Crystallization of amorphous Te-20 at.% Pb alloy obtained by rapid cooling from the liquid state

Crystallization of amorphous Te-20 at. % Pb alloy obtained by rapid cooling from the liquid state was investigated by differential thermal analysis, X-ray diffraction and transmission electron microscopy. It was found that crystallization, beginning at 337 K, is of a continuous nature and proceeds over a fairly wide temperature range. At the first crystallization stage, nucleation of the metastable phase MS I, with hexagonal structure and lattice parametersa = 4.49 Å andc = 5.85 Å, takes place. Contrasts observed in the micrographs of single crystals of phase MS I were interpreted as areas with increased concentration of Pb atoms. With rising temperature, the phase present in these areas dissolves, and in its place platelet precipitates of the compound PbTe appear. In this paper, a sequence of decomposition for the amorphous phase obtained in the Te-20 at. % Pb alloy, as well as a model for the precipitation of PbTe, are proposed.     

Dynamics and microstructural evolution of bulk amorphous Cu12.5Ni10Zr41Ti14Be22.5 during phase separations: a small-angle neutron scattering approach

Small-angle neutron scattering has been applied to investigate in detail the structural relaxation of bulk amorphous Cu_12.5Ni₁₀Zr₄₁Ti₁₄Be_22.5 alloy in the supercooled liquid range (620–673 K) and its effect on subsequent crystallization around the crystallization point (673 K). The interference events from typical phase separation were recorded as the alloy was annealed in the supercooled liquid range. It was revealed that the crystallization in the alloy which was previously relaxed in the supercooled liquid range was significantly prohibited, and further phase separation was observed. Considerable temperature dependence of these phase separations was observed. It has been demonstrated that the phase separation developed via the spinodal mode and the achieved microstructure consisted of one droplet-like supercooled liquid phase embedded in the similarly disordered matrix. The droplets showed a bar-like pattern and distributed in a relatively regular form in the matrix. The phase separations exhibited sluggish coarsening kinetics with much smaller exponent than the Lifshitz–Slyozov–Wagner value. However, the dynamic scaling property of the phase separations at different temperatures has been approved by our scaling analysis. This revised version was published online in November 2006 with corrections to the Cover Date.     

Ordering of the α-Fe(Si) Crystallization Phase in Annealed Fe_(73.5)Cu_1Mo_3Si_(13.5)B_9 Alloy

The ordering of the α-Fe(Si) crystallization phase in annealed Fe73.5Cu1Mo3Si13.5B9 alloy has been studied using XRD method. The α-Fe(Si) phase in Fe73.5Cu1Mo3Si13.5B9 alloy annealed at 460℃ for 1 h consists of the DO3-type ordered region with spherical shape and disordered region. The size of DO3 ordered region increases with the annealing temperature. When the annealing temperature is 560℃, the size of the ordered region in the α-Fe(Si) grain is 14.0nm,which is nearly as large as that of the α-Fe(Si) grain (14.2 nm) and the degree of order of the α-Fe(Si) phase is about 0.78. When Fe73.5Cu1 Mo3Si13.5B9 amorphous alloy is annealed at 520℃, with the increment of the annealing time, the shape of the DO3 ordered region in the α-Fe(Si) phase is spheroidal at the beginning of the annealing and becomes spherical and has asize of 12.8 nm when the annealing time is 60 min. In addition, the DO3 superlattice lines of the α-Fe(Si) phase will vanish if Fe73.5Cu1Mo3Si13.5 B9 amorphous alloy is annealed for 1 h at 750℃.     

Microstructure of Differently Annealed NanocrystallineFe_(72.7)Cu_1Nb_(1.8)Mo_2Si_(13)B_(9.5) Alloy

The microstructure of differently annealed nanocrystalline Fe72.7Cu1Nb1.8Mo2Si13B9.5 alloy was investigated by using Mssbauer spectroscopy and transmission electron microscope. The specimens were isochronally annealed at temperatures between 480℃ and 600℃ for 0.5 h. The experimental results show that the microstructure mainly consists of the nanoscale bcc α-Fe(Si) grains and the residual amorphous matrix phase. A trace paramagnetic phase was found for annealing about above 500℃. The volume fraction of cr-Fe(Si) grain increases with increasing annealing temperature, whereas the average size of grain is almost unchanged above 480℃ up to 580℃. The calculated thickness of the intergranular layer of the residual amorphous matrix clearly decreases with increasing annealing temperature.     

