Pd替代对Ti-Zr-Ni准晶合金中的相形成与稳定性影响（英文）EI北大核心CSCD

Pd能用来作为添加元素改善Ti-Zr-Ni准晶合金的吸氢性能,但是Pd添加的作用机制仍然不清楚。本工作通过采用XRD、TEM、DSC分析技术研究了Pd在Ti45Zr38Ni17和Ti40Zr40Ni20两个合金中对Ti、Zr的替代行为。结果显示：在前1个合金中,替代4%-6%（原子分数,下同）Ti或4%Zr能够确保纯二十面体准晶形成;在后一个合金中,替代3%-4%Ti或3%以下Zr才能形成纯二十面体准晶。这说明Ti具有更高的替代极限。Ti39Zr38Ni17Pd6与Ti36Zr40Ni20Pd4两个衍生准晶合金在400℃温度下退火会转变为晶体相,而它们的初始准晶合金Ti45Zr38Ni17和Ti40Zr40Ni20在400℃仍然结构稳定,这反映出添加Pd后准晶合金的热力学稳定性变低。这种替代趋势和准晶稳定性的降低很可能归功于Pd具有适宜的原子尺寸。     

铸态Ti-Zr-(Ni,Co)伪三元准晶合金研究

沿Ti9(Ni，Co)4-Zr变电子浓度线设计系列合金成分．用吸铸方法可制备出Ti-Zr-(Ni，Co)准晶，其中Ti42Zr40(Ni，Co)18为形成准晶的最佳成分点，Ti-Zr-(Ni，Co)伪三元准晶系列的准点阵常数介于0．506～0．518nm之间。实验结果表明，Co是形成准晶的不利组元，其含量的增加将促使Ti2Ni、fcc-Zr2Ni和β-Zr(Ti)固溶相的形成，使合金中准晶相的含量大为降低；但适量Si的加入(～2at％)能促进Ti-Zr-(Ni，Co)准晶的形成。     

Pd替代对Ti-Zr-Ni准晶合金结构的影响

针对Ti_(45)Zr_(38)Ni_(17)与Ti_(40)Zr_(40)Ni_(20)准晶合金用X射线衍射仪、透射电子显微镜与金相等手段研究了不同含量的Pd替代对其结构的影响.在吸铸态下,前一个合金形成了二十面体准晶相(IQC)与少量配位数为8的bccβ-(Ti,Zr)相,用2%Pd(原子分数,下同)对合金的Ti或Zr组元替代,抑制了β-(Ti,Zr)相析出并促使配位数为14的MgZn_2结构的简单六方C14 Laves相生成.而后一个合金中IQC相则与少量简单六方α-(Ti,Zr)共存,在2%Pd替代后α-(Ti,Zr)消失,生成了单一的IQC相,但当Pd替代量增加到6.7%或13.3%时,配位数为12的IQC相急剧减少而C14相大量析出,并在Ti_(40)Zr_(26.7)Ni_(20)Pd_(13.3)合金中生成了单一C14相.结果表明,添加中等尺寸的Pd原子有利于提高Ti-Zr-Ni合金的原子密堆性,使合金趋于生成高配位数的Laves相,这种相的Fermi面与Brillouin区的相互作用不显著,偏离了电子相的稳定机制.     

Ti40Zr40Ni20块体铸态准晶的相变研究

用吸铸法制备出单相块体Ti40Zr40Ni20。其准点阵参数为aR=0．523nm。通过差示扫描量热法(DSC)和X射线衍射等手段研究了该铸态准晶合金在加热过程中的相变行为。结果表明,Ti40Zr40Ni20铸态准晶在964K温度以下稳定;在964K附近温度,准晶发生分解,形成由β-Zr(Ti)固溶体与C14相组成的两相混合组织;在1107K,该混合物发生熔化。     

吸铸Ti-Zr-Ni准晶棒的成分偏析

探讨了铸态Ti—Zr-Ni准晶的成分偏析问题。通过水冷铜模吸铸法制备6个名义成分为Ti40Zr40Ni20的Ф3mm圆柱状样品，采用X射线衍射与能谱分析分别对样品底端和顶端的相结构与成分分布进行了测定。结果表明，这些样品在一定长度范围内都形成了近单一的二十面体准晶相，最长的准晶样品达到40mm。它们都存在明显的宏观成分偏析，其中Ni易于在样品的底端富集，而Ti在顶端富集，这属于比重偏析；而Zr的偏析与工艺控制有关，可通过改善工艺消除它。     

