Effects of quenching conditions on crystallization behavior of amorphous Al90Ni5Ce5 alloys

X-ray diffraction and DSC were used to investigate the crystallization behavior of amorphous Al90Ni5Ce5 alloys at different quenching temperatures.All the amorphous Al90Ni5Ce5 alloys quenched at different temperatures crystallize by two stages.The first stage corresponds to FCC Al phase precipitating from the amorphous matrix.The crystallization onset temperature increases with increasing quenching temperature.The quenching temperature also influences the isothermal behaviors.At low quenching temperatures,the FCC Al precipitation is only through grain growth.At high quenching temperatures,the FCC Al precipitation is through growth of quenched-in Al unclei and nucleation and growth of new crystallites.The reason that the crystallization onset temperature varies with quenching temperature is likely as that the quenched-in Al nuclei decreases with increasing temperature.     

MAGNETIC PROPERTIES AND CRYSTALLIZATION OF RAPIDLY QUENCHED(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) ALLOYS

The Curie temperature increases but crystallization temperature decreases with the in-crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The averagemagnetic moment of Fe atoms is almost a constant.By X-ray diffraction and ther-momagnetic measurements,the crystalline phases of the alloys,an unknown phase andα-(Fe,Ga)besides Fe_3 B as major one,were identified.The relationship between roomtemperature coercive field and Ga.content was also studied.     

Crystallization and microstructure evolution of amorphous Al85Y4Nd4Ni7 alloy

The mixture model of Al85Y4Nd4Ni7 alloy in which a partially crystallized amorphous alloy is regarded as a nanocomposite of an Al nanoparticle and a remaining amorphous matrix is presented. Its evolution in the process of crystallization has been investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Mainly amorphous structure with α-Al nanocrystals embedded in the amorphous matrix has been revealed by melt spining the alloy. Crystallization is showed to occur in three stages: (I) crystallization of amorphous alloy and formation of A1NiY, A1NdNi and unknown crystalline phases, (2) formation of Al3Y and Al3Nd, and (3) formation of Al3Ni.     

Influence of Ce on microstructure and mechanical properties of LA141 alloys

LA141-（0-1.2）Ce alloys were prepared with vacuum induction melting method. The effects of Ce addition on the microstructure and mechanical properties of LA 141 alloys were studied. The microstructure and phases composition of these alloys were analyzed by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry. The mechanical properties of these alloys were measured with tensile tester. The results show that Ce has refining effect on the alloys. In the alloys, some Al2Ce compounds exist, which make the A1 content dissolved in a and β phases decrease and the hard brittle Mg17Al12 phase refined. The refining effect improves the mechanical properties of alloys. When Ce content is 0.9%（mass fraction）, the tensile strength reaches 206.8 MPa and the elongation is two times as high as that of LAl41 alloy. Due to the generation of Al2Ce, the content of Al solid soluted in β phase decreases resulting in the decrease of alloy hardness with the addition of Ce.     

Effects of Zr on crystallization kinetics of Pr—Fe—B amorphous alloys

The effects of Zr on crystallization kinetics of Pr-Fe-B amorphous alloys have been investigated by DTA and XRD methods.It was found that for Pr8Fe86-xZrxB6(x=0,1,2)amorphous alloys,the final crystallized mixture is α-Fe and Pr2Fe14B,and the metastable Pr2Fe23B3 phase occurs during crystallization of Pr8Fe86B6 amorphous alloy,not during crystallization of Pr8Fe86-xZrxB6(x=1,2)amorphous alloys,By analyzing the activation energy of crystallization,the formation of an α-Fe/Pr2Fe14B composite microstructure with a coarse grain size in annealed Pr8Fe86B6 alloy,is attributed to a difficult nucleation and an easy growth for both the α-Fe and Pr2Fe14B in the alloy.The addition of Zr can be used to change the crystallization behavior of the α-Fe phase in Pr-Fe-B amorphous alloy,which is helpful to reduce the grain size for the α-Fe phase.     

Effect of Zr addition on microstructures and mechanical properties of Ni-46Ti-4Al alloy

The microstructures and mechanical properties of Ni-(46-x)Ti-4Al-xZr (x = 0-8, at.%) alloys have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical tests. The results show that the Ni-Ti-Al-Zr alloys are composed of TiNi and (Ti, Al) 2 Ni with Zr as a solid solution element in both phases, and the third phase, (Zr, Ti, Al) 2 Ni, appears in Ni-40Ti-4Al-6Zr and Ni-38Ti-4Al-8Zr alloys. The compressive yield strength at room temperature increases with the increase of Zr content due to the solid-solution strengthening of Zr and precipitation strengthening of (Ti, Al, Zr) 2 Ni phase. However, the Ni-42Ti-4Al-4Zr alloy exhibits the maximum compressive yield strength at 873 and 973 K because of the softening of (Zr, Ti, Al) 2 Ni phase in the alloys with more Zr addition. The tensile stress-strain tests and the SEM fracture surface observations show that the brittle to ductile transition temperature of Ni-42Ti-4Al-4Zr alloy is between 873 and 923 K.     