Crystallization of amorphous Te-20 at% Sn alloy

Amorphous Te-20 at% Sn alloy was obtained by rapid cooling from the liquid state. Phase transitions occurring during continuous heating of amorphous films were studied by differential thermal analysis, X-ray diffraction and transmission electron microscopy. It was found that the crystallization of the amorphous phase begins at 382 K and proceeds via nucleation and growth of metastable phases MS1 and MS2. The first of these phases was assigned the primitive cubic structure with lattice parameter a=3.2Å. The second phase, being a Te (Sn) solution, was assigned the hexagonal structure with lattice parameters a=4.45Å and c=5.85Å. During heating at 410 K the remaining amorphous phase decomposed into a mixture of Te crystals together with metastable phase MS3, which probably has the ZnS type structure with lattice parameter a=6.05Å. Within the temperature range 450 to 550 K the MS1 phase was transformed into SnTe, and the MS2 phase into Te. The metastable intermediate phase MS3 decomposed only near the solidus temperature, and the alloy attained its equilibrium structure.     

Effect of annealing on microstructure and mechanical properties of bulk nanocrystalline Fe3Al alloy with 5 wt.% Cu prepared by aluminothermic reaction

Microstructure and mechanical properties of bulk nanocrystalline Fe₃Al based alloy with 5 wt.% Cu prepared by aluminothermic reaction before and after annealed at 873, 1073 and 1273 K for 8 h were investigated. Microstructures of the alloy before and after the annealing consisted of a Fe-Al-Cu matrix, a little Al₂O₃ sphere and Fe₃AlC_x fiber phases. The matrix of the alloy before the annealing was composed a nanocrystalline phase with disordered bcc crystal structure and a little amorphous phase. The amorphous phase disappeared after the annealing and Fe₃Al phase with ordered DO₃ structure appeared in the alloy after annealed at 1073 and 1273 K in the matrix of the alloy. Size of the Fe₃AlC_x fiber phase increased with the annealing temperature. The alloy after the annealing had better plasticity, higher yield strength than that of the alloy before the annealing, and the alloy after annealed at 1273 K had the highest yield strength.     

Fe77Co2Zr9B10Cu2合金的制备及其磁性能

采用单辊快淬法制备了Fe77Co2Zr9B10Cu2合金,在530～750℃等温退火40 min,利用X射线衍射和振动样品磁强计研究了Fe77 Co2 Zr9 B10 Cu2合金的微观结构和磁性能。结果表明:淬态Fe77Co2Zr9B10Cu2合金为非晶、纳米晶双相结构。随着退火温度的升高,α-Fe晶体相从非晶、基体中析出,晶粒尺寸长大,晶化体积分数增加,矫顽力先减小后增大,比饱和磁化强度逐渐增大。实验结果表明,530℃退火后合金的矫顽力最小,在670℃时迅速增大。样品的磁性与其微观结构、晶粒尺寸、晶化体积分数等因素有关.     

等温退火对Alnico8合金微观结构的影响

利用透射电镜(TEM)和X射线小角衍射技术(SAXS)研究了磁场等温退火工艺参数对Alnico8合金的微观组织的影响,样本的晶格结构清晰可见。结果表明,在等温退火阶段Alnico8合金通过调幅分解形成两相结构,棒状的铁磁相(1α相)粒子高度有序地弥散在弱磁性相(2α相)当中。其中,1α相的平均长度由SAXS测得,并与TEM照片数据进行了验证比对。本文着重研究了1α相粒子平均长度随等温退火处理的温度及时间参数的改变规律,结果显示样本的磁性能与其微观结构有一定相关性。     

