A γ-TiAl base alloy with the composition of Ti-34Al-2Mn（wt--%）was prepared by consum-able electrode arc-melting technique.The effect of homogenization processing following arc-melt-ing on its microstructure and mec...A γ-TiAl base alloy with the composition of Ti-34Al-2Mn（wt--%）was prepared by consum-able electrode arc-melting technique.The effect of homogenization processing following arc-melt-ing on its microstructure and mechanical properties was investigated.The emphases were placedon the microstructural evolution during solidification and homogenization,and the relationship be-tween microstructure and ductility.It has been determined that the samples annealed at 900℃for 20 h exhibit the best ductility compared with those treated at other temperatures up to 1100℃,and they have a mixed structure of equiaxed grain of γ-TiAl single phase and some prima-ry lamellar grains which include three types of interfaces,i.e.,α<sub>2</sub>/γ,/γ/γ<sub>S</sub>,γ/γ<sub>T</sub>,maintainingspecific orientaion relationships between both sides.The ductility improvement is believed to be as-sociated with existence of suitable amount of α<sub>2</sub>-Ti<sub>3</sub>Al phase and the refinement of grains ob-tained at 900℃.展开更多
Using density functional theory calculations, we investigate the tetragonal distortion, electronic structure and magnetic property of Pt2MnSn. The results indicate that, when the volume-conserving tetragonal distortio...Using density functional theory calculations, we investigate the tetragonal distortion, electronic structure and magnetic property of Pt2MnSn. The results indicate that, when the volume-conserving tetragonal distortion occurs, the energy minimum appears at c/a = 0.84, and the energy difference between the minimum and cubic phase is as high as 107 me V/f. u. Thus from the point of view of thermodynamics, martensitie transformation may occur in Pt2MnSn with decreasing the temperature. The electronic structure of its cubic and martensitic phases also approves this. Moreover, both the cubic and tetragonal phases of Pt2MnSn are ferromagnetic structures and their total magnetic moments are 4.26 μB and 4.12 μB, respectively.展开更多
Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resista...Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resistance ofthe as-welded Cu12Mn8Al3Fe2Ni alloy is much more superior to that of the as-cast one. The cumulative mass lossand the mass loss rate of the as-welded Cu12Mn8Al3Fe2Ni alloy are almost 1/4 that of the as-cast one. SEM analysisof eroded specimens reveals that the as-cast Cu12Mn8Al3Fe2Ni alloy is attacked more severely than the as-weldedone. Microcracks causing cavitation damage initiate at the phase boundaries.展开更多
High efficient lead halide perovskites with wide-color gamut properties have emerged as new candidates for backlight displays.However,the toxicity of lead and the instability of halide perovskites greatly limit their ...High efficient lead halide perovskites with wide-color gamut properties have emerged as new candidates for backlight displays.However,the toxicity of lead and the instability of halide perovskites greatly limit their practical applications.Herein,the luminescent powders of[(CH_(3))4N]2MnBr_(4)and[(CH_(3))4N]MnBr3 were synthesized via a simple yet robust solvent evaporation method.[(CH_(3))4N]2MnBr_(4)with tetrahedral coordination Mn^(2+)and[(CH_(3))4N]MnBr3 with octahedral coordination Mn^(2+)show green at 517 nm and red emission peaks at 620 nm,respectively,originating from the^(4)T1-^(6)A_(1)transition of Mn^(2+).To enhance optical of manganese halide via effective alloying,Zn^(2+)-doped[(CH_(3))4N]2MnBr_(4)was successfully prepared,and the quantum efficiency of[(CH_(3))_(4)N]_(2)Mn_(0.6)Zn_(0.4)Br_(4)was as high as 65%.Furthermore,[(CH_(3))4N]2Mn0.6Zn0.4Br_(4)exhibits better optical and thermal stability compared to[(CH_(3))4N]2MnBr_(4).[(CH_(3))_(4)N]_(2)Mn_(0.6)Zn_(0.4)Br_(4)@CsPbBr_(1.2)I_(1.8)light conversion films with different green-to-red ratios are placed in backlight display devices,and their color gamut exceeds 106%of the National Television Standards Committee(NTSC)1953 standard,which is superior to the currently reported Mn-based perovskite.This work broadly shows that the[(CH_(3))_(4)N]_(2)Mn_(0.6)Zn_(0.4)Br_(4)will provide effective route to fabricate stable and high-performance lead-free liquid crystal displays.展开更多
