Magnesium(Mg)has great potential for application in the automotive and aerospace sectors due to its abundant resources and low density.However,the industrial applications of Mg alloys are far below alu-minum alloys.At...Magnesium(Mg)has great potential for application in the automotive and aerospace sectors due to its abundant resources and low density.However,the industrial applications of Mg alloys are far below alu-minum alloys.At present,most commercial Mg alloys exhibit a low yield strength of<300 MPa,and their specific strength does not exhibit an advantage over that of aluminum alloys and high-strength steels.Improving the strength of Mg alloys is one of the key topics in this field.In the past two decades,high-strength Mg alloys made by powder metallurgy and severe plastic deformation techniques have been reported,but the small sample dimension and high-cost limit their industrial production.Extru-sion can be used to fabricate bulk materials with fine-grained microstructures and improved mechanical properties,which is considered as a suitable route of producing high-strength Mg alloys at the indus-trial level.In this review,recent advances in the extrusion of different Mg alloys are briefly summa-rized,including commercial Mg alloys,high-alloyed Mg-RE alloys,and Ca-containing Mg alloys.Different strengthening strategies,including alloying,grain refinement,texture modification,etc.,are employed in developing high-strength Mg alloys,with special attention to a novel strengthening mechanism,namely hetero-deformation-induced strengthening,which has recently been applied to simultaneously improve the strength and ductility of Mg alloys.Therefore,the heterostructured Mg alloys prepared by extrusion are also introduced in this work,and the influences of alloying elements and extrusion parameters on the preparation of heterostructured Mg alloys are discussed systematically.Furthermore,this review summa-rizes the effect of post-extrusion treatment on the mechanical properties of extruded Mg alloys,along with a brief comparison of the mechanical properties between Mg and Al alloys.Finally,some poten-tial research directions for further advancing the high-performance and low-cost extruded Mg alloys are suggested.展开更多
Strain-controlled cyclic deformation behavior of a high-strength low-alloy(HSLA)Mg-1.2Zn-0.1Ca alloy fabricated via low-temperature extrusion at 150℃ was investigated at different strain amplitudes.Due to the partial...Strain-controlled cyclic deformation behavior of a high-strength low-alloy(HSLA)Mg-1.2Zn-0.1Ca alloy fabricated via low-temperature extrusion at 150℃ was investigated at different strain amplitudes.Due to the partial dynamic recrystallization(DRX)during extrusion,the extruded HSLA magnesium alloy consisted of a unique heterostructure containing coarse unDRX grains and ultra-fine DRX grains of0.8μm,leading to a high tensile yield strength of 374 MPa and an elongation of 14%.The HSLA magnesium alloy exhibited cyclic stabilization at strain amplitudes of≤0.4%,while cyclic hardening occurred at strain amplitudes of≥0.6%.In contrast,the homogenized alloy with a uniform coarse-grained microstructure showed a strong cyclic hardening characteristic.Compared with the homogenized alloy,the HSLA magnesium alloy had a significantly higher cyclic stress level at all strain amplitudes,along with a longer fatigue life at lower and intermediate strain amplitudes owing to its higher monotonic strength.However,the homogenized alloy showed a longer fatigue life at a high strain amplitude of 0.8%due to its better ductility and stronger capacity of storing deformation.While{10-12}<10-11>extension twinning occurred in both the homogenized and HSLA samples at high strain amplitudes,twins were primarily formed in the coarse un DRX grains in the compressive phase during cyclic deformation due to the c-axes of un DRX grains perpendicular to the loading direction,with twinning in the ultra-fine DRX grains being suppressed.The low-cycle fatigue life of both the homogenized and HSLA samples can be well predicted through an accumulative damage model based on the strain-energy density calculation and intrinsic fatigue toughness concept.展开更多
A low-alloyed Mg-1.2Zn-0.1Ca(wt.%)alloy was fabricated via low-temperature extrusion and annealing at 250℃for different times(10,30,and 90 min)to attain heterostructures with different fine-grained fractions,focusing...A low-alloyed Mg-1.2Zn-0.1Ca(wt.%)alloy was fabricated via low-temperature extrusion and annealing at 250℃for different times(10,30,and 90 min)to attain heterostructures with different fine-grained fractions,focusing on the effect of heterostructure on the mechanical properties.Partial dynamic recrystallization(RX)occurred during extrusion at 150℃,and a lamellar structure consisting of fine RX grains and coarse unRX grains was obtained.The subsequent annealing promoted static RX in the as-extruded alloy,leading to an increased fine-grained fraction from 67%to 95%.Meanwhile,the co-segregation of Zn and Ca atoms impeded the migration of grain boundaries,thus achieving a fine grain size of 0.8–1.6μm.The sample annealed for 10 min with a fine-grained fraction of 73%and an average RX grain size of 0.9μm exhibited a superior combination of high yield strength(305 MPa)and good ductility(20%).In comparison,an excellent elongation of 30%was achieved in the alloy with a nearly fully-RXed microstructure and an average grain size of 1.6μm after 90 min annealing,despite a lower yield strength of 228 MPa.In unRX grains,the hard orientation with(01–10)parallel to the extrusion direction and high-density dislocations made it more difficult to deform compared with the RX grains,thus producing hetero-deformation induced(HDI)strengthening.Besides fine grains and high-density dislocations,HDI strengthening is the key to achieving the superior mechanical properties of the low-alloyed Mg alloy.展开更多