Electrocatalytic activity and electrochemical hydrogen storage of Ni-La alloy prepared by electrodeposition from aqueous electrolyte

Ni-La alloy coating was prepared by electrodeposition. The effect of cathodic current density on the La content of the alloy coatings was discussed. It is found that the content of La in the alloy increases with increasing the cathodic current density. The microstructures and codeposition mechanism of Ni-La alloy coatings were investigated by means of X-ray diffraction (XRD) and cyclic voltammetry (CV). The results demonstrate that the Ni-La alloy is FCC and codeposited by the induced mechanism. The hydrogen evolution reaction (HER) on the electrodeposited Ni-La alloy electrodes in alkaline solution was evaluated by Tafel polarization curves. It is found that La-Ni alloy coating exhibites much higher exchange current density for HER than pure Ni electrode, and that the exchange current density increases with increasing the La content of alloys. The good electrocatalytic activity for HER of this Ni-La alloy is attributed to the synergism of the electronic structure of La and Ni. The electrodeposited La-Ni alloys have a certain dectrochemical hydrogen storage capacity of 34- 143 mAh/g, which increases with increasing the La content of alloys.     

Solidification characteristics of high Nb-containing γ-TiAl-based alloys with different aluminum contents

The effect of Al content on the microstructure and solidification characteristics of Ti–Al–Nb–V–Cr alloys in as-cast and isothermally treated states was investigated using X-ray diffraction(XRD), scanning electron microscopy(SEM) equipped with energy dispersive spectroscope(EDS), and transmission electron microscopy(TEM). The typical solidification characteristics are due to the joint influence of both the crystal temperature range and the solidification path. The wide crystallization temperature range contributes to obtaining coarse dendrites in the as-cast Ti47Al7Nb2.5V1.0Cr(at%) alloy solidifying through the peritectic reaction. The b-solidifying Ti46Al7Nb2.5V1.0Cr(at%) alloy with the narrow crystallization temperature range is attributed to the formation of a homogeneous finegrained microstructure. However, the crystallization temperature range of Ti48Al7Nb2.5V1.0Cr(at%) alloy is equivalent to that of Ti46Al7Nb2.5V1.0Cr alloy, but it is solidified by peritectic reaction, leading to the formation of finer dendrites.     

Research on fabricating Fe base amorphous alloy by bar plasma spraying

Since amorphous alloys have wider application, they can not be fabricated using the conventional cooling velocity. The bar material plasma spraying is adopted to fabricate, Fe base amorphous alloy in this investigation. The crystallization degree, microstructure, micro-hardness, composition, crystallization temperature of the amorphous alloy and the flying rules of the atomized particles in the process of the plasma spray are tested. The results show that the alloy prepared has the high amorphous degree and homogeneous microstructure, micro-hardness and the crystallization temperature can reach 1 187 HV and 531 ℃ respectively. The atomization is very well during the process of plasma spraying; and there is high thermal gradient, the cooling velocity reaches 6.07 × 10^7 K/s.     

Microstructure and martensitic transformation behavior of Ni56-xMn25FexGa19 shape memory alloys简

Microstructure, martensitic transformation behavior, mechanical and shape memory properties of Ni56-x Mn25 Fex Ga19(x = 0, 2, 4, 6, 8) shape memory alloys were investigated using optical microscopy(OM), X-ray diffraction analysis(XRD), differential scanning calorimeter(DSC), and compressive test. It is found that these alloys are composed of single non-modulated martensite phase with tetragonal structure at room temperature, which means substituting Fe for Ni in Ni56 Mn25 Ga19 alloy has no effect on phase structure. These alloys all exhibit a thermoelastic martensitic transformation between the cubic parent phase and the tetragonal martensite phase. With the increase of Fe content, the martensitic transformation peak temperature(Mp) decreases from 356 °C for x = 0 to 20 °C for x = 8, which is contributed to the depressed electron concentration and tetragonality of martensite. Fe addition remarkably reduces the transformation hysteresis of Ni–Mn–Ga alloys. Substituting Fe for Ni in Ni56 Mn25 Ga19 alloy can decrease the strength of the alloys and almost has no influence on the ductility and shape memory property.     

Effects of TM on stability of structure corresponding to prepeak of amorphous Al_(90)TM_5Ce_5 Alloys

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Fragility and glass forming ability of Al-Ni-Ce alloy melts

The fragility of Al-Ni-Ce alloy melts with three kinds of different compositions, Al85Ni10Ce5,Al85Ni8Ce7, Al85Ni5Ce10 (mole fraction, %), was studied using oscillating-vessel viscometer and differential scanning calorimetry. Their fragility parameters obtained from experiments and theoretic calculation are: 238, 228 and 335 respectively. The results indicate that these three kinds of Al-Ni-Ce alloy melts are very fragile liquids, which kinetically show strong non-Arrhenius behaviour in the Angell plot, so they have poor glass forming ability (GFA).The alloy melt AI85NiSCe10 has the largest fragility parameter among the three alloy melts. In the preparation of rapidly quenched amorphous ribbons, AI85Ni10Ce5 and AI85Ni8Ce7 can gain amorphous ribbons when the rotate speed of the roller reaches 800r/min, while for Al85Ni5Ce10 it must exceed 1 000r/min.     

