES12 alloy.The Schmid factors of {0001} <11-20>,{10-10} <11-20>,{10-11} <11-20>,and {11-22} <11-23> increase,which indicate that slip systems are more easily activated in plastic deformation.The dynamic recrystallization(DRX) grains fraction increase to 92.8% for ES12 alloy due to the particle-stimulated nucleation(PSN) mechanism triggered by block-shaped and plate-shaped LPSO.The freshly DRXed grains further weaken the texture,and reduce the dislocation density.All of these factors increase elongation of RE magnesium alloy.
基金the financial supports from the Key Research and Development Program of Hunan Province,China(No.2023GK2020)。
文摘The homogenized Mg−5.6Gd−0.8Zn(wt.%)alloys were treated with water cooling and furnace cooling to obtain specimens without and with the 14H long-period stacking ordered(LPSO)phase.Subsequently,multi-directional forging(MDF)experiments were carried out.The microstructure and mechanical properties of different regions(the center,middle and edge regions)in the MDFed alloys were systematically investigated,and the effect of LPSO phase on them was discussed.The results show that the alloys in different regions undergo significant grain refinement during the MDF process.Inhomogeneous microstructures with different degrees of dynamic recrystallization(DRX)are formed,resulting in microhardness heterogeneity.The alloy with the LPSO phase has higher microstructure homogeneity,a higher degree of recrystallization,and better comprehensive mechanical properties than the alloy without the LPSO phase.The furnace-cooled alloy after 18 passes of MDF has the best comprehensive mechanical properties,with an ultimate compressive strength of 488 MPa,yield strength of 258 MPa,and fracture strain of 21.2%.DRX behavior is closely related to the LPSO phase and deformation temperature.The kinked LPSO phase can act as a potential nucleation site for DRX grains,while the fragmented LPSO phase promotes DRX nucleation through the particle-stimulated nucleation mechanism.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3701100)the National Natural Science Foundation of China(Nos.U20A20234,51874062)+1 种基金the Postdoctoral Science Foundation of China(Nos.2023M730390,2022M710563)the Natural Science Foundation Commission,China(Nos.CSTB2023NSCQ-BHX0164,CSTB2022NSCQ-BHX0029)。
文摘Suitable heat treatment processes were adopted to regulate the precipitation of the lamellar LPSO phase andβ′phase in Mg−Gd−Y−Zn−Zr−Nd alloy.The effects of lamellar LPSO phase andβ′phase on the mechanical properties and damping capacity of the alloy were studied systematically.Experimental results demonstrate that the lamellar LPSO phase is more conducive to dynamic recrystallization processes,leading to a high degree of recrystallization and a weak texture intensity,resulting in a higher plasticity and damping capacity.After aging treatment,theβ′precipitates exhibit pronounced aging strengthening and increase the number of mobile interfaces,thus enhancing the strength and damping capacity at the same time.Through regulating lamellar LPSO and agedβ′phase,the alloy achieves high strength and high damping capacity:ultimate tensile strength of 498 MPa,yield strength of 371 MPa and damping capacity of 0.02 at strain amplitude of 1×10^(−3).
基金supported by the Qinghai Provincial Science and Technology Department Basic Research Program(No.2025ZY029).
文摘The LPSO phase can effectively enhance the mechanical properties of Mg alloys.To investigate the impact of different LPSO phase contents and morphologies on the mechanical properties and strengthening mechanisms of Mg-Y-Al alloys under room temperature deformation,this study prepared Mg-12Y-1Al(WA121)alloys containing Bulk-LPSO(B-LPSO),Lattice-LPSO(L-LPSO),and Needle-like LPSO(N-LPSO)with different contents through different heat-treatment processes.The results indicate that with the increase in heat treatment time,the contents of B-LPSO phases remain essentially unchanged,and the contents of L-LPSO and N-LPSO phases gradually increase.The increase in N-LPSO phase content is the most pronounced,with the highest content(7.29%)observed in the alloy treated for 4.5 h.Moreover,the alloy treated for 4.5 h exhibits the best mechanical properties,with ultimate tensile strength(UTS),tensile yield strength(TYS),and elongation(EL)values of 177 MPa,139 MPa,and 4.27%,respectively.Compared to the as-cast alloy,UTS,TYS,and EL increased by 9.94%,11.2%,and 27.1%,respectively.The study reveals that all three LPSO phases exhibit excellent dislocation hindering effects,effectively enhancing strength of the alloy.Additionally,the N-LPSO phase,due to its dense distribution,forms numerous dislocation channels within the grains,dispersing stress concentration within the grains to improve plasticity of the alloy.Furthermore,the interaction between the N-LPSO phase and the other phases in the alloy can also enhance plasticity of the alloy.Therefore,the alloy treated for 4.5 h demonstrates a synergistic improvement in strength and plasticity.Research has revealed that the precipitation mechanism of the N-LPSO phase in the as-cast WA121 alloy involves the formation of an Al-rich region adjacent to the needle-like Mg_(24)Y_(5) phase.Subsequently,the Y element provided by the dissolving Mg_(24)Y_(5) phase reacts with this region,ultimately leading to the formation of the needle-like LPSO phase.
