Nano-structured layers are fabricated on the surface of 1.0C-1.5Cr steel by using the surface mechanical attrition treatment(SMAT)technology,and the microstructures of the surface nano-crystallization layers are chara...Nano-structured layers are fabricated on the surface of 1.0C-1.5Cr steel by using the surface mechanical attrition treatment(SMAT)technology,and the microstructures of the surface nano-crystallization layers are characterized by means of X-ray diffraction(XRD)and transmission electron microscopy(TEM).The friction and wear properties are also investigated by a UMT-2 friction and wear tester.Experimental research has indicated that the average diameter of nanocrystalline grains in the surface layer after being treated for 15 min is in the range of 10-20 nm,and ferrite and cementite grains can not be identified by their morphologies.The wear-resistance of the specimen treated for 15 min has been doubled,compared with that of the matrix due to the grain refinement to a nano-sized scale.The lowest friction coefficient is 0.27,which is for the specimen treated for 30 min,resulting from the dissolution of the cementite phase and the formation of a relative homogenous structure.The SMAT technique for enhancing the wear-resistance of the 1.0C-1.5Cr steel has an optimum processing time,which is in the range of 15-30 min.The dominant wear mechanism of the specimen treated for 15 min changes from adhesive wear into particle wear.展开更多
Isothermal compression tests of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy were conducted at a Gleeble-1500 simulator in deformation temperature range of 1103–1243K, strain rate range of 0.01–5.00 s-1and height reduction ra...Isothermal compression tests of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy were conducted at a Gleeble-1500 simulator in deformation temperature range of 1103–1243K, strain rate range of 0.01–5.00 s-1and height reduction range of 50 %–70 %. The effects of processing parameters on morphology, grain size and contents of a and b phases were discussed based on the quantitative microstructure examination, and the detailed explanation was shown. The results show that b transformed matrix will obviously grow up at higher deformation temperature or lower strain rate because of low grain growth activation energies. The content of a phase will decrease at higher deformation temperature or higher strain rate due to the phase transformation. Some elongated a or b grains exist at higher strain rate, implying that the dominant softening mechanism is dynamic recovery. The effect of height reduction on b transformed matrix is negligible, but the height reduction has some effects on the morphology of primary a phase.展开更多
Tensile properties of a two phase γ Ti 47Al 1.5Cr 0.5Mn 2.8Nb alloy with a duplex microstructure were tested under strain rates ranging from 5×10 -5 to 5×10 -3 s -1 at temperatures from 1 123 K to 1 273 K. ...Tensile properties of a two phase γ Ti 47Al 1.5Cr 0.5Mn 2.8Nb alloy with a duplex microstructure were tested under strain rates ranging from 5×10 -5 to 5×10 -3 s -1 at temperatures from 1 123 K to 1 273 K. It was found that there exists approximately linear relationship between the flow stresses and the logarithm of the strain rate at different temperatures. The strain rate dependence was analyzed by thermal activation theory, and dislocation climbing has been identified as the rate controlling mechanism.展开更多
Mg-x(Ti0.9 Zr0.2 Mn1.5 Cr0.3)(x=20%,30%,40%) (mass fraction) composite powders were prepared by reactive ball milling with hydrogen and their hydrogen storage properties and microstructure were investigated by XRD,SEM...Mg-x(Ti0.9 Zr0.2 Mn1.5 Cr0.3)(x=20%,30%,40%) (mass fraction) composite powders were prepared by reactive ball milling with hydrogen and their hydrogen storage properties and microstructure were investigated by XRD,SEM and pressure-composition-temperature measurement.The results show that the composites have 3.83%-5.07%hydrogen capacity at 553 K and good hydrogenation kinetics,even at room temperature.Among them,the milled Mg-30%(Ti0.9Zr0.2Mn1.5Cr0.3)composite has the highest hydrogenation kinetics as it can quickly absorb 2.1%hydrogen at 373 K,3.5%in 2 000 s at 473 K,even 3.26%in 60 s at 553 K under 3 MPa hydrogen pressure.The improved hydrogenation properties come from the catalytic effect of Ti0.9 Zr0.2 Mn1.5 Cr0.3 particles dispersed uniformly on the surface of Mg particles.展开更多
The structure and magnetic properties of Gd2Fe15.5Cr1.5 compound were investigated by means of X-ray diffraction and magnetization measurements.The Gd2Fe15.5Cr1.5 compound had a rhombohedral Th2Zn17-type structure.The...The structure and magnetic properties of Gd2Fe15.5Cr1.5 compound were investigated by means of X-ray diffraction and magnetization measurements.The Gd2Fe15.5Cr1.5 compound had a rhombohedral Th2Zn17-type structure.The Curie temperature of Gd2Fe15.5Cr1.5 compound was about 570 K.This value was about 60 K higher than that of the mother compound Gd2Fe17.Negative thermal expansion was found in Gd2Fe15.5Cr1.5 compound in a broad temperature range 294-572 K by X-ray dilatometry.The coefficient of the average thermal expansion was =-3.87×10-6 K-1 in 294-512 K,and-1.58×10-5 in 512-572 K.The magnetostriction deformations from 294 to 532 K were calculated by means of the differences between the experimental values of the lattice parameters and corresponding values extrapolated from the paramagnetic range.The result showed that the spontaneous volume magnetostrictive deformation ωS decreased linearly from 4.73×10-3 to 0.11×10-3 with the temperature increasing from 294 to 532 K.The analysis showed that the ωS mainly came from the contribution of the spontaneous linear magnetostrictive λc along the c axis.展开更多
基金supported by the National High-Tech.R&D Program of China(the National 863 plans projects,Grant No.2007AA03Z352)
文摘Nano-structured layers are fabricated on the surface of 1.0C-1.5Cr steel by using the surface mechanical attrition treatment(SMAT)technology,and the microstructures of the surface nano-crystallization layers are characterized by means of X-ray diffraction(XRD)and transmission electron microscopy(TEM).The friction and wear properties are also investigated by a UMT-2 friction and wear tester.Experimental research has indicated that the average diameter of nanocrystalline grains in the surface layer after being treated for 15 min is in the range of 10-20 nm,and ferrite and cementite grains can not be identified by their morphologies.The wear-resistance of the specimen treated for 15 min has been doubled,compared with that of the matrix due to the grain refinement to a nano-sized scale.The lowest friction coefficient is 0.27,which is for the specimen treated for 30 min,resulting from the dissolution of the cementite phase and the formation of a relative homogenous structure.The SMAT technique for enhancing the wear-resistance of the 1.0C-1.5Cr steel has an optimum processing time,which is in the range of 15-30 min.The dominant wear mechanism of the specimen treated for 15 min changes from adhesive wear into particle wear.