等温热处理对Zr57Cu15．4Ni12．6Al10Nb5块体非晶合金的组织结构与压缩性能的影响

对Zr57Cu15．4Ni12．6Al10Nb5块体非晶合金进行了等温热处理，用X射线衍射仪、扫描电镜、显微硬度计与压缩试验机研究了不同温度下的等温热处理后合金的组织结构变化、硬度变化与压缩性能变化。该非晶合金出现晶化的温度随热处理时间的增长而降低。在热处理时间相同的条件下，随热处理温度升高，合金的显微硬度有增大趋势。当非晶合金出现相分离或晶化时，其抗压缩强度将急剧下降，断裂方式由非晶态的断裂方式向晶态的断裂方式转变。     

Zr60Al15Ni25大块非晶合金晶化行为的原位XRD分析

利用差示扫描量热法(DSC)和原位X射线衍射法(In Situ XRD)研究了Zr<,60>Al<,15>Ni<,25>大块非晶合金的晶化行为.DSC研究结果表明,合金的玻璃转变温度Tg、品化开始温度Tx、晶化峰温度T<,p>分别为407.0℃、482.4℃和496.9℃,过冷液相区△Tx为75.4℃,合金具有良好的热...     

The compositional range of amorphous phase formation and thermal stability of Al90−xFe5Ni5Cex

The effects of Ce-substitution for Al in the Al_90−xFe₅Ni₅Ce_x (x = 0, 2, 5, 7, 8, 9, and 10) system on the mechanical alloying process were investigated. The structural evolution in these powders was characterized by scanning electron microscopy, differential thermal analysis and X-ray diffraction techniques. The compositional range of amorphous forming was obtained and it extended from 5 to 9 at.% Ce. With increasing Ce content, the crystallization temperature of amorphous alloys increases. The crystallization temperature versus concentration of Ce was reproduced well by applying an extension of a relationship between the crystallization temperature and the vacancy formation energy of constituents with smaller atomic radius. The crystallization product phases were analyzed by XRD after annealing the milled powders at temperature over the crystallization temperature.     

熔体结构变化对Al85Ni5Y8Co2非晶合金晶化行为的影响

采用四电极电阻法研究Al85Ni5Y8Co2合金熔体电阻率,并结合X射线衍射仪(XRD)和差示扫描量热仪(DSC)探索熔体结构变化对Al85Ni5Y8Co2非晶晶化行为的影响。结果表明:Al85Ni5Y8Co2合金在1135~1357 K温度区间内发生熔体结构变化,而熔体结构变化导致Al85Ni5Y8Co2非晶晶化行为存在差异;在熔体温度为1673 K下制备的非晶薄带第一晶化较1323 K和1523 K的明显提前,对激活能的计算证实其初晶化更容易析出FCC-Al,且更难析出Al2Y3、Al13Co4、Al9Co2和AlNi等脆性金属间化合物;通过XRD的测试发现高的熔体温度可能会导致熔体中原子团簇的破坏,从而引起非晶晶化行为的改变。     

Stability of electrodeposited amorphous Ni-Fe-P alloys

1Introduction Amorphous alloys possess many specific properties[1?3]and are used as functional materials extensively[4?6].They can be used as magnetic recording materials[7].When properly heated,their will precipitate as fine,dispersed,inter-metallic comp…     

Zr55Al10Cu30Ni5-xPdx块状非晶合金的玻璃形成能力和热稳定性

用铜模铸造方法制备了不同尺寸的Zr55Al10Cu30Ni5-xPdx(x=0,1,3,5)块状非晶合金，采用X射线衍射（XRD）、扫描差热分析（DSC）和透射电镜（TEM）分别为Zr55Al10Cu30Ni5-xPdx块状非晶样品的结构、热稳定性和微观组织进行了研究。结果表明：x=1时，合金具有最高的过冷液相区（高达100K）及最大的热稳定性，而对合金的玻璃形成能力影响不大，这说明用适量的Pd代表Zr55Al10Cu30Ni5合金中的Ni会提高合金的热稳定性；x=3时，合金的热稳定性有所提高，但降低了合金的玻璃形成能力；x=5时，非晶合金的热稳定性和玻璃形成能力同时降低。     

非晶合金的晶化动力学与初生相的内在联系

通过差示扫描量热法(DSC)研究了Zr60Al15Ni25非晶合金的晶化动力学。X射线衍射(XRD)和能谱(EDS)分析结果表明:Zr60Al15Ni25非晶合金晶化过程中的初生相为复杂三元化合物Al2NiZr6和AlNi4Zr5。非晶合金的有效晶化激活能反映了晶化初生相与非晶相间的结构差异,二者结构差异越大,有效晶化激活能就越高,Zr60Al15Ni25非晶合金的有效晶化激活能高达345 kJ/mol;当合金高温熔体快冷过程中的初生相与非晶合金的晶化初生相一致时,晶化动力学参数能够实际反映合金的玻璃形成能力,相反则不能。