Microstructure Transformation and Refinement Mechanism of Undercooled Cu-Ni-Co Alloy Based on Simulation of Critical Cutting Speed in Ultrasonic Machining

Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(ΔT)was systematically studied.It is found that the two alloys experience the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,but the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscopy(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it could be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.On this basis,in the processing of copper base alloys,there will be serious work hardening phenomenon and machining hard problem of consciousness problems caused by excessive cutting force.A twodimensional orthogonal turning finite element model was established using ABAQUS software to analyze the changes in cutting speed and tool trajectory in copper based alloy ultrasonic elliptical vibration turning.The results show that in copper based alloy ultrasonic elliptical vibration turning,cutting process parameters have a significant impact on cutting force.Choosing reasonable process parameters can effectively reduce cutting force and improve machining quality.

Effect of Co on Microstructure Transformation and Refinement Mechanism of Undercooled Cu-Ni Alloy

Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(DT)was systematically studied.It was found that the two alloys experienced the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The experimental results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,whereas,the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscope(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it can be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.

Phase and Structure in the System Gd_(2-x)Eu_xZr_2O_7 (0.0≤x≤2.0)

Pyrochlore Gd2Zr2O7 are considered as an excellent candidate for treatment of radioactive waste forms, because of its superior physical, chemical and anti-irradiation properties. To investigate the phase and structure of pyrochlore Gd2Zr2O7 used for immobilizing Pu （Ⅲ）, trivalent europium was used as the simulacrum for plutonium with trivalence. The compounds of stoichiometry Gd2-xEuxZr2O7（0.0≤x≤ 2.0） synthesized by high temperature solid state reaction method, were analyzed with the help of XRD and Rietveld structural refinement method. The results indicated that the phases of compounds continuously kept the phase of pyrochlore under our experimental condition. The linear relation between a and x was discovered in the system of Gd2-xEuxZr2O7（0.0≤x≤ 2.0） at 1 773 K, which accorded with a = 10.538 41 ＋ 0.008 95 x, V = 1 170.373 32 ＋ 2.985 97 x.

Discovery of Stolzite in China and Refinement of Its Crystal Structure

Although stolzite was discovered in Yaogangxian, Hunan Province, China, in 1948, no formal report about this mineral has been published. Recently its crystal structure has been refined by means of the Rietveld method. The cell dimensions of the mineral are: a=b= 0.544503(3) nm, c= 1.20495(1)nm and α=β=γ=90° . The X, Y and Z coordinates of the atom O refined by the authors are 0.2637, 0.1137 and 0.0706, respectively. The length of the W-O bond is 0.17826 nm and the angle of the O-W-O bound are 123° and 103° ,respectively.

Xray Diffraction Data and Rietveld Structure Refinement for CeNi_5Sn

The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constants a =0 48912(3) nm, c =1 973(2) nm and D x=8 974 g·cm -3 . The Rietveld structural refinement was performed, leading to R p=0 138 and R wp =0 185. The figure of merit F N for the XRD data is F 30 =82 1(0 0068, 54). The X ray powder diffraction data are presented.

X-RAY RIETVELD STRUCTURE REFINEMENT OF ErNiSb

The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and reliability factors were refined to be a=6.268 3(1), V=246.29^(3), Z=4, D_(x)=9.377 g/cm^3, R_(B)=3.57%, R_(F)=3.64%, R_(p)=6.63%, R_(WP)=8.80%.

Influence of Oxygen Addition on Structure and Properties of Titanium Produced by Electroslag Remelting

The current work is devoted to the investigation of oxygen impact on the structure and properties of titanium. For this purpose, oxygen was introduced into titanium during chamber electro-slag remelting by three different methods: alloying by oxygen-rich residues from the Kroll process to final values between 0.053 wt.-% and 0.40 wt.-%, by reaction with the gas phase to 0.27 wt.-% and by introduction of TiO2 nanoparticles to 0.73 wt.-%. The influence of oxygen on microstructure of titanium during crystallization, heat treatment and deformation is determined as well as the effect of oxygen on the hardness and the mechanical properties of the material in different structural states. Furthermore, control methods of the structure formation process by thermal effects are proposed. Results show that the chamber electroslag remelting allows obtaining a homogeneous structure of the ingot in the investigated range of oxygen content in titanium. The hardness does not vary by more than 10 percent in longitudinal or radial direction in any of the remelted ingots.

