The corrosion behavior of the tungsten inert gas(TIG)welded Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy with different post-weld heat treatments was systematically investigated.The results show that the corrosion resistance of the s...The corrosion behavior of the tungsten inert gas(TIG)welded Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy with different post-weld heat treatments was systematically investigated.The results show that the corrosion resistance of the sand-cast base material(BM)was inferior to that of the fusion zone(FZ),which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg_3(Nd,Gd)eutectic phases and numerousβprecipitates.It is found that post-weld solid-solution(T4)treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution.The precipitation of nanosized phases and Zn-Zr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged(T6) joint.As the main corrosion products,MgO and Mg(OH)_(2) are distributed throughout the whole corrosion film,while RE oxides and RE hydroxides are mainly distributed in the inner layer,which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)_(2).Based on the composition and structure of the corrosion product film,a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints.This work could promote the applications of welded Mg-RE alloy joint in some corrosion environments.展开更多
The effect of plastic deformation prior to artificial aging on the aging characteristics and mechanical properties of a Mg-11Gd-2Nd-0.5Zr (mass fraction, %) alloy was investigated. After solution treatment at 525 ℃ f...The effect of plastic deformation prior to artificial aging on the aging characteristics and mechanical properties of a Mg-11Gd-2Nd-0.5Zr (mass fraction, %) alloy was investigated. After solution treatment at 525 ℃ for 4 h, the alloy was subjected to cold stretching deformation of 0%, 5% and 10%, respectively. The as-deformed specimens possess high density of dislocations and mechanical twins, which increase with elevated deformation. As compared with non-stretched alloy, the stretched alloy shows accelerated age-hardening response and slightly enhanced peak hardness when aged at 200 ℃. Comparison of the microstructures in undeformed and deformed specimens after 200 ℃, 24 h aging reveals that pre-deformation induces the heterogeneous nucleation of precipitations at dislocations and twin boundaries in addition to the homogeneous precipitation in the matrix. Room and high temperature tensile test results show that pre-deformation enhances the strength of the alloy, especially at room temperature, though the ductility declines. The improvement in strength of deformed and aged alloy is attributed to the combined strengthening effect of precipitates, deformation structures and grain boundaries.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
基金supported by the National Natural Science Foundation of China(Nos.U2037601,U2241231,and 51821001)。
文摘The corrosion behavior of the tungsten inert gas(TIG)welded Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy with different post-weld heat treatments was systematically investigated.The results show that the corrosion resistance of the sand-cast base material(BM)was inferior to that of the fusion zone(FZ),which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg_3(Nd,Gd)eutectic phases and numerousβprecipitates.It is found that post-weld solid-solution(T4)treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution.The precipitation of nanosized phases and Zn-Zr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged(T6) joint.As the main corrosion products,MgO and Mg(OH)_(2) are distributed throughout the whole corrosion film,while RE oxides and RE hydroxides are mainly distributed in the inner layer,which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)_(2).Based on the composition and structure of the corrosion product film,a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints.This work could promote the applications of welded Mg-RE alloy joint in some corrosion environments.
文摘The effect of plastic deformation prior to artificial aging on the aging characteristics and mechanical properties of a Mg-11Gd-2Nd-0.5Zr (mass fraction, %) alloy was investigated. After solution treatment at 525 ℃ for 4 h, the alloy was subjected to cold stretching deformation of 0%, 5% and 10%, respectively. The as-deformed specimens possess high density of dislocations and mechanical twins, which increase with elevated deformation. As compared with non-stretched alloy, the stretched alloy shows accelerated age-hardening response and slightly enhanced peak hardness when aged at 200 ℃. Comparison of the microstructures in undeformed and deformed specimens after 200 ℃, 24 h aging reveals that pre-deformation induces the heterogeneous nucleation of precipitations at dislocations and twin boundaries in addition to the homogeneous precipitation in the matrix. Room and high temperature tensile test results show that pre-deformation enhances the strength of the alloy, especially at room temperature, though the ductility declines. The improvement in strength of deformed and aged alloy is attributed to the combined strengthening effect of precipitates, deformation structures and grain boundaries.
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).