In this work, the corrosion behavior of the ascast and extrusion and aging treatment Mg–2Zn–0.2Mn alloy in simulated body fluid(SBF) were studied. The wear behavior of Mg–2Zn–0.2Mn alloy was investigated using pin...In this work, the corrosion behavior of the ascast and extrusion and aging treatment Mg–2Zn–0.2Mn alloy in simulated body fluid(SBF) were studied. The wear behavior of Mg–2Zn–0.2Mn alloy was investigated using pin-on-disk technique and stainless steel as counterbody under a constant sliding velocity at different loads ranging from 2 to 5 N with deionized water and SBF as lubrication.The results showed that the extrusion and aging treatment Mg–2Zn–0.2Mn alloy exhibited better corrosion resistance compared with the as-cast alloy due to finer average grain size, more homogeneous phase distribution, and decrease in porosity. The friction coefficient of fractional pair under SBF and deionized water lubrication were obviously lower than that of dry sliding condition. However, the wear rate of Mg–2Zn–0.2Mn alloy under SBF lubrication was higher than that of dry sliding and deionized water lubrication due to the corrosiveness of SBF accelerated the wear of the magnesium alloy. The magnesium alloy exhibited different wear mechanisms with the variety of loads and lubrication conditions.展开更多
Fine-grained W-Ni-Mn-YOalloys were fabricated by mechanical alloying-assisted spark plasma sintering(SPS), and the effects of YOcontent on the microstructure and mechanical properties of the alloys were studied. Fine-...Fine-grained W-Ni-Mn-YOalloys were fabricated by mechanical alloying-assisted spark plasma sintering(SPS), and the effects of YOcontent on the microstructure and mechanical properties of the alloys were studied. Fine-grained 90 W-6 Ni-4 Mn-YOalloys with uniform microstructure and excellent properties were prepared by SPS at 1150 ℃. The addition of trace YOinhibited the sintering densification process and refined the W grain size. The average W grain size decreased from 5.5 μm to 2.1 μm.The fracture mode changed from W grain transgranular fracture and W-W interface fracture to W-W and W-Matrix phase interface fracture. The Rockwell hardness and bending strength of alloys initially increased and then decreased with increasing YOcontent. The optimum comprehensive mechanical properties(Rockwell hardness and bending strength) of the alloys were obtained at the same time when the mass fraction of YOwas 0.4%.展开更多
This study examines the relationship among cooling rate,microstructure and mechanical properties of a sand-casted Al-5.0 Mg-0.6 Mn-0.25 Ce(wt%)alloy subjected to T4 heat treatment(430℃×12 h+natural aging for 5 d...This study examines the relationship among cooling rate,microstructure and mechanical properties of a sand-casted Al-5.0 Mg-0.6 Mn-0.25 Ce(wt%)alloy subjected to T4 heat treatment(430℃×12 h+natural aging for 5 days),and the tested alloys with wall thickness varying from 5 to 50 mm were prepared.The results show that as the cooling rate increases from0.22 to 7.65 K/s,the average secondary dendritic arm spacing(SDAS,λ2)decreases from 94.8 to 27.3μm.The relation between SDAS and cooling rate can be expressed by an equation:λ2=53.0 Rc-0345.Additionally,an increase in cooling rate was shown not only to reduce the amount of the secondary phases,but also to promote the transition from Al10 Mn2 Ce toα-Al24(Mn,Fe)6Si2 phase.Tensile tests show that as the cooling rate increases from 0.22 to 7.65 K/s,the ultimate tensile strength(UTS)increases from 146.3 to 241.0 MPa and the elongation(EL)increases sharply from 4.4 to 12.2%for the ascast alloys.Relations of UTS and EL with SDAS were determined,and both the UTS and EL increase linearly with(1/λ2)0.5and that these changes can be explained by strengthening mechanisms.Most eutectic Al3Mg2 phases were dissolved during T4 treatment,which in turn further improve the YS,UTS and EL.However,the increment percent of YS,UTS and EL is affected by the cooling rate.展开更多
