为研究Mg-Gd-Er-Zn稀土变形镁合金微观组织与力学性能,通过金属模铸造、固溶处理、热挤压和时效处理工艺过程,制备了Mg-Gd-Er-Zn稀土变形镁合金,并利用金相显微镜(optical microscopy,OM)、X射线衍射仪(Xray diffraction,XRD)、扫描电镜...为研究Mg-Gd-Er-Zn稀土变形镁合金微观组织与力学性能,通过金属模铸造、固溶处理、热挤压和时效处理工艺过程,制备了Mg-Gd-Er-Zn稀土变形镁合金,并利用金相显微镜(optical microscopy,OM)、X射线衍射仪(Xray diffraction,XRD)、扫描电镜(scanning electron microscopy,SEM)及透射电镜(transmission electron microscopy,TEM)等手段进行表征.结果表明:Mg-Gd-Er-Zn合金的铸态组织主要由α-Mg基体和沿晶界分布的(Mg,Zn)3Gd第2相组成,固溶后生成层片状的长周期堆垛有序(long period stacking ordered,LPSO)结构;经过热挤压变形,合金的晶粒得到显著细化;时效处理过程中,合金中析出纳米级尺寸的β'相.最终时效态合金的室温抗拉强度、屈服强度和伸长率可分别达397.5 MPa、359.0 MPa和6.0%.展开更多
The effects of homogenization and isothermal aging treatment on the mechanical properties of Mg-12Gd- 2Er-1Zn-0.6Zr （wt%） alloy were investigated. The precipitated long-period stacking order （LPSO） structure and t...The effects of homogenization and isothermal aging treatment on the mechanical properties of Mg-12Gd- 2Er-1Zn-0.6Zr （wt%） alloy were investigated. The precipitated long-period stacking order （LPSO） structure and the aging precipitation sequence of the conditioned alloys were observed and analyzed, respectively. The results indicate that the 14H-LPSO structure occurs after the homogenization treatment and the 131 phase forms after the isothermal aging process. These two independent processes could be controlled by the precipitation temperature range. The significant increase in the elongation of the as-cast alloy after homogenization treatment is attributed to the disappearance of the coarse primary Mgs（Gd, Er, Zn） phase and the presence of the 14H-LPSO structure. The precipitation sequence of the investigated alloy is α-Mg（SSS）/β″（D019）/β′（cbco）/β. Furthermore, the yield tensile strength （YTS） and ultimate tensile strength （UTS） values of the isothermal aging alloy have a great improvement, which could be attributed to the high density of the precipitated β′ phase.展开更多
In this work,the effects of Zn content(0-2 wt%)on microstructural evolution and mechanical properties of cast Mg-10Gd-3.5Er-0.5Zr alloys are studied.The results show that the as-cast Mg-10Gd-3.5Er-xZn-0.5Zr alloys are...In this work,the effects of Zn content(0-2 wt%)on microstructural evolution and mechanical properties of cast Mg-10Gd-3.5Er-0.5Zr alloys are studied.The results show that the as-cast Mg-10Gd-3.5Er-xZn-0.5Zr alloys are mainly composed of Mg matrix and secondary(Mg,Zn)3(Gd,Er)phases distributed along grain boundaries.With the increase in Zn content,the volume fraction of secondary(Mg,Zn)3(Gd,Er)phases increases and the grains get refined.In the process of solid solution treatment,Zn addition can lead to the formation of long-period stacking ordered(LPSO)structures and the volume fraction of LPSO structures increases with Zn content.In addition,the Zn addition can reduce the vacancy formation energy and accelerate the diffusion rate of RE elements in Mg matrix.Because of the comprehensive effect of secondary phases and the accelerated diffusion rate,the base alloy and 2Zn alloy have less grain growth after solid solution treatment than that of the 0.5Zn alloy and 1 Zn alloy.The precipitation process is also accelerated by enhanced diffusion rate.At room temperature(RT),the strengthening effect of β’+β1 precipitates is more effective than that of LPSO structures,so the peak-aged 0.5Zn alloy exhibits the most excellent mechanical performance at RT,with yield strength of 219 MPa,ultimate tensile strength 296 MPa and elongation of 6.4%.While LPSO structures have stronger strengthening effect at elevated temperature than that of β’+β1 precipitates,so the 1Zn alloy and 2Zn alloy have more stable mechanical performance than that of the base alloy and 0.5Zn alloy with the increase in tensile temperature.展开更多
The microstructures of as-cast and as-solution Mg–12Gd–2Er–1Zn–0.6Zr alloys were investigated by optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, highresoluti...The microstructures of as-cast and as-solution Mg–12Gd–2Er–1Zn–0.6Zr alloys were investigated by optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, highresolution transmission electron microscopy（HRTEM）X-ray diffraction（XRD） and selected-area electron diffraction（SAED） in the present investigation. The results show that the primary eutectic phase Mg5（Gd, Er, Zn） and some flocculent features are found in the as-cast alloy; the SAED pattern indicates that these flocculent features are the dense areas of stacking faults. The 14H-LPSO structure precipitates in the temperature range of 673–793 K, and the volume fraction of 14H-LPSO structure increases with the extension of heating time; however, there is no precipitation of 14H-LPSO structure when the temperature reaches up to 803 K. In addition, the Mg5（Gd, Er, Zn） phase dissolves gradually along with the precipitation of 14H-LPSO structure.展开更多
文摘为研究Mg-Gd-Er-Zn稀土变形镁合金微观组织与力学性能,通过金属模铸造、固溶处理、热挤压和时效处理工艺过程,制备了Mg-Gd-Er-Zn稀土变形镁合金,并利用金相显微镜(optical microscopy,OM)、X射线衍射仪(Xray diffraction,XRD)、扫描电镜(scanning electron microscopy,SEM)及透射电镜(transmission electron microscopy,TEM)等手段进行表征.结果表明:Mg-Gd-Er-Zn合金的铸态组织主要由α-Mg基体和沿晶界分布的(Mg,Zn)3Gd第2相组成,固溶后生成层片状的长周期堆垛有序(long period stacking ordered,LPSO)结构;经过热挤压变形,合金的晶粒得到显著细化;时效处理过程中,合金中析出纳米级尺寸的β'相.最终时效态合金的室温抗拉强度、屈服强度和伸长率可分别达397.5 MPa、359.0 MPa和6.0%.
