贵金属与铝二元合金的形成热

运用Ｍｉｅｄｅｍａ理论计算ＣｕＡｌ、ＡｇＡｌ、ＡｕＡｌ构成的三个二元系统的整个成分范围的液态混合焓,计算的结果同已有的实验测量结果比较表明,计算值同实验结果符合得比较好。同时,也计算了以上三个二元系统的整个成分范围的固态合金形成焓,并将计算结果同已有的实验结果进行了比较。结果表明,对ＣｕＡｌ、ＡｇＡｌ二系统,符合得比较好,而对ＡｇＡｌ系统,计算值与实验值有较大的差别,但总的趋势是正确的,这证明了Ｍｉｅｄｅｍａ理论计算得到的贵金属与铝二元合金系统的混合焓和形成焓是合理的。同时讨论了原子尺寸因素、电负性、电子轨道能量等对合金形成焓的影响。     

蒸发法制备Ni－Ti纳米非晶合金粒子

采用气相蒸发法制备纳米量级的Ｎｉ－Ｔｉ非晶合金粒子，研究了各种因素对Ｎｉ－Ｔｉ纳米非晶合金粒子形成的影响，并用透射电子显微镜，高分辨电子显微镜，Ｘ射线衍射仪和能谱等多种手段对纳米非晶合金粒子进行了表征．结果表明，当粒子成分在共晶区Ｎｉ（４０）Ｔｉ（６０）附近时，容易形成非晶；较低惰性气体压力和较高蒸发温度有利于Ｎｉ－Ｔｉ纳米非晶粒子的形成．     

纳米晶Co_(78)Ni_(22)合金热稳定性

采用DSC、XRD和TEM等手段研究了喷射电沉积制备的5.1 nm纳米晶Co78Ni22合金的热稳定性,并对其热力学参数进行了分析与计算。结果表明,该纳米Co-Ni合金具有良好的热稳定性,以10℃/min加热时的DSC放热峰值对应温度为389.9℃,放热焓为14.26 J·g-1,晶粒长大激活能为269.1 kJ·mol-1。在加热过程中,温度为340℃时,合金晶粒尺寸急剧长大,同时ε相向α相转变,相变的结束温度约为370℃,高温形成的α相在随后冷却中不发生转变。DSC测定的晶粒长大为相变结束后的α相晶粒长大,其激活能与自扩散激活能相近,因此晶粒长大由晶内扩散控制。     

二元过渡族金属合金非晶态形成规律

依据机械合金化引起固态反应非晶化（ＳＳＡＲ）机制,选择等原子成分合金的形成焓ΔＨｆ和自扩散激活能差ΔＨｓ为参数坐标构成的坐标系。揭示了机械合金化引进二元过渡族合金合金非晶化的规律。基于已有的实验事实,确定二元过渡族金属合金在机械合金化时形成非晶的条件为Δｆ〈－０．００５７５０（ΔＨｓ）＾２＋１．３４５６３６（ΔＨｓ）－５８．７４４０９５据对已有实验结果的５８个过渡族金属二元合金系统的研究表明,对其     

pH值和煅烧温度对Cu-Ni纳米合金的合成和特性的影响（英文）

用柠檬酸-凝胶法合成的前驱体制备Cu-Ni纳米合金。研究溶液初始pH值和煅烧温度对Cu-Ni纳米颗粒的成分、晶粒结构、纯度、形貌、均匀性和晶粒尺寸的影响。这两种参数对合成的纳米颗粒的晶粒结构、成分和晶粒尺寸都有很大的影响。溶液初始pH值为1时制备的Cu-Ni纳米合金不含杂质,在300、400和500℃煅烧分别得到Cu_(0.42)Ni_(0.58)、Cu_(0.45)Ni_(0.55)和Cu_(0.52)Ni_(0.48)。溶液初始pH值为1.6和3时,所得Cu-Ni纳米合金的晶粒尺寸随着煅烧温度的升高而增大。pH值为3时所得Cu-Ni纳米合金的Ni含量随着煅烧温度的升高而逐渐增加。     

