Mingtao WANG
,
B.Y.Zong
,
Gang WANG
材料科学技术（英）
A model has been established to simulate the realistic spatio-temporal microstructure evolution in recrystallization of a magnesium alloy using the phase field approach. A set of rules have been proposed to decide the real physical value of all parameters in the model. The thermodynamic software THERMOCALC is applied to determine the local chemical free energy and strain energy, which is added to the free energy density of grains before recrystallization. The Arrhenius formula is used to describe boundary mobility and the activity energy is suggested with a value of zinc segregation energy at the boundary. However, the mobility constant in the formula was found out by fitting to a group of grain size measurements during recrystallization of the alloy. The boundary range is suggested to decide the gradient parameters in addition of fitting to the experimental boundary energy value. These parameter values can be regarded as a database for other similar simulations and the fitting rules can also be applied to build up databases for any other alloy systems. The simulated results show a good agreement with reported experimental measurement of the alloy at the temperatures from 300 to 400℃ for up to 100 min but not at 250℃. This implies a mechanism variation in activity energy of the boundary mobility in the alloy at low temperature.
关键词:
Static recrystallization
,
null
,
null
,
null
Physics Letters A
The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(a)B(b)C(c))(y)D, in which A, B, C and D are four different magnetic ions and form four different sublattices, are studied by using the Ising model. And the Ising model was dealt with standard mean-field approximation. The regions of concentration in which two compensation points or one compensation point exit are given in c-a, b-c and a-b planes. The phase diagrams of the transition temperature T-c and compensation temperature T-comp are obtained. The temperature dependences of the magnetization are also investigated. Some of the result can be used to explain the experimental work of the molecule-based ferro-ferrimagnet ((NiaMnbFecII)-Mn-II-Fe-II)(1.5) [Cr-III (CN)6] - zH(2)O. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
mixed ferro-ferrimagnet;Ising model;four sublattices;phase diagram;transition temperature;compensation temperature;magnetic-properties;prussian blue;alloy
陈伟荣
,
王清
,
程旭
,
张庆瑜
,
董闯
金属学报
在三元Fe-B-Y合金系中, 以团簇线判据设计了5个基础合金成分, 即5条成分线Fe8B3-Y, Fe8B2-Y, Fe83B17-Y, Fe6B-Y和Fe9B-Y与一条团簇线Fe12Y-B的交点. 在此基础上加入微量Nb和M(M=Ti, Hf, Ta, Mo, Ni和Sn)形成五元合金, 用铜模铸造方法制备出直径为3 mm的合金棒. 考虑到元素B和Y在合金制备过程中的损耗, 对每个合金进行了成分修正.在M=Ti, Hf, Ta和Mo时, 能够形成块体非晶合金的三元基础成分均接近Fe8B3-Y与Fe12Y-B两条团簇线交点成分, 表明其对应的基础团簇为Archimedes八面体反棱柱Fe8B3. 最佳非晶成分为(Fe69.9B24.6Y5.5)96Nb2Ti2,其Tg=944 K, Tx=997 K, Trg=0.666.当M=Ni和Sn时, 均没有得到块体非晶合金.
关键词:
团簇线
,
Fe-based bulk metallic glass
,
composition design
陈伟荣
,
王清
,
程旭
,
张庆瑜
,
董闯
金属学报
doi:10.3321/j.issn:0412-1961.2007.08.003
在三元Fe-B-Y合金系中,以团簇线判据设计了5个基础合金成分,即5条成分线Fe8B3-Y,Fe8B2-Y,Fe83B17-Y,Fe6B-Y和Fe9B-Y与一条团簇线Fe12Y-B的交点.在此基础上加入微量Nb和M(M=Ti,Hf, Ta,Mo,Ni和Sn)形成五元合金,用铜模铸造方法制备出直径为3 mm的合金棒.考虑到元素B和Y在合金制备过程中的损耗,对每个合金进行了成分修正.在M=Ti,Hf,Ta和Mo时,能够形成块体非晶合金的三元基础成分均接近Fe8B3-Y与Fe12Y-B两条团簇线交点成分,表明其对应的基础团簇为Archimedes八面体反棱柱Fe8B3.最佳非晶成分为(Fe69.9B24.6Y5.5)96Nb2Ti2,其Tg=944 K,Tx=997 K,Trg=0.666.当M=Ni和Sn时,均没有得到块体非晶合金.
