【目的】旨在实现压铸镁合金高质量焊接,其是拓宽镁合金在工业领域应用的关键。【方法】为改善压铸镁合金常规交流非熔化极惰性气体保护焊(Tungsten inert gas welding,TIG)接头质量,利用超声频电信号激发电弧,产生作用于电弧及熔池的超...【目的】旨在实现压铸镁合金高质量焊接,其是拓宽镁合金在工业领域应用的关键。【方法】为改善压铸镁合金常规交流非熔化极惰性气体保护焊(Tungsten inert gas welding,TIG)接头质量,利用超声频电信号激发电弧,产生作用于电弧及熔池的超声,对比研究超声电弧对AZ31B压铸镁合金平板对接接头的成形、金相组织及力学性能的影响。【结果】结果表明,超声电弧可以提高焊缝成形性能、细化焊缝组织以及提高接头的强度和塑性。与常规TIG相比,施加超声激励扩展了焊缝中下部熔宽,使得接头表面和边界熔化均匀,焊缝晶粒得到细化。同时,抑制了第二相的聚集和长大,促进其在焊缝中的均匀分布;接头的平均抗拉强度为212 MPa,达到母材的80.9%,断后伸长率由5.1%增高至8.5%;未施加超声电弧的接头拉伸试样在焊缝中断裂,引入超声电弧的接头拉伸试样在热影响区断裂,断口均呈现出准解理断裂的特征。【结论】超声电弧的引入有助于改善压铸镁合金焊接质量,显著提高接头力学性能。展开更多
镁合金在汽车、航空航天、电子工业等领域的应用日益广泛。为了准确描述AZ31B镁合金在高速冲击荷载作用下的响应,建立了金属动态本构模型,并编译成VUMAT用户子程序。采用万能试验机进行了光滑圆棒的准静态拉伸和异形剪切试验,基于ABAQUS...镁合金在汽车、航空航天、电子工业等领域的应用日益广泛。为了准确描述AZ31B镁合金在高速冲击荷载作用下的响应,建立了金属动态本构模型,并编译成VUMAT用户子程序。采用万能试验机进行了光滑圆棒的准静态拉伸和异形剪切试验,基于ABAQUS/EXPLICIT建立了有限元模型,通过数值模拟校准了AZ31B镁合金的强度模型和失效准则的相关参数。通过对比数值模拟结果与0.5-cal FSP子弹及20 mm FSP子弹冲击AZ31B镁合金靶板试验结果,验证了模型的精确性和适用性,分析了弹头形状和靶板厚度对弹丸高速侵彻AZ31B镁合金的影响。研究发现:当前模型能较好地预测靶板的弹道极限和穿孔破坏形貌;不同形状弹丸冲击下AZ31B镁合金靶板的失效机制不同,平头弹对应的弹道极限最大,锥形弹对应的弹道极限最小;靶板厚度会影响失效模式,厚靶以剪切破坏为主,而薄靶以弯曲变形和花瓣形撕裂破坏为主。展开更多
This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode ...This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode positive(DCEP)polarities yielded crack-free partial penetration welds for6 mm thick AZ31B alloy sheet.Welding under direct current electrode negative(DCEN)polarity with identical parameters as that for AC and DCEP resulted in full penetration welds that had microcracks.Defect-free full-penetration welds could be accomplished with pulse GTA welding using DCEN polarity at a pulse frequency of 1 Hz with a pulse duration ratio of 1:1.The resultant DCEN P 1:1 weld metal had a microstructure finer than the conventional DCEN weld.Welds produced with pulse duration ratios of 1:2and 1:4 lacked penetration but had a much finer microstructures because of the lower heat input.The arc constriction by the high frequency pulsing in the Activ Arc■-High frequency(AA-HF)mode welding was responsible for deeper penetration.Welds produced under DCEN pulsing and AA-HF conditions had hardness higher than conventional DCEN,DCEP and AC GTA welds,attributed to the finer microstructure.AA-HF GTA welding produced defect free deeper penetration welds with good microstructural features/mechanical properties and also gave an advantage of 50%enhanced productivity when welded at1500 Hz.展开更多
In this study,laser-assisted plasma electrolytic oxidation(Laser/PEO)coating was prepared on AZ31B magnesium alloy for corrosion protection,due to insufficient corrosion protection caused by the inherent defects,crack...In this study,laser-assisted plasma electrolytic oxidation(Laser/PEO)coating was prepared on AZ31B magnesium alloy for corrosion protection,due to insufficient corrosion protection caused by the inherent defects,cracks and poor quality of PEO coatings.The plasma discharge evolution,morphological characteristics,elemental composition during coating growth were characterized by high-speed camera,SEM,EDX,XRD and XPS,respectively.Meanwhile,Mott Schottky(M-S)curves,potentiodynamic polarization(PDP)curves and electrochemical impedance spectroscopy(EIS)tests characterized the oxygen vacancy defects and corrosion resistance of the coatings.The results demonstrated that laser-assisted irradiation not only induced plasma discharge on the anode surface,but also limited the plasma discharge size in the post-processing stage,which significantly increased the proportion of corrosion-resistant phase Mg_(2)SiO_(4)(the proportion of Mg_(2)SiO_(4)increased from 23.70%to 39.22%),thickness and density in the coating,and obviously reduced the oxygen vacancy defects and microcracks in the coating.As a result,the corrosion resistance of the Laser/PEO coating(9.29(±0.76)×10^(-7)A·cm^(-2))was further enhanced in comparation with the PEO coating(3.06(±0.19)×10^(-6) A·cm^(-2)).展开更多