Phase and Rietveld Refinement of Pyrochlore Gd_2Zr_2O_7 Used for Immobilization of Pu(Ⅳ)

The phase of pyrochlore Gd_2Zr_2O_7 used for immobilization of Pu （Ⅳ） was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd_2Zr_2-_xCe_xO_7 （0.0≤x≤2.0） were synthesized via a high temperature solid reaction method with Gd_2O_3 and ZrO_2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 ＋ 0.00825 x （0.2≤x≤2.0）, while V= 0.14668 ＋ 0.00711 x （0.2≤x≤2.0） was also achieved.

Hydrothermal Synthesis and Thermal Stability of Natural Mineral Lindgrenite

A natural mineral, lindgrenite Cu3 （ MoO4 ）2 （ OH）2, was synthesized from a mixture of sodium molybdate, copper sulfate, and morpholine in water under autogenous pressure at 170 ℃. The crystal structure of the mineral was determined and the final refinement for 791 observed reflections with Ⅰ 〉 2σ（Ⅰ） gave R1 = 0. 0205 and wR2 = 0. 0496. The thermal stability of the mineral was investigated by using TG-DTA and variable-temperature in situ X-ray diffraction（XRD） techniques. The crystalline Cu3Mo2O9 was obtained when the mineral underwent thermal dehydration at a temperature ranging from 300 to 400 ℃, and the mixture of MoO3 and CuO was formed through decomposition of Cu3Mo2O9 at a temperature ranging from 650 to 700 ℃. Therefore, the structure of the mineral was thermally unstable at above 300 ℃, suggesting that Lindgrenite was likely formed via the hydrothermal route occurring in the nature.

X-ray Powder Diffraction Data and Rietveld Refinement for NdCoGe_3

オ-ray powder diffraction data and crystal structure of RE compound NdCoGe3 were studied by using X-ray powder diffraction and refined by the Rietveld profile fitting method. The compound has the tetragonal BaNiSn3type structure, space group I4mm (No.107) a=0.42961(2) nm, c=098147(4) nm, V=0.018114 nm3, Z=2 and Dx=7.717 g·cm-3. The figure of merit FN for the powder data is F30=623 (0.0107, 45). Structure refinement was performed with 110 reflections and led to Rp=11.78% and Rwp=16.56%.

Structural and Chemical Characteristic of Tourmaline, and Mineralogy of Associated Micas from Tourmaline Bearing Quartzite of KombéII (Bafia Group, Central Africa Fold Belt);Implication on the Metamorphic Conditions

Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had been recognized among accessory minerals. In the present study, attention is focus on the tourmaline bearing quartzite to the southeast of Kombé II. Structure refinement shows that tourmaline is a Fe-dravite with the formula X(Na0.95[]0.05)Y(Mg2.39Fe0.61)Z(Al5.10Mg0.90)(BO3)3T[Si6O18](OH)3[(O,OH)0.88F0.12]. The Fe-dravite is hosted in a Ca-poor quartzite, which is made up, in addition to quartz and tourmaline, of biotite and muscovite. The structure of the dravites shows a low vacancy at the X site, which militates for a crystallization of the tourmaline at a high temperature > 750℃. This is in agreement with previous work which shows that the metamorphic peak in the associated biotite gneiss reaches 825℃. The R1 value of 1.24% means that the crystal structure of the tourmalines is of high quality. The genetical link between gold mineralization and tourmaline should stimulate exploration interest in the study area.

The three-dimensional structure of trichosanthin refined at 2.7resolution

The three-dimensional structure of trichosanthin crystallizing in space group C2 has been refined at 2.7 resolution from a previously reported starting model at 3 resolution based on a solvent flattened map and the revised primary structure consisting of 247 amlno-acids.The final R-factor is 19.2% with the root mean-square deviations of 0.018 from ideal bond lengths and of 2.2° from ideal bond angles.Trichosanthin molecule is composed of two domains,the large domain consisting of 181 amino-acld residues starting from N-terminus and the small domain con- sisting of the rest of the amino-acid residues.The molecule contains eight α-helices,five β-sheets made of sixteen β-strands,and some reverse turns.It is noteworthy that some of the α-helices and β-sheets show irregular hydrogen bonding patterns.Six of the thirteen residues absolutely conserved in eleven ribosome-inactivating proteins are located in a cleft near the interface of the two domains and they are likely to be active sites.Three additional conservative residues located in the cleft region might make some functional contribution as well.