基金supported by the open research fund of Songshan Lake Materials Laboratory(No.2022SLABFN08)Guangxi Science and Technology Base and Talents Special Project(Nos.Guike AD20297034 and AD21220053)+2 种基金the National Natural Science Foundation of China(No.51801214 and 52171021)the Research Start-up Funding from Guangxi University of Science and Technology(No.03200150)the Middle-aged and Young Teachers’Basic Ability Promotion Project of Guangxi(No.2022KY0329)。
文摘In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4)alloy cast in a steel mold was carried out.The addition of Ca element plays an important role in the refinement of LPSO structure.The result reveals new poly-types including 20H F2F2F4,60R(F2F3F3)_(3),and 66H F2F3F3F2(F6)_(4)featuring a 6-Mg structure,alongside the prevalent 18R and 14H LPSO structures.The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays,leading to the formation of a segment of 60R_(1).Moreover,the superstructure 116L,designated as(F2)_(18)F4,is formed through the ordered distribution of F4 stacking faults in 18R.
基金supports of the National Key Research and Development Program of China(Grant No.2021YFB3501005)the National Natural Science Foundation of China(Grant No.52071208)the Key R&D program of Shanxi Province(International Cooperation)(Grant No.201903D421036).
文摘The blocky LPSO particles were modulated by single-directional and multi-directional forging,and the effect of blocky LPSO particles on the anisotropy of mechanical properties of Mg-8.5Gd-2.5Y-1.5Zn-0.5Zr alloy forged parts was investigated.In the present work,3D processing maps are established,and the forming domain that is both stable and power efficient is in the temperature range from 430 to 500℃ and strain rate range from 0.001 to 0.06 s^(-1),which is used to guide the single-directional forging(SDF)and multi-directional forging(MDF)experiments.The tensile mechanical properties reveal that the blocky LPSO particles have an influence on the mechanical anisotropy,especially in terms of the elongation anisotropy.The blocky LPSO particles after the MDF process have a more regular shape and smaller size and are homogeneously distributed,which is responsible for the low anisotropy of the elongation.In addition,the age-hardening capability of the MDF part is higher than that of the SDF part.
基金supported by National Natural Science Foundation of China(Nos.12102280,12172238,12332012)Postdoctoral Fellowship Program of CPSF(No.GZB20230473)+1 种基金Support of Ultramicroscopy Research Center(URC,Kyushu University)are highly acknowledged.Yao Chen acknowledges the support of JSPS Fellowship(No.JP22F22720)JSPS KAKENHI(No JP22K03828).
文摘Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances.During fatigue,the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations.However,SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers.Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations.Dislocations are restricted locally and cannot glide long distances to specimen surfaces,which mitigates fatigue-induced extrusions and slip markings,ultimately leading to an increase in fatigue strength.These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.