Isothermal decomposition of the ß′ phase in a Cu-Zn-Al alloy

The isothermal decomposition of theβ′ phase in a Cu-25 wt % Zn-6 wt % Al alloy was investigated using transmission electron microscopy and electron probe microanalysis. The ordering of theβ phase was too rapid to be suppressed during quenching from the solution annealing temperature. On ageing the alloy in the temperature range 603 to 703 K, theβ′ phase was found to decompose into a mixture of α+γ phases by the precipitation of fine and equiaxed γ-phase particles distributed uniformly throughout the matrix of α. The orientation relationship between α and γ was identified as $$\begin{gathered} (001)_\alpha ||(001)_\gamma \hfill \\ [010]_\alpha ||[010]_\gamma \hfill \\ \end{gathered} $$ The growth rate of the γ phase precipitates exhibited a maximum at 653 K. Electron probe microanalysis showed that the γ phase precipitates were enriched in aluminimum and depleted in zinc, compared to the α matrix. In addition to the uniform distribution of intragranular γ phase precipitates, heterogeneous precipitation of the α phase was observed along the grain boundaries indicative of a direct transformation ofβ′ to α in these regions: this reaction was found to be pronounced as the ageing temperature was increased up to 773 K.     

添加AlN对机械合金化Zr65Al7.5CU17.5Ni10非晶态合金热稳定性的影响

以成分为Zr65Al7.5Cu17.5Ni10的元素的粉末混合物及AIN颗粒为起始材料,经机械合金化形成非晶态合金为基体的复合材料,AIN添加量为5％－30％（体积分数,下同）,利用X射线衍射（XRD）,透射电子 显微镜（TEM）和差示扫描量热计（DSC）分析了含AIN复合材料的结构特性,玻璃转变与晶化行为,TEM观察表明,AIN第二相粒子弥散分布在晶Zr基合金基体上,粒子尺寸为20－200nm,仍为初始的晶体结构,与未添加AIN的Zr基非晶态合金相比,含5％－10％AIN的复合材料仍表现出较宽的过冷液态温度区域,玻璃转变温度（Tg)和晶化激活能（Ex)没有显著变化,但晶化起始温度（Tx)向高温移动大约10K,导致过冷液态温度区域的扩宽,AIN含量增至30％,明显的玻璃转变消失,Tx升高的20K。     

Formation of nanocrystalline structure during electron irradiation induced crystallization in amorphous Fe-Zr-B alloys

Effect of electron irradiation on the crystallization and phase stability of Fe₈₈Zr₉B₃ and Fe₇₁Zr₉B₂₀ amorphous alloys was examined. Electron irradiation at an accelerated voltage of 2000 kV was performed at room temperature. The Fe₇₁Zr₉B₂₀ alloy showed a wide supercooled liquid region and the ΔT_x value was 71 K, while no glass transition was observed in Fe₈₈Zr₉B₃ alloy. The amorphous phase in Fe–Zr–B alloys was not stable under irradiation and crystallization from the amorphous phase was accelerated by the irradiation. Nanocrystalline structure composed of α-Fe and cubic-Fe₂Zr was formed in Fe₈₈Zr₉B₃ alloy by irradiation induced crystallization, while no nanoscale precipitates of intermetallic compounds were formed during annealing. In Fe₇₁Zr₉B₂₀ alloy, the formation of nanocrystalline precipitates was also confirmed by irradiation induced crystallization, although the formation of nanocrystalline structure had not been realized in high B concentration Fe–Zr–B alloys by annealing. These new results show that electron irradiation is effective in producing a new nanocrystalline structure.     