基金financially supported by Beijing Natural Science Foundation(No.2142005)the National Natural Science Foundation of China(No.51401005)the Ri Xin Talents Plan of Beijing University of Technology(Nos.2014-RX-L07 and2015-RX-L11)
文摘The effects of homogenization and isothermal aging treatment on the mechanical properties of Mg-12Gd- 2Er-1Zn-0.6Zr （wt%） alloy were investigated. The precipitated long-period stacking order （LPSO） structure and the aging precipitation sequence of the conditioned alloys were observed and analyzed, respectively. The results indicate that the 14H-LPSO structure occurs after the homogenization treatment and the 131 phase forms after the isothermal aging process. These two independent processes could be controlled by the precipitation temperature range. The significant increase in the elongation of the as-cast alloy after homogenization treatment is attributed to the disappearance of the coarse primary Mgs（Gd, Er, Zn） phase and the presence of the 14H-LPSO structure. The precipitation sequence of the investigated alloy is α-Mg（SSS）/β″（D019）/β′（cbco）/β. Furthermore, the yield tensile strength （YTS） and ultimate tensile strength （UTS） values of the isothermal aging alloy have a great improvement, which could be attributed to the high density of the precipitated β′ phase.
基金financially supported by the National Natural Science Foundation of China(Nos.51771115,51775334 and 51821001)the National Science and Technology Major Project(No.2017ZX04006001)+1 种基金the National Key R&D Program of China(Grant No.2016YFB0701205)the Joint Fund for Space Science and Technology(No.6141B06300401)。
文摘In this work,the effects of Zn content(0-2 wt%)on microstructural evolution and mechanical properties of cast Mg-10Gd-3.5Er-0.5Zr alloys are studied.The results show that the as-cast Mg-10Gd-3.5Er-xZn-0.5Zr alloys are mainly composed of Mg matrix and secondary(Mg,Zn)3(Gd,Er)phases distributed along grain boundaries.With the increase in Zn content,the volume fraction of secondary(Mg,Zn)3(Gd,Er)phases increases and the grains get refined.In the process of solid solution treatment,Zn addition can lead to the formation of long-period stacking ordered(LPSO)structures and the volume fraction of LPSO structures increases with Zn content.In addition,the Zn addition can reduce the vacancy formation energy and accelerate the diffusion rate of RE elements in Mg matrix.Because of the comprehensive effect of secondary phases and the accelerated diffusion rate,the base alloy and 2Zn alloy have less grain growth after solid solution treatment than that of the 0.5Zn alloy and 1 Zn alloy.The precipitation process is also accelerated by enhanced diffusion rate.At room temperature(RT),the strengthening effect of β’+β1 precipitates is more effective than that of LPSO structures,so the peak-aged 0.5Zn alloy exhibits the most excellent mechanical performance at RT,with yield strength of 219 MPa,ultimate tensile strength 296 MPa and elongation of 6.4%.While LPSO structures have stronger strengthening effect at elevated temperature than that of β’+β1 precipitates,so the 1Zn alloy and 2Zn alloy have more stable mechanical performance than that of the base alloy and 0.5Zn alloy with the increase in tensile temperature.
基金financially supported by the Projects of Beijing Municipal Science and Technology Commission (No. Z131100003213019)the Projects of Beijing Municipal Commission of Education (Nos. KM201110005001 and KM201310005001)Beijing Natural Science Foundation (No. 2144043)
文摘The microstructures of as-cast and as-solution Mg–12Gd–2Er–1Zn–0.6Zr alloys were investigated by optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, highresolution transmission electron microscopy（HRTEM）X-ray diffraction（XRD） and selected-area electron diffraction（SAED） in the present investigation. The results show that the primary eutectic phase Mg5（Gd, Er, Zn） and some flocculent features are found in the as-cast alloy; the SAED pattern indicates that these flocculent features are the dense areas of stacking faults. The 14H-LPSO structure precipitates in the temperature range of 673–793 K, and the volume fraction of 14H-LPSO structure increases with the extension of heating time; however, there is no precipitation of 14H-LPSO structure when the temperature reaches up to 803 K. In addition, the Mg5（Gd, Er, Zn） phase dissolves gradually along with the precipitation of 14H-LPSO structure.
