Microstructure and phase forming process of Al-3Ti-0.2C-1RE grain refiner

An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.

Phase formation with NaZn_(13) structure in metamagnetic La(Fe_(1–x)Co_x)_(11.9)Si_(1.1) compounds

The effects of different annealing conditions on the phase formation with NaZn13 structure were investigated in La（Fe1-xCox）11.9Si1.1 （x=0.068） compounds. It was found that the 1：13 phase was not formed directly from the melt upon cooling but via a peritectic reaction between the pro-peritectic γ-Fe and the La-rich phase. Annealing temperature was very important for the formation of 1：13 phase. Ice water was confirmed to be a preferable quenching medium. La（Fe1-xCox）11.9Si1.1 （x=0.068） compounds with almost single 1：13 phase were obtained at 1473 K after 15 d.

Phase relationships in the Yb-Fe-Sb system at 530 ℃

Phase relationships in the Yb-Fe-Sb ternary system at 530 °C were investigated mainly by powder metallurgy and X-ray powder diffraction.Nine binary compounds（Yb6Fe23, Yb2Fe17, FeSb, FeSb2, YbSb2, YbSb, Yb11Sb10, Yb4Sb3, and αYb5Sb3） and one ternary compound（Fe4YbSb12） were confirmed in this system at 530 °C.The homogeneity range of FeSb phase extended from approximately 43at.%Sb to 45at.%Sb, the maximum solid solubility of Sb in Fe phase and Yb in FeSb phase was approximately 3at.%Sb and 1at.%Yb at 530 °C, respectively.Isothermal section of the phase diagram of the Yb-Fe-Sb ternary system at 530 °C consisted of thirteen single-phase regions, twenty-four two-phase regions, and twelve three-phase regions.

Highly nonlinear property and threshold voltage of Sc_2O_3 doped ZnO-Bi_2O_3-based varistor ceramics

A series of ZnO-Bi2O3-based varistor ceramics doped with 0-0.4 mol.% Sc2O3 were prepared by high-energy ball milling and sintered at temperatures between 1000 and 1150oC. X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were applied to characterize the phases and microstructure of the varistor ceramics. A DC parameter instrument for varistor ceramics was applied to investigate the electronic properties and V-I characteristics. The results showed that there were no changes in crystal structure with Sc2O3-doped varistor ceramics and that the average size of ZnO grain increased first and then decreased. The best electronic characteristics of the varistor ceramics prepared by high-energy ball milling were found in 0.3 mol.% Sc2O3-doped ZnO-Bi2O3 -based ceramics sintered at 1000 oC, which exhibited a threshold voltage of 821 V/mm, nonlinear coefficient of 62.1 and leakage current of 0.16 μA.

Microstructure and electrical resistivity in the GdNi_(5–x)Cu_x intermetallic series

The effect of the Ni/Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi5-xCux series was studied. The value of temperature of phase transition（T_（ph）） estimated from temperature dependence of electrical resistance varied non-linearly across copper doping from 32.5 K（x=0.0） to 29.1 K（x=5.0）. The value of residual resistivity（ρo） estimated at low temperature range decreased from 27.28 μΩcm（x=0.0） to 9.44 μΩcm（x=5.0）, which was discussed as the influence of microstructure. In order to describe the temperature dependence of resistivity ρ（T） a variety of approaches were applied due to different scattering mechanisms occurring at high and low temperature ranges. The change within ρ（T） curvature was evidenced at low temperature range across copper doping. The temperature variation of the resistivity was quite peculiar for Cu-rich compounds（x=4.8, x=5.0）, which might be correlated with the incommensurate magnetic structure derived from the weakly negative interaction between the nearest neighbours of Gd. The correlation between microstructure and resistivity was observed.

Effect of Al_(82.8)Cu_(17)Fe_(0.2) alloy doping on structure and magnetic properties of SmCo5-based ribbons

This work tries to improve the magnetic properties by multi-element doping in the form of a ternary alloy.SmCo_(5+)χwt%Al-Cu-Fe(x=0-7)ribbons melt-spun at 40 m/s were produced by adding Al_(82.8)Cu_(17)Fe_(0.2)alloy into SmCo_(5) matrix,and their phases,microstructure,and magnetic properties were investigated.The results show that both x=0 and 3 ribbons form a cellular microstructure.Al-Cu-Fe addition reduces the content of the Sm_(2)(Co,M)_(7) cell wall,narrows its width,and forms the local disordered micro-regions and solute-segregation nanoclusters in the Sm(Co,M)_(5) grains.With x increasing to5,Al-Cu-Fe addition promotes the phase separation between and within grains of the SmCo_(5)-based alloy.The Al-Cu-Fe addition can simultaneously improve the coercivity and magnetization of the SmCo_(5)-based ribbons,in particular,the magnetization of the x=3 ribbons increases by 35%,while the coercivity of the x=5 ribbons increases by 3.9 times.Finally,the microstructure evolution models are built up,and the relationship between the microstructure and the magnetic properties is discussed.