Microstructure of the Ductile Phase in Intermetallic Compound Ni_(50)Al_(20)Fe_(30)

The microstructure of the single hot extruded and annealed Ni50Al20Fe30Y0.003 intermetallic compound alloys has been examined by means of high resolution electron microscopy (HREM). In these extruded and annealed alloys. the ductile phase is of a mixture of the disordered fcc γ matrix and or dered γ' precipitates. This fact well interprets the reason why the degree of annealing treatment can influence the strength and ductility of these alloys. The HREM observation revealed directly that there was some strain concentration at γ'-γ interfaces, due to the presence of more iron atoms in these two phases. The fixed orientation relationship between the γ phase and γ' precipitates was identified to be {001}γ{00 }γ' and <100 >γ < 100 > γ'     

Study on the microstructures and the magnetic properties of precipitates in a Cu75-Fe5-Ni20 alloy

The microstructural evolutions of precipitates formed in a Cu75-Fe5-Ni20 alloy on isothermal annealing at 873 K and 1073 K have been investigated by means of transmission electron microscopy (TEM). Nano-scale magnetic particles were formed randomly in the Cu-rich matrix after receiving a short annealing due to phase decomposition in the alloy. With increasing the isothermal annealing time, however, the striking features that two or more nano-scale particles with a cubic shape and a rod shape were aligned linearly along (100) directions were observed on isothermal annealing at 873 K and 1073 K, respectively. To investigate electro-magnetic properties of precipitates in a Cu-Fe-Ni alloy, the superconducting quantum interference device (SQUID) magnetometer and physical property measurement system (PPMS) were also complemented. The present study revealed significant influences that the magnetic properties of the specimens were closely related to the microstructures in the Cu-Fe-Ni alloy, which microstructures significantly depend on the isothermal annealing temperature.     

Microstructure and superconductivity in annealed Cu-Nb-(Ti,Zr, Hf) ternary amorphous alloys obtained by liquid quenching

Melt-quenched Cu-Nb-(Ti, Zr, Hf) ternary alloys have been found to be amorphous possessing high strength and good bend ductility. The niobium content in the amorphous alloys was limited to less than 35 at % and the titanium, zirconium or hafnium contents from 25 to 50 at %. The Cu₄₀Nb₃₀(Ti, Hf)₃₀ alloys showed a superconducting transition above the liquid helium temperature (4.2 K) after annealing at appropriate temperatures. The highest transition temperatures attained were 5.6 K for the Cu₄₀Nb₃₀Ti₃₀ alloy annealed for 1 h at 873 K and 8.4 K for the Cu₄₀Nb₃₀Hf₃₀ alloy annealed for 1 h at 1073 K. In addition, these alloys exhibited upper critical magnetic fields of 1.8 to 2.3×10⁶ Am^–1 at 4.2 K and critical current densities of 2×10³ to 1×10⁴ A cm^–2 at zero applied field and 4.2 K. Since the structure of the superconducting samples consisted of ordered phases based on a b c c lattice with a lattice parameter of 0.31 nm, it was concluded that the superconductivity in the Cu₄₀Nb₃₀Ti₃₀ and Cu₄₀Nb₃₀Hf₃₀ alloys was due to the precipitation of the metastable ordered b c c phases.     

热处理对(Fe_(0.52)Co_(0.30)Ni_(0.18))_(73)Cr_(17)Zr_(10)非晶合金的组织结构及磁性能的影响

采用单辊急冷法制备(Fe_(0.52)Co_(0.30)Ni_(0.18))_(73)Cr_(17)Zr_(10)非晶薄带,并对该合金进行等温退火。采用XRD,AFM,VSM研究退火温度对(Fe_(0.52)Co_(0.30)Ni_(0.18))_(73)Cr_(17)Zr_(10)非晶合金的组织结构和磁性能的影响。结果表明:非晶合金晶化过程为Am→α-Fe(Co)+Am′→α-Fe(Co)+Cr_2Ni_3+Fe_3Ni_2+Cr_2Zr+未知相。当退火温度Ti玻璃转变温度Tg时,由于结构弛豫、内应力的释放,合金的饱和磁化强度Ms有所提高;当晶化起始温度TxTi第一晶化峰值温度Tp1时,由于铁磁性α-Fe(Co)相的析出,Ms显著提升;当TiTp1时,由于晶粒长大和第二相的析出,Ms急剧恶化,565℃退火能够获得最好磁性能(Ms=106.8A·m~2·kg~(-1))。490℃和565℃退火后薄带表面的AFM观察表明,AFM图片所呈现的颗粒尺寸要比用Scherrer法测得的α-Fe(Co)纳米晶尺寸大得多,这是典型的包裹晶粒现象。     