基金Supported by National Advanced Materials Committee of China
文摘A γ-TiAl base alloy with the composition of Ti-34Al-2Mn（wt--%）was prepared by consum-able electrode arc-melting technique.The effect of homogenization processing following arc-melt-ing on its microstructure and mechanical properties was investigated.The emphases were placedon the microstructural evolution during solidification and homogenization,and the relationship be-tween microstructure and ductility.It has been determined that the samples annealed at 900℃for 20 h exhibit the best ductility compared with those treated at other temperatures up to 1100℃,and they have a mixed structure of equiaxed grain of γ-TiAl single phase and some prima-ry lamellar grains which include three types of interfaces,i.e.,α<sub>2</sub>/γ,/γ/γ<sub>S</sub>,γ/γ<sub>T</sub>,maintainingspecific orientaion relationships between both sides.The ductility improvement is believed to be as-sociated with existence of suitable amount of α<sub>2</sub>-Ti<sub>3</sub>Al phase and the refinement of grains ob-tained at 900℃.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51301119,51301195,51171206 and 51401140the National Science Foundation for Young Scientists of Shanxi Province under Grant No 2013021010-1the Youth Foundation of Taiyuan University of Technology under Grant No 1205-04020102
文摘Using density functional theory calculations, we investigate the tetragonal distortion, electronic structure and magnetic property of Pt2MnSn. The results indicate that, when the volume-conserving tetragonal distortion occurs, the energy minimum appears at c/a = 0.84, and the energy difference between the minimum and cubic phase is as high as 107 me V/f. u. Thus from the point of view of thermodynamics, martensitie transformation may occur in Pt2MnSn with decreasing the temperature. The electronic structure of its cubic and martensitic phases also approves this. Moreover, both the cubic and tetragonal phases of Pt2MnSn are ferromagnetic structures and their total magnetic moments are 4.26 μB and 4.12 μB, respectively.
文摘Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resistance ofthe as-welded Cu12Mn8Al3Fe2Ni alloy is much more superior to that of the as-cast one. The cumulative mass lossand the mass loss rate of the as-welded Cu12Mn8Al3Fe2Ni alloy are almost 1/4 that of the as-cast one. SEM analysisof eroded specimens reveals that the as-cast Cu12Mn8Al3Fe2Ni alloy is attacked more severely than the as-weldedone. Microcracks causing cavitation damage initiate at the phase boundaries.
基金supported by the National Natural Science Foundation of China(Nos.51872207 and 52072271).
文摘High efficient lead halide perovskites with wide-color gamut properties have emerged as new candidates for backlight displays.However,the toxicity of lead and the instability of halide perovskites greatly limit their practical applications.Herein,the luminescent powders of[(CH_(3))4N]2MnBr_(4)and[(CH_(3))4N]MnBr3 were synthesized via a simple yet robust solvent evaporation method.[(CH_(3))4N]2MnBr_(4)with tetrahedral coordination Mn^(2+)and[(CH_(3))4N]MnBr3 with octahedral coordination Mn^(2+)show green at 517 nm and red emission peaks at 620 nm,respectively,originating from the^(4)T1-^(6)A_(1)transition of Mn^(2+).To enhance optical of manganese halide via effective alloying,Zn^(2+)-doped[(CH_(3))4N]2MnBr_(4)was successfully prepared,and the quantum efficiency of[(CH_(3))_(4)N]_(2)Mn_(0.6)Zn_(0.4)Br_(4)was as high as 65%.Furthermore,[(CH_(3))4N]2Mn0.6Zn0.4Br_(4)exhibits better optical and thermal stability compared to[(CH_(3))4N]2MnBr_(4).[(CH_(3))_(4)N]_(2)Mn_(0.6)Zn_(0.4)Br_(4)@CsPbBr_(1.2)I_(1.8)light conversion films with different green-to-red ratios are placed in backlight display devices,and their color gamut exceeds 106%of the National Television Standards Committee(NTSC)1953 standard,which is superior to the currently reported Mn-based perovskite.This work broadly shows that the[(CH_(3))_(4)N]_(2)Mn_(0.6)Zn_(0.4)Br_(4)will provide effective route to fabricate stable and high-performance lead-free liquid crystal displays.