关键词:
团簇线
,
铁基块体非晶合金
,
成分设计
Journal of Applied Physics
The magnetic properties of R2Co14B1-xCx (x=0, 0.5 and R=Y, Sm) compounds have been studied by measuring the temperature dependence of the easy- and hard-magnetization curves on magnetically aligned samples between 1.5 and 300 K for Y2Co14(B,C) and at 4.2 K for Sm2Co14(B,C). The magnetic anisotropy of Y2Co14B increases due to the substitution of C for B, whereas the saturation magnetization decreases. Between 1.5 and 300 K, the anisotropy field of Y2Co14B0.5C0.5 increases about 2 T and the Co moment decreases about 0.05mu(B). The anisotropy field Of Sm2Co14B also increases upon C substitution and the saturation magnetization decreases slightly. The ac susceptibilities of both SM2Co14B and Sm2Co14B0.5C0.5 exhibit anomalies that may arise from a spin reorientation within the basal plane.
关键词:
nd2fe14b;exchange;nd2co14b;r2fe14b;field
Journal of Applied Physics
Y2Fe14B0.5C0.5 has the same tetragonal structure as Y2Fe14B with space group P4(2)/mnm. Magnetic properties of the Y2Fe14B0.5C0.5 compound have been studied using an extraction magnetometer with a maximum field of 6 T, in the temperature range from 1.5 to 300 K. By means of fitting the hard magnetization curves, the magnetocrystalline anisotropy constants K1, K2, and K3 were determined. It was found that although the magnetocrystalline anisotropy field (mu-0H-a) increases abnormally with increasing temperature as in the case of Y2Fe14B, the dependence of anisotropy constants on temperature is quite different from that of Y2Fe14B. K1 and K3 decrease slightly with increasing temperature. K2 increases abnormally with increasing temperature, which contributes to the abnormal dependence of anisotropy field on temperature. In addition, the substitution of carbon for boron leads to a reduction of 3d-3d interaction and spontaneous magnetization. In contrast, uniaxial anisotropy is increased by the addition of carbon below room temperature.
关键词:
alloys
杨广宇
,
刘咏
,
王岩
,
李建波
,
唐蓓
,
李慧中
中国有色金属学报
采用光学显微镜、扫描电镜及透射电镜研究微量B和Y对铸造Ti-AIl-Nb-W合金显微组织的影响.结果表明:Ti-47Al-4Nb-0.6W合金的基本凝固路线为L→β+L→(β+a)+L→(β+a)+γ→aa+γ→(a-γL)+γ→(a2+γ<,L>)+γ,添加微量B和Y并未改变其基本凝固路径;微量B元素在合金中以短棒状TiB2相存在,细化了铸造Ti-47Al-4Nb-0.6W合金的晶团尺寸及片层间距;微量稀土Y元素主要以Y2O3氧化物颗粒的形式分布于片层晶团界面处,在B和Y的共同作用下,合金的片层晶团尺寸以及片层间距进一步减小.
关键词:
TiAl基合金
,
显微组织
,
铸造合金
,
B
,
Y
Journal of Applied Physics
Magnetic properties and exchange couplings of nanocomposite (Nd,Y)(2)Fe(14)B/alpha-Fe magnets prepared by mechanical milling have been investigated at low temperatures. With decreasing temperature, due to Y substitution for Nd, an extension of the exchange coupling length in nanocomposite magnets occurs in a wider temperature range. This can be attributed a decreasing anisotropy of the hard-magnetic phase so that more soft-magnetic grains participate the exchange coupling. Close to 135 K, due to the spin reorientation, the hard magnetic phase is not more uniaxail, which leads to a drastic decrease of the magnetic properties of the Nd(2)Fe(14)B-based nanocomposite magnets. (C) 2003 American Institute of Physics.
关键词:
permanent-magnets;magnetocrystalline anisotropy;coercive field;grain-size;fe;remanence;phase;enhancement;dependence;ribbons
