The effect of Friction stir process(FSP)parameters on the microstructure and mechanical properties of an extruded Mge2.0Nde0.3Zne1.0Zr(wt.%)alloy was investigated in this paper.The alloy was friction stir processed wi...The effect of Friction stir process(FSP)parameters on the microstructure and mechanical properties of an extruded Mge2.0Nde0.3Zne1.0Zr(wt.%)alloy was investigated in this paper.The alloy was friction stir processed with different passes:single-pass,three-pass and five-pass,under a tool rotation rate of 800μm and a traverse speed of 200 mm min^(-1).FSP results in remarkable grain refinement of the extruded alloy(average grain size w3.8 mm as 3 passes)and almost complete dissolution of the Mg_(12)Nd phase in the matrix.With the increase of pass,the average grain size in the stir zone(SZ)is decreased firstly and then increases.The Vikers hardness of SZs in all FSPed samples is higher than that of the parent material(PM).Tensile tests at room-temperature show that the tensile strengths of the stir zones along the FSP advancing direction are slightly lower than those of PM.However,the elongations are remarkably improved from 13.0%for PM to 24.5%for SZ FSPed with three-passes.These improved tensile properties are attributed to the microstructure refinement,dynamic recrystallization and dissolution of the Mg_(12)Nd phase.展开更多
The microstructure, microsegregation, and mechanical properties of directional solidified Mg–3.0Nd–1.5Gd ternary alloys were experimentally studied. Experimental results showed that the solidification microstructure...The microstructure, microsegregation, and mechanical properties of directional solidified Mg–3.0Nd–1.5Gd ternary alloys were experimentally studied. Experimental results showed that the solidification microstructure was composed of dendrite primary a（Mg） phase and interdendritic a（Mg） · Mg12（Nd, Gd） eutectic and Mg5 Gd phase. The primary dendrite arm spacing k1 and secondary dendrite arm spacing k2 were found to be depended on the cooling rate R in the form k1= 8.0415 9 10-6R-0.279 and k2= 6.8883 9 10-6R-0.205, respectively, under the constant temperature gradient of40 K/mm and in the region of cooling rates from 0.4 to 4 K/s. The concentration profiles of Nd and Gd elements calculated by Scheil model were found to be deviated from the ones measured by EPMA to varying degrees, due to ignorance of the back diffusion of the solutes Nd and Gd within a（Mg） matrix. And microsegregation of Gd depended more on the growth rate, compared with Nd microsegregation. The directionally solidified experimental alloy exhibited higher strength than the non-directionally solidified alloy, and the tensile strength of the directionally solidified experimental alloy was improved,while the corresponding elongation decreased with the increase of growth rate.展开更多
Nd3＋ substituted spinel ferrites with formula MgxCd1-xNd0.03Fe1.97O4（x = 0.0.2,0.4,0.6.0.8 and 1.0）were prepared by oxalate co-precipitation method using novel microwave sintering technique. AR grade sulphates were...Nd3＋ substituted spinel ferrites with formula MgxCd1-xNd0.03Fe1.97O4（x = 0.0.2,0.4,0.6.0.8 and 1.0）were prepared by oxalate co-precipitation method using novel microwave sintering technique. AR grade sulphates were used as starting chemicals. The samples were sintered at optimized power of 70 W for10 min in a microwave oven（800 W）. The structural analysis of these samples was done by using X-ray diffraction, scanning electron microscope and Fourier transform IR techniques. The XRD analysis of the synthesized ferrite confirms the formation of cubic spinel structure of ferrite. The influence of Nd3＋substitution on various structural parameters of Mg-Cd ferrites was reported. IR study indicates the spectra contain two intense absorption bands around 600 and 400 cm^（-1） in addition with four extra bands. The magnetic properties of all ferrites were studied by using a vibration sample magnetometer.The crystallite and grain size dependant magnetic properties are observed. The composition Mg_（0.6）Cd_（0.4）Nd_（0.03）Fe_（1.97）O_4 has better magnetic properties that can be used in recording media. The fast synthesis of spinel ferrites is yielded due to use of the microwave sintering technique.展开更多
Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.TNd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy.In the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener...Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.TNd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy.In the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener,having base centered orthorhombic structure with its lattice constants of a-（β″）=0.64 nm,b-（β″）=2.22 nm, and c-（β″）=0.52 nm was identified.In the case of Mg-Nd-Zr alloy aged at 250℃,the presence ofβ″andβ′phases was identified.The crystal structure ofβ″phase was found to be DO-（19） and its orientation relationships with Mg matrix were [0001]-（β″）//[0001]-（Mg） and [01（？）0]-（β″）//[01（？）0]-（Mg）.Theβ′phase had face centered cubic structure and its orientation relationships with Mg matrix were [011]-（β′）//[0001]-（Mg） and [（？）1（？）]β′//[（？）110]）-（Mg）. The Mg-2.TNd-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.展开更多
基金This work is supported by Shanghai Phospherus Program(Project No.11QH1401200)Program for New Century Excellent Talents in University by Ministry of Education of China(Project No.NCET-11-0329).
