Lattice-parameter misfits between the γ and γ′ phases in single crystals of nickel superalloys

X-ray diffractometry has been used to study the transformation of the profiles of X-ray diffraction lines (222), (004), (003) and to determine the values of the lattice misfit between the γ and γ′ phases (γ/γ′ misfit) for single crystals of nickel superalloys ZhS6U, ZhS30, ZhS32, VZhM1, and VZhM4 in the as-cast state and after heat treatment. It has been established that with an increase in the γ/γ′ misfit there increase tetragonal distortions of the fcc lattice of the γ solid solution. For the single crystals of VZhM4 alloyed with rhenium and ruthenium, splitting of the superlattice reflection of the strengthening γ′ phase has been revealed. The structural regularities revealed testify to qualitative changes in the factors that govern the redistribution of refractory alloying elements between the lattices of the γ and γ′ phases, for example, of Mo in the presence of Re and Ru.     

Special features of brazing VZhM4 and VZhM5 single crystal alloys

The processes of recrystallization of single crystal nickel creep-resisting alloys in brazing were investigated. The methods of preventing recrystallization of the single crystal alloys are described. The microstructure of the brazed joints in the VZhM4 and VZhM5 alloys is investigated. The effect of heat treatment on the microstructure of the brazed joints in the VZhM4 and VZhM5 alloys is described and the strength of the brazed joints determined.     

Effect of ruthenium on tensile properties of a single crystal Ni-based superalloy

The tensile properties of two single crystal Ni-based superalloys with and without added Ru (0 and 3 wt%) were investigated under a constant strain rate of 3.3×10^?4 /s at 20 °C, 760 °C, 800 °C and 1000 °C, respectively. The deformation mechanisms could be divided into two temperature regimes. From room temperature to 800 °C, the deformation mechanism is caused by the shearing of ?á? particles by anti-phase boundaries (APB) or stacking faults. At 1000 °C, the deformation mechanism is caused by the bypassing of ?á? particles by dislocations. At 20 °C and 800 °C, ?á? particles were sheared by APB. Due to smaller ?á? particles, the yield strength was decreased with addition of 3 wt% Ru. Additionally, work hardening is less pronounced in the alloy without Ru, hence the ultimate tensile strength was not decreased with the addition of 3 wt% Ru. At 760 °C, ?á? particles were sheared by stacking faults. Since the formation of stacking faults was promoted, the yield strength was decreased due to a 3 wt% Ru addition. However, the ultimate tensile strength was significantly increased when 3 wt% Ru was added. This is due to the markedly stronger work hardening caused by large numbers of stacking faults. At 1000 °C, deformation occurred by dislocations bypassing ?á? particles. Due to wider ?? channels, the yield strength was decreased by 3 wt% Ru addition. Moreover, Alloy 3Ru has smaller ?á? particles and a volume fraction as well as less pronounced work hardening, so the ultimate tensile strength was decreased when 3 wt% Ru was added.     

Effects of Platinum on the Hot Corrosion Behavior of Hf-Modified �á�-Ni3Al?+?��-Ni-Based Alloys

The establishment of a protective ??-Al₂O₃ scale is critical for providing high temperature protection from oxidation and hot corrosion, thereby improving lifetimes of advanced gas turbine engine components. Recent work by our group has shown that a wide range of Pt + Hf-modified ?á?-Ni₃Al + ??-Ni alloy compositions form a very adherent and slow-growing Al₂O₃ scale and exhibit excellent oxidation resistance. The main thrust of the present study was to understand the effects of Pt addition on the Type I (900 °C) and Type II (705 °C) hot corrosion (HC) behavior of model Hf-modified ?á? + ?? alloy compositions. The salt used to bring about hot corrosion was Na₂SO₄. It was found that the Type I HC resistance of ?á? + ?? alloys improved with up to about 10 at.% Pt addition, but then decreased significantly with increasing Pt content up to 30 at.% (the maximum level studied); however, under Type II HC conditions the resistance of ?á? + ?? alloys progressively improved with increasing Pt content up to 30 at.%. The effect of pre-oxidation on hot corrosion resistance was also examined, and the results indicated that pre-oxidation generally improved Type II HC resistance for the test duration studied.     

