利用光学显微镜(Optical microscope,OM)、X射线衍射仪(X-ray diffractometer,XRD)、扫描电子显微镜(Scanning electron microscope,SEM)、能谱分析仪(Energy dispersive spectrometer,EDS)、透射电镜(Transmission electron microscope...利用光学显微镜(Optical microscope,OM)、X射线衍射仪(X-ray diffractometer,XRD)、扫描电子显微镜(Scanning electron microscope,SEM)、能谱分析仪(Energy dispersive spectrometer,EDS)、透射电镜(Transmission electron microscope,TEM)和电子万能试验机等手段对传统砂型重力铸造方法制备的EV31A合金的显微组织和性能进行了深入研究。实验结果表明:铸态EV31A合金的显微组织由α-Mg和α-Mg+Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)共晶相组成,由于稀土元素含量较少,共晶反应发生在α-Mg结晶后期,表现为除少量固溶于α-Mg基体中,含稀土元素的Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)相主要分布在α-Mg的晶界处。Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)相为bcc结构,晶格常数为0.285 nm,呈鱼骨状,尺寸在数十微米。合金中α-Mg基体的晶粒尺寸为56.8μm。EV31A铸态合金的抗拉强度、屈服强度和延伸率分别为207 MPa、124 MPa和7.0%。合金具有优异力学性能主要归因于Zr元素所带来的细晶强化,Gd、Nd、Zr等溶质原子的固溶强化,共晶Mg_(41)(Nd_(0.9),Gd_(0.1))_(5)相所带来的第二相强化等多种强化方式的协同作用。展开更多
To improve the ductility of a commercial Mg−rare earth alloy EV31A(Mg−3Nd−1.5Gd−0.3Zn−0.5Zr),a heat treatment method called double aging is explored,and its effect on mechanical properties and microstructure of the al...To improve the ductility of a commercial Mg−rare earth alloy EV31A(Mg−3Nd−1.5Gd−0.3Zn−0.5Zr),a heat treatment method called double aging is explored,and its effect on mechanical properties and microstructure of the alloy is studied.Ultimate strength and elongation of the alloy can be increased to 288 MPa and 6.6%by the optimum double aging process,compared to 273 MPa and 4.9%after single aging.Time consumption of the aging process is also significantly decreased from 16 h(single aging)to 2 h.HAADF-STEM characterization shows that the primary precipitate isβ'phase,which is similar toβ'phase in Mg−Nd binary alloy.By double aging,theβ'phase is finer and more densely distributed compared with single aging,with approximately double density and half size,which explains the improvement in strength and ductility.展开更多
The effect of a low-frequency alternating magnetic field (AMF,0 A 0 Hz,5 A 10 Hz,10 A 10 Hz,15 A 10 Hz) on the hot tearing susceptibility (HTS) of a magnesium alloy (EV31) was systematically studied using a combinatio...The effect of a low-frequency alternating magnetic field (AMF,0 A 0 Hz,5 A 10 Hz,10 A 10 Hz,15 A 10 Hz) on the hot tearing susceptibility (HTS) of a magnesium alloy (EV31) was systematically studied using a combination of experiment and numerical simulation.By observing the macroscopic hot cracks in hot joints of the "T" samples,the hot tearing tendency of the samples was analyzed.The HTS of the alloy can be predicted via numerical simulation and the crack susceptibility coefficient (CSC).The microstructure and morphology of the hot tearing zone of EV31 were investigated using scanning electron microscopy (SEM).Results show that increasing the magnetic field strength reduces both the alloy solidification temperature range and the dendrite coherency temperature,which increases the feeding time during solidification and decreases the HTS of the alloy.When the magnetic field parameters are 10 Hz 15 A,the EV31 alloy shows the lowest HTS.The main component of the second phase in the microstructure is Mg12Nd.This study also found that the electromagnetic field can effectively refine the grains,purify the melt,and reduce the oxide content in the melt.The obtained simulation results are consistent with the experimental results.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.51825101).
文摘To improve the ductility of a commercial Mg−rare earth alloy EV31A(Mg−3Nd−1.5Gd−0.3Zn−0.5Zr),a heat treatment method called double aging is explored,and its effect on mechanical properties and microstructure of the alloy is studied.Ultimate strength and elongation of the alloy can be increased to 288 MPa and 6.6%by the optimum double aging process,compared to 273 MPa and 4.9%after single aging.Time consumption of the aging process is also significantly decreased from 16 h(single aging)to 2 h.HAADF-STEM characterization shows that the primary precipitate isβ'phase,which is similar toβ'phase in Mg−Nd binary alloy.By double aging,theβ'phase is finer and more densely distributed compared with single aging,with approximately double density and half size,which explains the improvement in strength and ductility.
基金financially supported by the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science(2019JH3/30100014)the Innovation Talent Program in Science and Technologies for Young Middleaged Scientists of Shengyang(RC200414)。
文摘The effect of a low-frequency alternating magnetic field (AMF,0 A 0 Hz,5 A 10 Hz,10 A 10 Hz,15 A 10 Hz) on the hot tearing susceptibility (HTS) of a magnesium alloy (EV31) was systematically studied using a combination of experiment and numerical simulation.By observing the macroscopic hot cracks in hot joints of the "T" samples,the hot tearing tendency of the samples was analyzed.The HTS of the alloy can be predicted via numerical simulation and the crack susceptibility coefficient (CSC).The microstructure and morphology of the hot tearing zone of EV31 were investigated using scanning electron microscopy (SEM).Results show that increasing the magnetic field strength reduces both the alloy solidification temperature range and the dendrite coherency temperature,which increases the feeding time during solidification and decreases the HTS of the alloy.When the magnetic field parameters are 10 Hz 15 A,the EV31 alloy shows the lowest HTS.The main component of the second phase in the microstructure is Mg12Nd.This study also found that the electromagnetic field can effectively refine the grains,purify the melt,and reduce the oxide content in the melt.The obtained simulation results are consistent with the experimental results.