Ti-Zr-Ni系三元准晶的成分特征研究

系统研究了两个等电子浓度线(e／a=1．20,1．25)上Ti-Zr-Ni铸态合金的组织与结构,发现吸铸法可在很宽的成分区间(TixZr100-x)100-yNiy,43．75％≤x≤81．25％,17％≤y≤20％)内获得Ti-Zr-Ni准晶,其中,Ti40Zr40Ni20为理想准晶成分,能形成长15mm、直径6mm的单相准晶棒．准晶成分特征研究表明：Ti-Zr-Ni准晶系也具有与Al基三元准晶系相似的相图特征．一方面,Ti-Zr-Ni准晶与其类似相一起构成准晶“等电子浓度线”现象;同时,三元准晶成分满足准晶“变电子浓度线”特征,形成准晶的理想成分TiaoZraoNi20位于准晶等电子浓度线与变电子浓度线交点处．     

铸态Ti-Zr-Ni准晶基合金的室温力学性能

用吸铸法制备出含Ti(Zr)固溶体韧性相的Ti-Zr-Ni准晶合金棒，通过维氏显微硬度测定和单向压缩实验等方法研究了该新型合金的室温力学性能和断裂行为。结果表明：Ti-zr-Ni准晶基复相(α-Ti(Zr) I)合金力学性能良好，维氏显微硬度值接近5.5GPa，断裂强度达到1000MPa，Young’s模量值23-36GPa。其中，Ti60Zr25Ni15合金的室温弹性应变可达4．2％，是Al基准晶合金的4倍。但其室温单向压缩时的断裂方式仍为准解理断裂，属脆性断裂。     

Ti-Zr-Ni-Cu非晶系的等电子浓度特征

以准晶成分Ti40Zr40Ni20为基准,在Ti—Zr-Ni-Cu系中设计出电子浓度为1.200和原子尺寸为0．1474nm的系列合金,并用铜模吸铸法制备直径为3mm的合金棒试样．结果表明,Ti12Zr55Ni13Cu20成分附近可形成块体非晶合金,而Ti3Zr60Ni12Cu25和Zr60Ni10Cu30成分点上形成了单一的四方Zr2Cu型非晶相关相．准晶、块体非晶合金和Zr2Cu相是具有相同电子浓度的电子化合物,它们在成分图上表现出鲜明的等电子浓度特征,表明块体非晶合金的等电子浓度判据适用于Ti-Zr-Ni-Cu非晶系．二十面体与截角八面体间的结构关联可作为准晶或非晶合金多型性转变成Zr2Cu相的结构模型．     

Pd替代对Ti-Zr-Ni准晶合金中的相形成与稳定性影响（英文）

Pd能用来作为添加元素改善Ti-Zr-Ni准晶合金的吸氢性能,但是Pd添加的作用机制仍然不清楚。本工作通过采用XRD、TEM、DSC分析技术研究了Pd在Ti45Zr38Ni17和Ti40Zr40Ni20两个合金中对Ti、Zr的替代行为。结果显示:在前1个合金中,替代4%~6%(原子分数,下同)Ti或4%Zr能够确保纯二十面体准晶形成;在后一个合金中,替代3%~4%Ti或3%以下Zr才能形成纯二十面体准晶。这说明Ti具有更高的替代极限。Ti39Zr38Ni17Pd6与Ti36Zr40Ni20Pd4两个衍生准晶合金在400℃温度下退火会转变为晶体相,而它们的初始准晶合金Ti45Zr38Ni17和Ti40Zr40Ni20在400℃仍然结构稳定,这反映出添加Pd后准晶合金的热力学稳定性变低。这种替代趋势和准晶稳定性的降低很可能归功于Pd具有适宜的原子尺寸。     

Laves相Ti36Zr40Ni20Pd4合金的吸氘行为

针对Ti36Zr40Ni20Pd4合金用X射线衍射仪和气固反应系统研究了其吸铸之前的晶体结构与吸氘特性。结果表明,吸铸前Ti36Zr40Ni20Pd4合金母锭形成了配位数为14的MgZn2结构的简单六方C14Laves相,晶格常数a=0.5287nm与c=0.8610nm。简单活化后,该合金可在室温下大量吸氘,浓度达到10.96mmol·D2/g·M(D2指氘分子,M指合金)。经过一次吸放氘循环后,吸氘动力学显著提高,吸氘速率常数达到0.015s-1。相对于成分相同的准晶相,Laves相Ti36Zr40Ni20Pd4合金吸氘较慢,但吸氘量相近,具有一定的储氢前景。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.