In this work,AZ31B extruded sheets with mixed-grain microstructures were prepared through extrusion.Samples of mixed-grain microstructure with different morphologies were selected from the AZ31B extruded sheets(referr...In this work,AZ31B extruded sheets with mixed-grain microstructures were prepared through extrusion.Samples of mixed-grain microstructure with different morphologies were selected from the AZ31B extruded sheets(referred to as M1 and M2 samples,respectively).The creep tests were performed on these samples at the temperature range of 150-200℃,and the stress level range of 50-100 MPa.The creep properties and fracture behavior of AZ31 extruded sheets with mixed-grain microstructures were studied.Results showed that the creep properties of the M2 sample always outperformed that of the M1 sample and M1 and M2 samples’creep was dominated by dislocation movement.The creep rate of M2 samples(1.5×10^(-7)±1.1×10^(-10) s^(-1))is an order of magnitude lower than that of M1 samples(4.8×10^(-6)±8.1×10^(-10) s^(-1))at 200℃under 50 MPa The high activity of basal slip and softening mechanism in the M1 sample significantly accelerated creep,resulting in a relatively high creep rate.Moreover,the stress concentration within the M1 sample caused by deformation incompatibility,increased the initiation and propagation of voids,ultimately leading to fracture and poorer creep performance.However,the numerous<10µm fine grains surrounding deformed coarse grains in the M2 sample facilitated better coordination of deformation through dislocation slip,effectively slowing down the initiation of voids during the creep process.Meanwhile,the strain was uniformly distributed within each grain,mitigating stress concentration,inhibiting voids propagation,and contributing to the superior creep resistance of the M2 sample.展开更多
Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mec...Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.展开更多
文摘【目的】旨在实现压铸镁合金高质量焊接,其是拓宽镁合金在工业领域应用的关键。【方法】为改善压铸镁合金常规交流非熔化极惰性气体保护焊(Tungsten inert gas welding,TIG)接头质量,利用超声频电信号激发电弧,产生作用于电弧及熔池的超声,对比研究超声电弧对AZ31B压铸镁合金平板对接接头的成形、金相组织及力学性能的影响。【结果】结果表明,超声电弧可以提高焊缝成形性能、细化焊缝组织以及提高接头的强度和塑性。与常规TIG相比,施加超声激励扩展了焊缝中下部熔宽,使得接头表面和边界熔化均匀,焊缝晶粒得到细化。同时,抑制了第二相的聚集和长大,促进其在焊缝中的均匀分布;接头的平均抗拉强度为212 MPa,达到母材的80.9%,断后伸长率由5.1%增高至8.5%;未施加超声电弧的接头拉伸试样在焊缝中断裂,引入超声电弧的接头拉伸试样在热影响区断裂,断口均呈现出准解理断裂的特征。【结论】超声电弧的引入有助于改善压铸镁合金焊接质量,显著提高接头力学性能。
文摘镁合金在汽车、航空航天、电子工业等领域的应用日益广泛。为了准确描述AZ31B镁合金在高速冲击荷载作用下的响应,建立了金属动态本构模型,并编译成VUMAT用户子程序。采用万能试验机进行了光滑圆棒的准静态拉伸和异形剪切试验,基于ABAQUS/EXPLICIT建立了有限元模型,通过数值模拟校准了AZ31B镁合金的强度模型和失效准则的相关参数。通过对比数值模拟结果与0.5-cal FSP子弹及20 mm FSP子弹冲击AZ31B镁合金靶板试验结果,验证了模型的精确性和适用性,分析了弹头形状和靶板厚度对弹丸高速侵彻AZ31B镁合金的影响。研究发现:当前模型能较好地预测靶板的弹道极限和穿孔破坏形貌;不同形状弹丸冲击下AZ31B镁合金靶板的失效机制不同,平头弹对应的弹道极限最大,锥形弹对应的弹道极限最小;靶板厚度会影响失效模式,厚靶以剪切破坏为主,而薄靶以弯曲变形和花瓣形撕裂破坏为主。
文摘This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode positive(DCEP)polarities yielded crack-free partial penetration welds for6 mm thick AZ31B alloy sheet.Welding under direct current electrode negative(DCEN)polarity with identical parameters as that for AC and DCEP resulted in full penetration welds that had microcracks.Defect-free full-penetration welds could be accomplished with pulse GTA welding using DCEN polarity at a pulse frequency of 1 Hz with a pulse duration ratio of 1:1.The resultant DCEN P 1:1 weld metal had a microstructure finer than the conventional DCEN weld.Welds produced with pulse duration ratios of 1:2and 1:4 lacked penetration but had a much finer microstructures because of the lower heat input.The arc constriction by the high frequency pulsing in the Activ Arc■-High frequency(AA-HF)mode welding was responsible for deeper penetration.Welds produced under DCEN pulsing and AA-HF conditions had hardness higher than conventional DCEN,DCEP and AC GTA welds,attributed to the finer microstructure.AA-HF GTA welding produced defect free deeper penetration welds with good microstructural features/mechanical properties and also gave an advantage of 50%enhanced productivity when welded at1500 Hz.