文摘The effect of Friction stir process(FSP)parameters on the microstructure and mechanical properties of an extruded Mge2.0Nde0.3Zne1.0Zr(wt.%)alloy was investigated in this paper.The alloy was friction stir processed with different passes:single-pass,three-pass and five-pass,under a tool rotation rate of 800μm and a traverse speed of 200 mm min^(-1).FSP results in remarkable grain refinement of the extruded alloy(average grain size w3.8 mm as 3 passes)and almost complete dissolution of the Mg_(12)Nd phase in the matrix.With the increase of pass,the average grain size in the stir zone(SZ)is decreased firstly and then increases.The Vikers hardness of SZs in all FSPed samples is higher than that of the parent material(PM).Tensile tests at room-temperature show that the tensile strengths of the stir zones along the FSP advancing direction are slightly lower than those of PM.However,the elongations are remarkably improved from 13.0%for PM to 24.5%for SZ FSPed with three-passes.These improved tensile properties are attributed to the microstructure refinement,dynamic recrystallization and dissolution of the Mg_(12)Nd phase.
基金financially supported by the National Natural Science Foundation of China (No. 51071129)the Special Funds of the National Natural Science Foundation of China (No. 51227001)
文摘The microstructure, microsegregation, and mechanical properties of directional solidified Mg–3.0Nd–1.5Gd ternary alloys were experimentally studied. Experimental results showed that the solidification microstructure was composed of dendrite primary a（Mg） phase and interdendritic a（Mg） · Mg12（Nd, Gd） eutectic and Mg5 Gd phase. The primary dendrite arm spacing k1 and secondary dendrite arm spacing k2 were found to be depended on the cooling rate R in the form k1= 8.0415 9 10-6R-0.279 and k2= 6.8883 9 10-6R-0.205, respectively, under the constant temperature gradient of40 K/mm and in the region of cooling rates from 0.4 to 4 K/s. The concentration profiles of Nd and Gd elements calculated by Scheil model were found to be deviated from the ones measured by EPMA to varying degrees, due to ignorance of the back diffusion of the solutes Nd and Gd within a（Mg） matrix. And microsegregation of Gd depended more on the growth rate, compared with Nd microsegregation. The directionally solidified experimental alloy exhibited higher strength than the non-directionally solidified alloy, and the tensile strength of the directionally solidified experimental alloy was improved,while the corresponding elongation decreased with the increase of growth rate.
文摘Nd3＋ substituted spinel ferrites with formula MgxCd1-xNd0.03Fe1.97O4（x = 0.0.2,0.4,0.6.0.8 and 1.0）were prepared by oxalate co-precipitation method using novel microwave sintering technique. AR grade sulphates were used as starting chemicals. The samples were sintered at optimized power of 70 W for10 min in a microwave oven（800 W）. The structural analysis of these samples was done by using X-ray diffraction, scanning electron microscope and Fourier transform IR techniques. The XRD analysis of the synthesized ferrite confirms the formation of cubic spinel structure of ferrite. The influence of Nd3＋substitution on various structural parameters of Mg-Cd ferrites was reported. IR study indicates the spectra contain two intense absorption bands around 600 and 400 cm^（-1） in addition with four extra bands. The magnetic properties of all ferrites were studied by using a vibration sample magnetometer.The crystallite and grain size dependant magnetic properties are observed. The composition Mg_（0.6）Cd_（0.4）Nd_（0.03）Fe_（1.97）O_4 has better magnetic properties that can be used in recording media. The fast synthesis of spinel ferrites is yielded due to use of the microwave sintering technique.
基金National Basic Research Program of China(50874079)Natural Science Foundation of Shanxi Province(2006011053)Taiyuan Science and Technology Project(100115105)
文摘Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.TNd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy.In the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener,having base centered orthorhombic structure with its lattice constants of a-（β″）=0.64 nm,b-（β″）=2.22 nm, and c-（β″）=0.52 nm was identified.In the case of Mg-Nd-Zr alloy aged at 250℃,the presence ofβ″andβ′phases was identified.The crystal structure ofβ″phase was found to be DO-（19） and its orientation relationships with Mg matrix were [0001]-（β″）//[0001]-（Mg） and [01（？）0]-（β″）//[01（？）0]-（Mg）.Theβ′phase had face centered cubic structure and its orientation relationships with Mg matrix were [011]-（β′）//[0001]-（Mg） and [（？）1（？）]β′//[（？）110]）-（Mg）. The Mg-2.TNd-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.