Al-Cu-RE三元合金热力学性质的Miedema理论计算

合金形成焓是确定合金的稳定性及其非晶形成能力的重要因素。采用Miedema理论和几何外推模型相结合,预测了Al-Cu-RE(RE=La~Lu)体系液态合金整个成分范围的混合焓。计算结果表明:Al-Cu-RE三元体系的混合焓比Al-Cu二元合金的混合焓更负,稀土元素与Al、Cu之间的化学势差对混合焓的贡献起主要作用。当铝与稀土元素含量相同时,随着铜含量的减少,合金混合焓越来越负,从而表明在Al-Cu合金中加入稀土元素有利于Al-Cu-RE三元合金的形成。同时较负的混合焓是合金体系易于非晶化的重要条件之一,也说明Al-Cu-RE三元体系非晶形成能力较强。计算了Al8Cu4RE和Al Cu RE等三元化合物的形成焓,计算得到的Al Cu RE的形成焓比相应的Al8Cu4RE的形成焓要负,说明Al Cu RE更稳定;同时计算了金属间化合物Al(Cu1-xREx)3、Al(Cu1-xREx)、Al2(Cu1-xREx)的形成焓随稀土含量变化趋势。计算结果为Al-Cu-RE体系非晶形成的成分设计和相关性能研究提供了重要的热力学数据。     

碱金属二元合金的形成焓

根据合金组元原子半径不同引起的弹性畸变，运用Ｍｉｅｄｅｍａ理论系统地研究了碱金属元素为基元的二元金金属间化合物和无序合金形成焓。计算结果表明，得到的形成焓同已有的由第一原理赝势处理方法得到的结果符合得很好。     

Ta-TM(TM=Ti,Cr,Co,Ni)二元合金形成焓的亚规则模型

形成焓是描述合金形成能力和稳定性的重要参数.用亚规则模型对Ta-TM(TM=Ti,Cr,Co,Ni)二元合金的形成焓进行理论计算.目的是了解这四种Ta合金的热力学性质,预测其中间相的存在.结果显示亚规则模型对所研究的二元合金的形成焓结果能准确地描述和解释已有实验结果.这为制备和开发广泛应用于化学工业的耐腐蚀、航空航天工业的高温结构Ta合金材料提供了理论支撑.     

溅射Ni16Co26Cr10Al纳米晶涂层的1000℃抗氧化性能

利用磁控溅射技术在铸造Ni16Co26Cr10Al合金上溅射了相同成分的纳米晶涂层.1000℃氧化试验结果表明由于溅射Ni16Co26Cr10Al纳米晶涂层晶粒尺寸细小,促进了保护性氧化物形成元素Al向氧化前沿的快速扩散和保护性Al2O3层的快速形成,使得溅射Ni16Co26Cr10Al纳米晶涂层表现出比M38合金更优异的抗氧化性能.     

Zr-4合金表面变形纳米结构TEM研究

利用透射电镜对Zr-4合金表面进行高能喷丸处理所致纳米结构的微观组织演变特征进行了研究.结果表明,经过喷丸处理变形后,Zr-4合金表面形成一层平均晶粒尺寸为几纳米至十几纳米的致密纳米层,随着离表面距离的增加,晶粒尺寸也不断增加.通过对Zr-4合金的变形行为以及微观结构组织演变的观察和分析,探讨了纳米晶的形成机制.     

Microstructure and mechanical properties of duplex tiAl alloys containing Mn

A study has been made of the effect of Mn on the structure and compressive mechanical properties of duplex TiAl alloys. In order to clarify the separate effect of Mn and Al contents, the effect of Ti/Al ratio was also studied by analyzing the behavior of alloys with different Ti/Al ratios at the fixed Mn content. Addition of 3 at.% Mn to the binary Ti₅₃Al₄₇ alloy decreases the tetragonality and the unit cell volume of γ structure. It also promotes the formation of twin-related structure, the refinement of interlamellar spacing and grain size, and the increase in the volume fraction of lamellar grains. Increase in Ti/Al ratio at the fixed Mn content results in the further decrease in the tetragonality and unit cell volume and the refinement of grain size, while it decreases the volume fraction of lamellar grains. The modification of microstructure directly influences the compressive properties and deformation mode of duplex TiAl alloys. It has been found that Mn addition and increase in Ti/Al ratio enhance the plasticity of duplex alloys. Generation of mobile dislocations at the twin intersections has been found to occur in Mn containing alloys. Such dislocation generation at the twin intersections as well as the promotion of deformation twins in Mn containing alloys are all beneficial for improving the ductility of duplex TiAl alloys.     