外延膜的高分辨X射线衍射分析

广泛应用于半导体、铁电和光电材料中的外延结构特征以及应变和缺陷会影响外延膜的物理/化学性能。高分辨X射线衍射是对外延结构进行无损准确表征的关键技术。本文从高分辨X射线衍射与外延结构倒易空间的关系出发,重点阐述高分辨X射线衍射与普通X射线衍射的联系与区别,以强调高分辨X射线衍射特征。以铁电外延膜与衬底结构高分辨X射线衍射为例,系统分析它们的高分辨X射线衍射斑特征,包括共格生长、非共格生长、倾斜生长下衍射斑特征,以及外延膜的尺寸、外延膜的倾斜扭转和外延膜的应变对衍射斑的影响等。结合Si1-xGex(x=0.1)等外延膜结构的具体分析阐述如何通过高分辨X射线衍射谱来获取外延膜结构参数,包括外延膜晶格常数、晶格错配度以及厚度和超晶格等信息。本文还系统介绍了高分辨X射线衍射中的倒易平面图的作法,以及相关的理论和实验方法,并据此获得了PbTiO3外延膜的应力状态、畴结构、相变等结构信息。     

In-situ neutron diffraction analysis on deformation behavior of duplex high Mn steel containing austenite and ?-martensite

The deformation behavior of Fe-17Mn-0.02C steel containing ?-martensite within austenite matrix has been investigated via in-situ neutron diffraction study at 298 K and 77 K. Based on the analyses of changes in phase fraction and lattice strain, it has been shown that the steel shows the deformation-induced phase transformation of austenite ?? ?-martensite ?? ????-martensite and the direct transformation of austenite ?? ????-martensite at both temperatures. However, the kinetics of such transformations vary with temperature, resulting in a higher and more persistent work hardening at 77 K than at 298 K.     

X-Ray Diffraction, Microstructure, and M?ssbauer Studies of Fe72Al28 Alloy Elaborated by Mechanical Milling

Nanocrystalline Fe₇₂Al₂₈ alloy samples were prepared by mechanical alloying process using planetary high-energy ball mill. The alloy formation and different physical properties were investigated as a function of milling time, t, (in the 0-24?h range) by means of X-ray diffraction technique, scanning electron microscopy (SEM), energy dispersive X-ray, and M?ssbauer spectroscopy. The complete formation of bcc-FeAl solid solution was observed after 4?h of milling. The lattice parameter quickly increased to a maximum value of 0.291?nm within the first hours of 12?h of milling, then decreased to a value of 0.2885?nm after 24?h. The grain size decreased from 55 to 10?nm, while the strain increased from 0.18 to 0.88%. Grain morphologies at different formation stages were observed by SEM. The M?ssbauer spectrum showed the presence of a singlet and sextet after 4?h of milling. The singlet indicated the presence of paramagnetic phase characteristic of A₂ disordered structure and the sextet with a mean hyperfine field, ??H _hf??, of 21?T was indicative of ordered DO₃ structure. After 8?h of milling, the paramagnetic phase disappeared allowing the appearance of a sextet. For the higher milling time, i.e., 24?h, the M?ssbauer spectrum was analyzed with two components. The first with ??H _hf?? equal to 29.9 T and the second with a ??H _hf?? value of 10.25 T.     

X-ray diffraction scattering by particles of a dispersed phase with a spatially ordered distribution in a crystal

X-ray diffraction scattering by precipitates (particles of a disperse phase) placed in the crystal in sites of a simple cubic lattice has been considered in the assumption that the precipitates have a cubic lattice of the same type as that of the matrix but differing from the matrix in that they have an ordered structure with a structure amplitude that is the same for all the particles. The scattering by such an ensemble of particles leads to the formation of satellite reflections which are located in the sites of a microlattice that is reciprocal to the macrolattice formed by the precipitates. The satellites are grouped in the vicinity of reciprocal-lattice (RL) points of the elastically deformed precipitate and have peaked intensity distributions that reflect the shape and dimensions of the crystal itself. One of the group of satellite sites of a given reflection from precipitates, which is taken to be reference, coincides with the point of the RL which corresponds to the average lattice parameter of a crystal with precipitates.     