基金sponsored by the Key-Area Research and De-velopment Program of Guangdong Province(No.2020B010186002)the Natural Science Foundation of Guangdong for Research Team(No.2015A030312003)+2 种基金the Yangcheng Scholars Research Project of Guangzhou Education Bureau(No.202032806)Daolun Chen is grateful for the financial support from the Natural Sci-ences and Engineering Research Council of Canada(NSERC)Hua Wang thanks the Study Abroad Fund for supporting his study at Toronto Metropolitan University。
文摘Magnesium(Mg)has great potential for application in the automotive and aerospace sectors due to its abundant resources and low density.However,the industrial applications of Mg alloys are far below alu-minum alloys.At present,most commercial Mg alloys exhibit a low yield strength of<300 MPa,and their specific strength does not exhibit an advantage over that of aluminum alloys and high-strength steels.Improving the strength of Mg alloys is one of the key topics in this field.In the past two decades,high-strength Mg alloys made by powder metallurgy and severe plastic deformation techniques have been reported,but the small sample dimension and high-cost limit their industrial production.Extru-sion can be used to fabricate bulk materials with fine-grained microstructures and improved mechanical properties,which is considered as a suitable route of producing high-strength Mg alloys at the indus-trial level.In this review,recent advances in the extrusion of different Mg alloys are briefly summa-rized,including commercial Mg alloys,high-alloyed Mg-RE alloys,and Ca-containing Mg alloys.Different strengthening strategies,including alloying,grain refinement,texture modification,etc.,are employed in developing high-strength Mg alloys,with special attention to a novel strengthening mechanism,namely hetero-deformation-induced strengthening,which has recently been applied to simultaneously improve the strength and ductility of Mg alloys.Therefore,the heterostructured Mg alloys prepared by extrusion are also introduced in this work,and the influences of alloying elements and extrusion parameters on the preparation of heterostructured Mg alloys are discussed systematically.Furthermore,this review summa-rizes the effect of post-extrusion treatment on the mechanical properties of extruded Mg alloys,along with a brief comparison of the mechanical properties between Mg and Al alloys.Finally,some poten-tial research directions for further advancing the high-performance and low-cost extruded Mg alloys are suggested.
基金Key-Area Research and Development Program of Guangdong Province(No.2020B010186002)Natural Science Foundation of Guangdong for Research Team(No.2015A030312003)+1 种基金financial support by Natural Sciences and Engineering Research Council of Canada(NSERC)Study Abroad Fund for supporting his study at Toronto Metropolitan University。
文摘Strain-controlled cyclic deformation behavior of a high-strength low-alloy(HSLA)Mg-1.2Zn-0.1Ca alloy fabricated via low-temperature extrusion at 150℃ was investigated at different strain amplitudes.Due to the partial dynamic recrystallization(DRX)during extrusion,the extruded HSLA magnesium alloy consisted of a unique heterostructure containing coarse unDRX grains and ultra-fine DRX grains of0.8μm,leading to a high tensile yield strength of 374 MPa and an elongation of 14%.The HSLA magnesium alloy exhibited cyclic stabilization at strain amplitudes of≤0.4%,while cyclic hardening occurred at strain amplitudes of≥0.6%.In contrast,the homogenized alloy with a uniform coarse-grained microstructure showed a strong cyclic hardening characteristic.Compared with the homogenized alloy,the HSLA magnesium alloy had a significantly higher cyclic stress level at all strain amplitudes,along with a longer fatigue life at lower and intermediate strain amplitudes owing to its higher monotonic strength.However,the homogenized alloy showed a longer fatigue life at a high strain amplitude of 0.8%due to its better ductility and stronger capacity of storing deformation.While{10-12}<10-11>extension twinning occurred in both the homogenized and HSLA samples at high strain amplitudes,twins were primarily formed in the coarse un DRX grains in the compressive phase during cyclic deformation due to the c-axes of un DRX grains perpendicular to the loading direction,with twinning in the ultra-fine DRX grains being suppressed.The low-cycle fatigue life of both the homogenized and HSLA samples can be well predicted through an accumulative damage model based on the strain-energy density calculation and intrinsic fatigue toughness concept.
基金the Key-Area Research and Development Program of Guangdong Province(No.2020B010186002)the Natural Science Foundation of Guangdong for Research Team(No.2015A030312003)。
文摘A low-alloyed Mg-1.2Zn-0.1Ca(wt.%)alloy was fabricated via low-temperature extrusion and annealing at 250℃for different times(10,30,and 90 min)to attain heterostructures with different fine-grained fractions,focusing on the effect of heterostructure on the mechanical properties.Partial dynamic recrystallization(RX)occurred during extrusion at 150℃,and a lamellar structure consisting of fine RX grains and coarse unRX grains was obtained.The subsequent annealing promoted static RX in the as-extruded alloy,leading to an increased fine-grained fraction from 67%to 95%.Meanwhile,the co-segregation of Zn and Ca atoms impeded the migration of grain boundaries,thus achieving a fine grain size of 0.8–1.6μm.The sample annealed for 10 min with a fine-grained fraction of 73%and an average RX grain size of 0.9μm exhibited a superior combination of high yield strength(305 MPa)and good ductility(20%).In comparison,an excellent elongation of 30%was achieved in the alloy with a nearly fully-RXed microstructure and an average grain size of 1.6μm after 90 min annealing,despite a lower yield strength of 228 MPa.In unRX grains,the hard orientation with(01–10)parallel to the extrusion direction and high-density dislocations made it more difficult to deform compared with the RX grains,thus producing hetero-deformation induced(HDI)strengthening.Besides fine grains and high-density dislocations,HDI strengthening is the key to achieving the superior mechanical properties of the low-alloyed Mg alloy.