Effect of grain size reduction on high temperature oxidation of binary two-phase alloys

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铸造Al-Si合金熔体处理——晶粒细化

对亚共晶Ａｌ－Ｓｉ铸造合金进行细化处理已成为一种基本操作。中间合金（Ａｌ－Ｔｉ,Ａｌ－Ｔｉ－Ｂ和Ａｌ－Ｂ合金）在亚共晶Ａｌ－Ｓｉ铸造合金中与在工业纯铝和变形铝合金中的晶粒细化行为存在较大的差异。Ａｌ－３Ｔｉ－３Ｂ,Ａｌ－３Ｂ中间合金在Ａｌ－Ｓｉ铸造合金中表现出优异的晶粒细化效应,Ｓｉ与晶粒细化剂的交互作用在其中扮演着重要的角色。通过炉前对熔体进行快速热分析可以对晶粒细化效果和变质程度进行评价和预测,继而控制熔体处理的质量。对于亚共晶Ａｌ－Ｓｉ铸造合金,归纳起来有四种晶粒细化机理：包晶反应理论、共晶反应理论、硼化物颗粒理论和超形核理论。仅对Ａｌ－Ｓｉ铸造合金细化处理的最新进展、Ｓｉ与晶粒细化剂的交互作用和晶粒细化机理进行综合评述     

The Effect of Small Amount of Titanium Addition on the Grain Refinement and Mechanical Properties of ZA48 Alloy

Low-titanium (Ti) aluminum alloys were prepared, and the effects of Ti elements on the microstructure, tensile property, and wear property of zinc-aluminum alloys were investigated. The addition of Ti is found to be effective in refining the grain size of the zinc-aluminum alloys. With a Ti content of 0.04 wt.%, the minimum grain size is achieved, and the tensile property of the test alloy reaches the maximum. Wear resistance is improved with decreased grain size. The grain-refining mechanism of the low-Ti aluminum alloys can be explained by the formation of Al₆₆Ti₂₅Zn₉ particles. These particles serve as the nucleation sites and effectively restrict α phase growth.     

Ti对Zr-Nb二元合金β结构稳定性和力学性能的影响

利用团簇成分式方法设计了[Zr-Zr₁₄](Zr,Nb)3系列二元合金,进而采用Ti替代部分Zr形成三元合金;采用真空铜模吸铸快冷技术制备合金棒材,利用XRD、OM、TEM等对其进行微观组织表征和力学性能测试。结果表明,随着Nb含量增加,Zr-Nb二元合金基体结构从hcp-α向bcc-β转变,β结构稳定的同时伴随有ω相析出。适量Ti添加可显著抑制ω相的析出,进一步改善了合金的β结构稳定性。其中,单相bcc-β合金[Ti-Zr₁₄]Nb3(Zr-17.37Nb-2.98Ti,质量分数,%)表现出低弹性模量(E=57 GPa)的同时具有最佳的力学性能(屈服强度σYS=557 MPa、延伸率δ=15.5%)。     

A novel Al–Ti–B alloy for grain refining Al–Si foundry alloys

Al–Ti–B refiners with excess-Ti (Ti:B > 2.2) perform adequately for wrought aluminium alloys but they are not as efficient in the case of foundry alloys. Silicon, which is abundant in the latter, forms silicides with Ti and severely impairs the potency of TiB₂ and Al₃Ti particles. Hence, Al–Ti–B alloys with excess-B (Ti:B < 2.2) and binary Al–B alloys are favored to grain refine hypoeutectic Al–Si alloys. These grain refiners rely on the insoluble (Al,Ti)B₂ or AlB₂ particles for grain refinement, and thus do not enjoy the growth restriction provided by solute Ti. It would be very attractive to produce excess-B Al–Ti–B alloys which additionally contain Al₃Ti particles to maximize their grain refining efficiency for aluminium foundry alloys. A powder metallurgy process was employed to produce an experimental Al–3Ti–3B grain refiner which contains both the insoluble AlB₂ and the soluble Al₃Ti particles. Inoculation of a hypoeutectic Al–Si foundry alloy with this grain refiner has produced a fine equiaxed grain structure across the entire section of the test sample which was more or less retained for holding times up to 15 min.     