退火对新型锆合金组织与性能的影响

采用扫描电镜(SEM)、电子背散射衍射(EBSD)、X射线衍射(XRD)、透射电镜(TEM)和万能试验机等,研究真空退火对新型Zr-Nb-O-Cu锆合金微观组织与力学性能的影响。结果表明:在580℃、3 h退火条件下,合金的平均晶粒尺寸为2.5μm,晶粒为等轴晶,退火前后均存在{0001}á1010?和{0001}á1120?两种织构,但基面织构强度有所降低。第二相颗粒在晶内和晶界呈弥散分布,为体心立方(BCC)结构的β-Nb相与密排六方(HCP)结构的Zr-Nb-Fe相,尺寸集中在30~150 nm之间。相对于原材,退火后合金沿轧制方向(RD)和垂直方向(TD)的屈服强度(σs)及抗拉强度(σb)均下降,试样均韧性断裂。3个方向的应变硬化指数(n)与塑性应变比(r)差异明显。晶粒与第二相的尺寸、织构等因素对力学性能有重要影响。     

Mechanical Properties of INCONEL 718 Parts Manufactured by Shaped Metal Deposition (SMD)

INCONEL 718 parts have been manufactured by shaped metal deposition (SMD), an additive layer manufacturing technique applying wire-based tungsten inert gas welding. This technique is aimed toward mass customization of parts, omitting time- and scrap-intensive, subtractive fabrication routes. SMD results in dense, ??near net-shaped?? parts without pores, cracks, or fissures. The microstructure of the SMD parts exhibit large, columnar grains with a fine dendritic microstructure. The interdendritic boundaries are decorated by small Laves phase precipitates and by MC carbides. Tensile tests were performed with different strain rates (10^?4, 10^?3, and 2?×?10^?3?1/s), but no dependency on strength or strain at failure was observed. The ultimate tensile strength was 828?±?8?MPa, the true plastic strain at failure 28?±?2%, the micro Vickers hardness 266?±?21 HV200, and the dynamically measured Young??s module was 154?±?1?GPa.     

Crystallization Behavior of Metallic GlassCo_（65．1）Fe_（4．7）Ni_（4．6）Si_（10．2）B_（15．4）

ＣｒｙｓｔａｌｌｉｚａｔｉｏｎＢｅｈａｖｉｏｒｏｆＭｅｔａｌｌｉｃＧｌａｓｓＣｏ＿（６５．１）Ｆｅ＿（４．７）Ｎｉ＿（４．６）Ｓｉ＿（１０．２）Ｂ＿（１５．４）ＬｉＺｏｎｇｑｕａｎ；ＱｉｎＹｏｎｇａｎｄＨｅＹｉｚｈｅｎ（李宗全），（秦勇）（何怡贞）（...     

三元合金沉淀过程动力学模型的研究

三元合金沉淀过程动力学模型基于微观相场扩散方程建立，以原子占位几率和序参数描述合金沉淀过程的成分簇聚和有序化。该模型将三维问题进行二维投影，在倒易空间求解。该模型无需预先设定新相结构和沉淀类型，可对实际三元合金的沉淀过程进行模拟研究。     

TEM study of superstructure in a perovskite lead lanthanum zirconate stannate titanate ceramic

The superstructure of an antiferroelectric Pb_0.97La_0.02(Zr_0.66Sn_0.25Ti_0.09)O₃ phase, whose composition is near the morphotropic-phase boundary, was characterized. Systematic selected-area diffraction revealed that there were two kinds of superlattice reflections in the pseudocubic reciprocal lattice, i.e. superlattice reflections (h, k, l all odd), and one-dimensional incommensurate superlattice reflections, where g denotes the vectors of fundamental or superlattice reflections. Convergent-beam electron diffraction disclosed that the average structure of the phase was rhombohedral with space group of . Based on the rhombohedral reciprocal lattice, the reflections were no longer superlattice but fundamental reflections, and the reciprocal vector of the one-dimensional incommensurate reflections was re-expressed as

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, where h, k, l are integers and (−h + k + l) = 3n. In the light of the average structure and the reflection condition, the superspace Bravais class of the phase with one-dimensional incommensurate structure was determined to be in a (3 + 1)-dimensional space. In addition, the origins of the superlattice reflections were also examined and discussed.     