Fe_(73.5)Cu_1Mo_3Si_(13.5)B_9超微晶软磁合金中薄层非晶相结构的X射线衍射研究

采甲X射线衍射法,针对Fr·:,(’u/M。罚、,:巳非晶合金,测定了不同退火温度下合金中薄层非晶相的短程有序范围和最近邻原子间距离等结构参数,并研究了这些参数与合金起始磁导率之间的关系,获得了使合金起始磁导率达最高值时薄层非晶相的结构参数范围。     

The formation, structure and properties of nanocrystalline Ni-Mo-B alloys

The structure, structure evolution and microhardness of nanocrystalline Ni-Mo-B alloys were studied by X-ray diffraction, differential scanning calorimetry, transmission and high resolution electron microscopy and microhardness measurements. The nanocrystalline structure was produced by controlled crystallization of amorphous alloys. The annealed samples consist of the FCC nanocrystals with the amorphous regions between them. The grain size of the nanocrystals is about 20 nm and depends on the chemical composition of the alloy. The chemical composition of the amorphous phase between the nanocrystals changes at the annealing. A slight grain growth was observed when the annealing time increases. The diffusion of Mo and B from FCC to the amorphous phase occurs at the annealing. It results in the lattice parameter change. The microhardness of the alloys increases during the annealing. The microhardness values are the same in all alloys before the nanocrystalline structure decomposition. The microhardness is inconsistent with the Petch-Hall equation. The microhardness of the alloys is determined by the microhardness of the amorphous phase bands located between the nanocrystalline grains.     

Nanocrystalline structure and initial permeability of annealed Fe73.5Cu1M03Si13.5B9 alloy

Abstract

The nanocrystalline structure of annealed Fe_73.5Cu₁M0₃Si_13.5B₉ alloy was investigated using X-ray diffraction and transmission electron microscopy. The relationship between the initial permeability and the microstructural parameters of the annealed alloy is discussed in this paper. The crystalline phase in annealed Fe_73.5Cu₁M0₃Si_13.5B₉ alloy is the α-Fe(Si) phase with a D0₃ superstructure. The volume fraction, silicon content, and degree of order of the α-Fe(Si) phase increased with an increase in the annealing temperature. In the temperature range of 460–560°C, the α-Fe(Si) phase had a grain size of 14 nm, and its grain number increased as the annealing temperature was increased. The D0₃ ordered region in the α-Fe(Si) grain was approximately spherical and its size increased as the annealing temperature increased. The size of the D0₃ ordered region was 14.0 nm at a temperature of 560°C, which is close to that of the α-Fe(Si) grain. There was an obvious change in the microstructure of the residual amorphous phase during annealing, the nearest atomic distance and the short range order of residual amorphous phase reaching a maximum and minimum respectively at 520°C. The initial permeability of annealed Fe_73.5Cu₁M0₃Si_13.5B₉ alloy was not only dependent on the microstructure of the α-Fe(Si) phase but was also related to the microstructural state of the residual amorphous phase.     

Structure and Magnetic Properties of Fe_(76.5)Si_(13.5)B_9Cu_1 Alloy with Nanoscale Grain Size

The structure and magnetic properties of Fe76.5Si13.5B9Cu1 alloys with a nanocrystalline (NC) bcc Fe(Si) phase trom about 23 to 46 nm in diameter, which were first formed into amorphous ribbons and then annealed at various temperatures between 703 and 773 K, have been investigated. At annealing temperatures from 703 to 748 K, the single NC bcc(Si) phase is obtained in the crystallized alloys. The grain size and the Si-content in the NC bcc Fe(Si) phase for the alloys annealed at different temperatures are presented. The soft magnetic properties and the saturation magnetostriction for the alloys with the NC bcc Fe(Si) phase are also measured. The results show that, the saturation magnetizotion and the permeability are improved for the alloys with only the NC bcc Fe(Si) phase and become better with decreasing of the NC bcc phase size, and the saturation magnetostriction declines for the alloys with increasing Si-content in the NC bcc Fe(Si) phase.