Role of polarization evolution in the hysteresis effect of Pb-based antiferroelecrtics

The electric field-induced irreversible domain wall motion results in a ferroelectric(FE) hysteresis. In antiferroelectrics(AFEs), the irreversible phase transition is the main reason for the hysteresis effects, which plays an important role in energy storage performance. Compared to the well-demonstrated FE hysteresis,the structural mechanism of the hysteresis in AFE is not well understood. In this work, the underlying correlation between structure and the hysteresis effect is unveiled in Pb(Zr,Sn,Ti)O_(3) AFE system by using in-situ electrical biasing synchrotron X-ray diffraction. It is found that the AFE with a canting dipole configuration, which shows a continuous polarization rotation under the electric field, tends to have a small hysteresis effect. It presents a negligible phase transition, a small axis ratio, and electric field-induced lattice changing, small domain switching. All these features together lead to a slim hysteresis loop and a high energy storage efficiency. These results offer a deep insight into the structure-hysteresis relationship of AFEs and are helpful for the design of energy storage material.

An in-depth multi-technique characterization of rare earth carbonates-RE_(2)(CO_(3))_(3)·2H_(2)O-owning tengerite-type structure

The present study has been conducted to contribute,once and for all,filling the lack of structural information for the whole class of rare earth(RE)carbonates owning the tengerite-(Y)structure.A complete structural characterization,carried out by Rietveld refinement of X-ray powder diffraction(XRD)data,was comparatively performed for the first time on several hydrated RE carbonates,having the general chemical formula RE_(2)(CO_(3))_(3)·χH_(2)O,RE=Y,Gd,Tb,Dy,Ho and Er.All samples share the same space group and lattice parameters similar to tengerite-(Y);the structures are also closely related,consisting in all cases of a three-dimensional framework of nine-fold coordinated RE atom polyhedral,linked together by carbonate ions.In addition to relatively minor changes in fractional coordinates of atom sites and corresponding interatomic distances,the only perceivable difference lies in the lattice parameters affected by the ionic radius of RE^(3+).However,in the case of Er,which has the lowest cationic radius among the analyzed RE,the stabilization of tengerite structure is at its limit condition,because the carbonate groups are heavily distorted.Furthermore,FT-IR and Raman spectra confirm the main structural features obtained by Rietveld refinements.The observed morphology of the various samples is almost the same,being characterized by the presence of bidimensional rod-like particles grouped in agglomerates,typical of tengerite crystals,thus indicating that the crystallization mechanism occurring during the hydrothermal synthesis is the same,irrespective of the involved RE cation.

Interface conjunction factors of the second phase particles in alloys and their effects

The second phase in multi-phase alloys has connection with many important phenomena such as aging strengthening,dispersion strengthening,secondary hardening,crystal refinement.In this paper,the interface conjunction factors of the interface between MC(M=V,Nb,Ti) and austenite and martensite are calculate out.The relationship between these factors and the characteristics are analyzed.The reason for the second phases being fine and dispersing and their strengthening and toughening effect on the alloy is explained using the relationship.Based on the relationship,the valence electron structure of the interface between the second phase particles and the matrix can be optimized by changing the alloying elements,which make it possible to design the composition of alloys from the valence electron structure of the second phase particles.

Ti-Pt合金金属间化合物的脆韧转变研究

相变是调控材料性能的一种重要方式. Ti–Pt合金作为一种重要的高温相变材料,受到了广泛的关注.但是,金属间化合物的固有脆性和其晶体低对称性、相成分复杂等因素极大限制了材料的应用.本文选取主要包含Ti3Pt和αTiPt两相组织的Ti-35 at%Pt(Ti-35Pt)合金作为研究对象,通过扫描透射电子显微镜下的表征和原位加热实验、扫描电子显微镜下的微米柱原位压缩实验等方式研究发现了Ti-35Pt合金中的脆韧转变现象.当材料加热至一定温度后,αTiPt相可以从Ti3Pt相中析出,并产生孪晶结构,极大细化相结构,细化后的结构具有明显改善的塑性变形和加工硬化能力.后续的透射电子显微镜表征发现,相变和位错滑移是材料主要的塑性变形机制,该现象在低对称性的金属间化合物中十分罕见.实验结果证明金属间化合物可以通过相变调控材料相结构来获取塑性变形能力,实现材料脆韧转变.