基金financially supported by the National Natural Science Foundation of China (No. 51205318)the Fundamental Research Funds for the Central Universities (No. 3102014JCQ01016)the University Student’s Innovation Training Program (No. 201410699020)
文摘Isothermal compression tests of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy were conducted at a Gleeble-1500 simulator in deformation temperature range of 1103–1243K, strain rate range of 0.01–5.00 s-1and height reduction range of 50 %–70 %. The effects of processing parameters on morphology, grain size and contents of a and b phases were discussed based on the quantitative microstructure examination, and the detailed explanation was shown. The results show that b transformed matrix will obviously grow up at higher deformation temperature or lower strain rate because of low grain growth activation energies. The content of a phase will decrease at higher deformation temperature or higher strain rate due to the phase transformation. Some elongated a or b grains exist at higher strain rate, implying that the dominant softening mechanism is dynamic recovery. The effect of height reduction on b transformed matrix is negligible, but the height reduction has some effects on the morphology of primary a phase.
文摘Tensile properties of a two phase γ Ti 47Al 1.5Cr 0.5Mn 2.8Nb alloy with a duplex microstructure were tested under strain rates ranging from 5×10 -5 to 5×10 -3 s -1 at temperatures from 1 123 K to 1 273 K. It was found that there exists approximately linear relationship between the flow stresses and the logarithm of the strain rate at different temperatures. The strain rate dependence was analyzed by thermal activation theory, and dislocation climbing has been identified as the rate controlling mechanism.
基金Projects(20833009,20873148,U0734005) supported by the National Natural Science Foundation of ChinaProject(2010CB631303) supported by the National Basic Research Program of China+2 种基金Project(2009A11GX052) supported by Dalian Science and Technology Foundation,ChinaProject(KFJJ10-1Z) supported by the State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology,ChinaProject(Y4090507) supported by the Zhejiang Basic Research Program of China
文摘Mg-x(Ti0.9 Zr0.2 Mn1.5 Cr0.3)(x=20%,30%,40%) (mass fraction) composite powders were prepared by reactive ball milling with hydrogen and their hydrogen storage properties and microstructure were investigated by XRD,SEM and pressure-composition-temperature measurement.The results show that the composites have 3.83%-5.07%hydrogen capacity at 553 K and good hydrogenation kinetics,even at room temperature.Among them,the milled Mg-30%(Ti0.9Zr0.2Mn1.5Cr0.3)composite has the highest hydrogenation kinetics as it can quickly absorb 2.1%hydrogen at 373 K,3.5%in 2 000 s at 473 K,even 3.26%in 60 s at 553 K under 3 MPa hydrogen pressure.The improved hydrogenation properties come from the catalytic effect of Ti0.9 Zr0.2 Mn1.5 Cr0.3 particles dispersed uniformly on the surface of Mg particles.
基金Project supported by the National Natural Science Foundation of China (50871074,50971056)the Research Fund of Tianjin Education Committee (20090303)
文摘The structure and magnetic properties of Gd2Fe15.5Cr1.5 compound were investigated by means of X-ray diffraction and magnetization measurements.The Gd2Fe15.5Cr1.5 compound had a rhombohedral Th2Zn17-type structure.The Curie temperature of Gd2Fe15.5Cr1.5 compound was about 570 K.This value was about 60 K higher than that of the mother compound Gd2Fe17.Negative thermal expansion was found in Gd2Fe15.5Cr1.5 compound in a broad temperature range 294-572 K by X-ray dilatometry.The coefficient of the average thermal expansion was =-3.87×10-6 K-1 in 294-512 K,and-1.58×10-5 in 512-572 K.The magnetostriction deformations from 294 to 532 K were calculated by means of the differences between the experimental values of the lattice parameters and corresponding values extrapolated from the paramagnetic range.The result showed that the spontaneous volume magnetostrictive deformation ωS decreased linearly from 4.73×10-3 to 0.11×10-3 with the temperature increasing from 294 to 532 K.The analysis showed that the ωS mainly came from the contribution of the spontaneous linear magnetostrictive λc along the c axis.