文摘镁合金具有比强度高、比刚度高、质量轻、切削性能好等优点,在航空航天、汽车制造及医疗服务等领域有着广泛的应用前景,但其绝对强度低,塑性差,限制了镁合金在一些领域的应用。为了改善镁合金综合性能,研究发现在镁合金中按一定比例加入稀土元素与过渡族元素后,会出现一种长周期有序堆垛结构(Long Period Stacking Ordered,简称LPSO相),LPSO相具有高硬度、高抗蠕变性能、高弹性模量等优点,能够同时改善合金的强度和塑性,因此,LPSO相引起了广大研究人员的关注。本文综述了稀土镁合金中LPSO相的研究进展,全面分析了LPSO相的类型及原子排布,讨论了LPSO相的形成机制和规律,以及LPSO相对合金性能的影响机制,评述了通过第一性原理对LPSO相晶体结构、弹性模量和LPSO相与层错能间关系的研究,最后对含LPSO相稀土镁合金的未来发展做出展望。
基金support from the National Key Research and Development Program of China(No.2021YFB3701100)the Natural Science Foundation Commission of China(Grant Nos.U20A20234 and 51874062)+1 种基金the Fundamental Re-search Funds for Central Universities(No.2022CDJKYJH004C)the Science and Technology Major Project of Shanxi Province(No.20191102008).
文摘As-extruded Mg-Er-Ni alloys with different volume fractions of long-period stacking ordered(LPSO)phase and density of lamellar γ' phase were prepared,and the microstructure,mechanical,and degradation properties were investigated.Coupling the bulk LPSO phase and the lamellar γ' phase,and controlling the dynamic recrystallization processes during deformation by adjusting the volume fraction of LPSO and the density of the γ' phase,a synergistic increase in strength and degradation rate can be achieved.On the one hand,the increase in corrosion rate was related to the increased volume fraction of the bulk LPSO phase and the densities of the lamellar γ' phase,which provide more galvanic corrosion.Moreover,high densities of the lamellar γ' phase can provide more corrosion interface by inhibiting the recrystallization process to refine dynamic recrystallized(DRXed)grains during the hot extrusion.On the other hand,the ultimate tensile strength(UTS)and tensile yield strength(TYS)of the Mg-Er-Ni alloy increased from 345 and 265 MPa to 514 MPa and 358 MPa,respectively,which was mainly attributed to grain boundary and texture strengthening,bulk LPSO phase and lamellar γ' phase strengthening.Overall,Mg^(-1)4Er-4Ni alloy,which contains the highest volume fraction bulk LPSO phase and the densities of lamellar γ' phase,re-alized a synergistic enhancement of strength and degradation rate.The UTS,TYS,and degradation rate of Mg^(-1)4Er-4Ni were 514 MPa,358 MPa,and 142.5 mg cm^(-2)h^(-1)(3 wt%KCl solution at 93◦C),respectively.This research provides new insight into developing Mg alloys with high strength and degradation rates for fracturing tool materials in the application of oil and gas exploitation in harsh environments.
基金Project supported by Guangdong Basic and Applied Basic Research Foundation(2024A1515030065,2023A1515012299)Guangzhou Science and Technology Planning Project(2024A04J6299,202201011454)+2 种基金Young Talent Support Project of Guangzhou Association for Science and Technology(QT2024-012)the National Natural Science Foundation of China(52101283)National College Students Innovation and Entrepreneurship Training Program(xj2023118450625)。
文摘Effects of different volume fraction of long-period stacking ordered(LPSO)phase on the microstructure,mechanical property and anisotropy of the as-extruded Mg-xZn-yY-0.1Mn(x=1 wt%,2 wt%,4 wt%and y=2 wt%,4 wt%,8 wt%)alloys were studied by an optical microscope,a scanning electron microscope,texture analysis,a transmission electron microscope and tensile testing.The results reveal that the volume fraction of LPSO phase increases from ZW12 to ZW24 to ZW48 alloys with the elevating Zn and Y content but constant Y/Zn value,and the mechanical strength of the LPSO-containing Mg-Zn-Y-Mn system is gradually improved when increasing LPSO phases.With the highest volume fraction of LPSO phase,ZW48 alloy presents the highest ultimate tensile strength(UTS)of 427 MPa along the extrusion direction(ED)when compared with those of ZW12 alloy with the UTS of 307 MPa and ZW24 alloy with the UTS of 347 MPa.Moreover,the elongation ratio of ZW48 alloy is maintained to moderate 9.9%,which is also the highest among three studied alloys.On the other hand,texture analysis demonstrates that the basal texture of the a-Mg phase in the ZW48 alloy is significantly weakened by the generation of more LPSO phases.On the contrary,a high texture intensity of a-Mg phase and obvious mechanical anisotropy can be observed for the ZW12 alloy.However,mechanical anisotropy still exists in the ZW48 alloy containing massive LPSO phases,which is attributed primarily to the zonal distribution of large LPSO along the ED.