What is a crystal to the new chemical crystallographer,after that first,automated structure analysis?

This educational review postulates the importance of maintaining an adequate level of crystallographic education among structure-dependent scientists whose interests are not primarily in crystallography, at a time when automation and validation have made it possible to obtain high-quality structure analyses in many cases with a minimum of crystallographic background. The topics addressed are intended to form a second round of crystallographic education for a novice user whose first round involved hands-on experience with structure solution and an introduction to elementary concepts. The specific topics, chosen for their relevance as basic knowledge and their lack of emphasis in many formal treatments, are (1) crystallographic reference frames and the utility of the reciprocal cell in geometrical calculations; (2) the relationship between the two concepts that constitute our model of the crystal, namely the unit cell and the lattice; (3) the manner in which an atom is represented in concept and in practice; (4) the importance of interleaved symmetry elements required by the presence of additional symmetry on a lattice; (5) the harnessing of the natural properties of the crystalline state for the potential manipulation of properties of synthetic crystals; and (6) useful terminology for navigating a crystal structure.     

Effect of lanthanum on the high-temperature strength of single crystals of highly refractory alloy VZhM4-VI containing rhenium and ruthenium

Metal Science and Heat Treatment - The effect of lanthanum on the high-temperature oxidation resistance of single crystals of alloy VZhM4-VI used for casting single-crystal blades of gas turbine...     

Phase and structural transformations in Ti-Ta alloys

A systematic study of structural and phase transformations in Ti-Ta quenched alloys in a wide concentration range has been carried out. Boundaries of the concentration ranges of the hexagonal α′ and orthorhombic α″ phases have been determined. Morphological forms of the transformation products have been studied. Distribution of diffuse scattering in the space of the reciprocal lattice of the β phase and its dependence on the Ta concentration have been analyzed.     

A study of the relationship between the phase transitions and transport properties in Zn0.81[Pt(C2O4)2]·6H2O

An investigation into the variation of the intensity of the satellite reflections with temperature in Zn_0.81[Pt(C₂O₄)₂]·6H₂O is reported. The first appearance of satellites corresponds to a big fall in conductivity and a large change in the thermopower, even though the intensity of the satellites is quite weak. The phase transition from Cccm to Pccn space group results in the appearance of new satellites and further large changes in both conductivity and thermopower.     

Comparison of calculations for interplanar distances in a crystal lattice

The derivations for the general formulae of lattice interplanar distances are reviewed along with the methods using elementary geometry, intermediate Cartesian axes, and reciprocal lattice vectors. To highlight the characteristics of these three methods and the connections between them, examples for the simple cases such as orthorhombic, hexagonal, and rhombohedral systems are included. Calculations from reciprocal space are established from those from direct space with heavily involved mathematics for which details are seldom included in crystallography monographs. The only geometric method found in the literature for the interplanar distances in a crystal lattice is derived for a few specific simple cases with cos²α?+?cos²β?+?cos²γ?=?1, where α, β, and γ are the angles between the normal to the plane and the axes of a orthogonal system. However, the geometric method introduced in this work is a newly developed method and this method is complementary to other methods including the advanced contemporary reciprocal method. The connections between Cartesian and crystal coordinate systems, for angular relationships and the volume of unit cell are revealed. The interplanar spacing in non-primitive lattice and crystals are also discussed.     

Experimental Determination of Phase Equilibria in the Co-Cr-V Ternary System

The phase equilibria in the Co-Cr-V ternary system were investigated by means of optical microscopy, electron probe microanalysis and x-ray diffraction. Four isothermal sections of the Co-Cr-V ternary system at 800, 1000, 1100 and 1200?°C were established. The experimental results show that: (1) no ternary compound was found in this system; (2) the ?? and (V, Cr) phases form the continuous solid solutions from the Co-Cr side to Co-V side in the isothermal sections at 800-1200?°C.