基金financially supported by the National Natural Science Foundation of China (Nos. 51271131 and 51071108)
文摘In this work, the corrosion behavior of the ascast and extrusion and aging treatment Mg–2Zn–0.2Mn alloy in simulated body fluid(SBF) were studied. The wear behavior of Mg–2Zn–0.2Mn alloy was investigated using pin-on-disk technique and stainless steel as counterbody under a constant sliding velocity at different loads ranging from 2 to 5 N with deionized water and SBF as lubrication.The results showed that the extrusion and aging treatment Mg–2Zn–0.2Mn alloy exhibited better corrosion resistance compared with the as-cast alloy due to finer average grain size, more homogeneous phase distribution, and decrease in porosity. The friction coefficient of fractional pair under SBF and deionized water lubrication were obviously lower than that of dry sliding condition. However, the wear rate of Mg–2Zn–0.2Mn alloy under SBF lubrication was higher than that of dry sliding and deionized water lubrication due to the corrosiveness of SBF accelerated the wear of the magnesium alloy. The magnesium alloy exhibited different wear mechanisms with the variety of loads and lubrication conditions.
基金Project supported by the National Natural Science Foundation of China(51464010,51461014)the Natural Science Foundation of Hainan Province(20165207)
文摘Fine-grained W-Ni-Mn-YOalloys were fabricated by mechanical alloying-assisted spark plasma sintering(SPS), and the effects of YOcontent on the microstructure and mechanical properties of the alloys were studied. Fine-grained 90 W-6 Ni-4 Mn-YOalloys with uniform microstructure and excellent properties were prepared by SPS at 1150 ℃. The addition of trace YOinhibited the sintering densification process and refined the W grain size. The average W grain size decreased from 5.5 μm to 2.1 μm.The fracture mode changed from W grain transgranular fracture and W-W interface fracture to W-W and W-Matrix phase interface fracture. The Rockwell hardness and bending strength of alloys initially increased and then decreased with increasing YOcontent. The optimum comprehensive mechanical properties(Rockwell hardness and bending strength) of the alloys were obtained at the same time when the mass fraction of YOwas 0.4%.
基金supported financially by the National Natural Science Foundation of China (No.51674166)
文摘This study examines the relationship among cooling rate,microstructure and mechanical properties of a sand-casted Al-5.0 Mg-0.6 Mn-0.25 Ce(wt%)alloy subjected to T4 heat treatment(430℃×12 h+natural aging for 5 days),and the tested alloys with wall thickness varying from 5 to 50 mm were prepared.The results show that as the cooling rate increases from0.22 to 7.65 K/s,the average secondary dendritic arm spacing(SDAS,λ2)decreases from 94.8 to 27.3μm.The relation between SDAS and cooling rate can be expressed by an equation:λ2=53.0 Rc-0345.Additionally,an increase in cooling rate was shown not only to reduce the amount of the secondary phases,but also to promote the transition from Al10 Mn2 Ce toα-Al24(Mn,Fe)6Si2 phase.Tensile tests show that as the cooling rate increases from 0.22 to 7.65 K/s,the ultimate tensile strength(UTS)increases from 146.3 to 241.0 MPa and the elongation(EL)increases sharply from 4.4 to 12.2%for the ascast alloys.Relations of UTS and EL with SDAS were determined,and both the UTS and EL increase linearly with(1/λ2)0.5and that these changes can be explained by strengthening mechanisms.Most eutectic Al3Mg2 phases were dissolved during T4 treatment,which in turn further improve the YS,UTS and EL.However,the increment percent of YS,UTS and EL is affected by the cooling rate.