基金The National Natural Science Foundation of China(U2130122,U22A20199,and 51975533)Natural Science Foundation of Zhejiang Province(LGJ22E050002)+1 种基金Equipment pre-research joint fund project of the Ministry of Education(8091B022215)China Postdoctoral Science Foundation(2023M733147)funded this research.
文摘In this study,laser-assisted plasma electrolytic oxidation(Laser/PEO)coating was prepared on AZ31B magnesium alloy for corrosion protection,due to insufficient corrosion protection caused by the inherent defects,cracks and poor quality of PEO coatings.The plasma discharge evolution,morphological characteristics,elemental composition during coating growth were characterized by high-speed camera,SEM,EDX,XRD and XPS,respectively.Meanwhile,Mott Schottky(M-S)curves,potentiodynamic polarization(PDP)curves and electrochemical impedance spectroscopy(EIS)tests characterized the oxygen vacancy defects and corrosion resistance of the coatings.The results demonstrated that laser-assisted irradiation not only induced plasma discharge on the anode surface,but also limited the plasma discharge size in the post-processing stage,which significantly increased the proportion of corrosion-resistant phase Mg_(2)SiO_(4)(the proportion of Mg_(2)SiO_(4)increased from 23.70%to 39.22%),thickness and density in the coating,and obviously reduced the oxygen vacancy defects and microcracks in the coating.As a result,the corrosion resistance of the Laser/PEO coating(9.29(±0.76)×10^(-7)A·cm^(-2))was further enhanced in comparation with the PEO coating(3.06(±0.19)×10^(-6) A·cm^(-2)).
基金supported by the National Natural Science Foundation of China(52474419,52374395)Natural Science Foundation of Shanxi Province(20210302123135,202303021221143)+3 种基金Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi Province(202104021301022,202204021301009)Central Government Guided Local Science and Technology development projects(YDZJSX20231B003,YDZJSX2021A010)The Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant(No.075-15-2022-1133)the National Research Foundation(NRF)grant funded by the Ministry of Science and ICT(2015R1A2A1A01006795)of Korea through the Research Institute of Advanced.
文摘In this work,AZ31B extruded sheets with mixed-grain microstructures were prepared through extrusion.Samples of mixed-grain microstructure with different morphologies were selected from the AZ31B extruded sheets(referred to as M1 and M2 samples,respectively).The creep tests were performed on these samples at the temperature range of 150-200℃,and the stress level range of 50-100 MPa.The creep properties and fracture behavior of AZ31 extruded sheets with mixed-grain microstructures were studied.Results showed that the creep properties of the M2 sample always outperformed that of the M1 sample and M1 and M2 samples’creep was dominated by dislocation movement.The creep rate of M2 samples(1.5×10^(-7)±1.1×10^(-10) s^(-1))is an order of magnitude lower than that of M1 samples(4.8×10^(-6)±8.1×10^(-10) s^(-1))at 200℃under 50 MPa The high activity of basal slip and softening mechanism in the M1 sample significantly accelerated creep,resulting in a relatively high creep rate.Moreover,the stress concentration within the M1 sample caused by deformation incompatibility,increased the initiation and propagation of voids,ultimately leading to fracture and poorer creep performance.However,the numerous<10µm fine grains surrounding deformed coarse grains in the M2 sample facilitated better coordination of deformation through dislocation slip,effectively slowing down the initiation of voids during the creep process.Meanwhile,the strain was uniformly distributed within each grain,mitigating stress concentration,inhibiting voids propagation,and contributing to the superior creep resistance of the M2 sample.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52005240,52164045)Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province(No.20212BCJ23028)Outstanding Youth Foundation in Jiangxi Province(No.20224ACB214012).
文摘Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.