Modified embedded-atom method interatomic potentials for the Ti–C and Ti–N binary systems

Modified embedded-atom method (MEAM) interatomic potentials for the Ti–C and Ti–N binary systems have been developed using previously developed MEAM potentials of Ti, C and N. The potential parameters were determined by fitting to experimental data on the enthalpy of formation, lattice parameter, elastic constants, thermal linear expansion of NaCl-type TiC and TiN, and dilute heat of solution of carbon and nitrogen atoms in hexagonal close-packed Ti. The potentials can describe fundamental physical properties (structural, elastic, thermal and surface properties) of the alloys well, in good agreement with experimental information or first-principles calculations. The applicability of the potentials to atomistic investigations of interactions between TiC or TiN precipitates and matrix, dislocations or other defects, and their effects on deformation and mechanical behaviors of metallic alloys is discussed.     

Vacuum sintering and solution plus aging heat treatment of β eutectoid bearing binary Ti alloy

Binary Ti alloys bearing β eutectoid stabilisers (i.e. Cu and Mn) were produced by powder blending followed by cold pressing and vacuum sintering as this is identified as an alternative cost-effective manufacturing method to lower the cost of Ti alloys. The sintered Ti-Cu and Ti-Mn alloys were subsequently heat treated via a solution treatment in the β field plus aging. The aim is to investigate a cheap and efficient method to change and tailor the mechanical behaviour via microstructural control. Heat treating the binary Ti-Cu and Ti-Mn alloys slightly affects their relative density and significantly changes the nature of the phases composing each material. This includes the transformation of the typical lamellar structure into lamellar hypo-eutectoid structures as well as the formation of metastable phases. The response to the heat treatment and the phases formed are clearly influenced by the chemistry of the β eutectoid bearing binary Ti alloys. Performance comparable to those of thermomechanically hot forged alloys are nonetheless achieved via a simple heat treatment procedure.     

The effect of grain size and stability on ambient temperature tensile and creep deformation in metastable beta titanium alloys

The effect of grain size in the range of 100–500 μm on the ambient temperature tensile and creep deformation behavior was investigated in a metastable Ti–9.4 wt% Mn alloy at 95% yield stress. It was observed that, as grain size increases the creep strain increases, the slip lines become coarser and the density of slip increases. An interrupt creep test showed that new slip lines were generated with time and most of the deformation occurred during the first few hours of testing. The effect of β-phase stability was studied by comparing the creep and tensile behavior of Ti–9.4 wt% Mn in this study, with previously reported results obtained for Ti–14.8 wt% V and Ti–13.0 wt% Mn at ambient (room) temperature. The Molybdenum Equivalency, which is a measure of the stability of these alloys, are 9.9, 14.3, and 19.9, respectively. The main mode of deformation in Ti–9.4 wt% Mn alloy was observed to be slip. The modes of deformation changed with the increase in stability from slip accompanied by Stress Induced Plate formation to only slip. It was also found that metastable ω-phase was present in lower stable alloys, irrespective of the observed mode of deformation. At 95% yield stress, the amount of creep strain in 200 h was found to increase with a decrease in stability of the β-phase.     

Synthesis and grain growth kinetics of in-situ FeAl matrix nanocomposites（ Ⅰ ）： Mechanical alloying of Fe-A1-Ti-B composite powder

Three nanocrystalline alloys, FesoAlso, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 （molar fraction, %）, were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological changes of the milled powders were characterized by X-ray diffractometry（XRD）, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. The effects of different Ti, B additions on the structure and phase transformation in these alloys were also discussed. It is observed that the diffusion of AI, Ti, B atoms into Fe lattice occurs during milling, leading to the formation of a BCC phase identified as Fe（Al） or Fe（Al, Ti, B） supersaturated solid solution. Fe-based solid solution with nanocrystalline structure is observed to be present as the only phase in all the alloy compositions after milling. Furthermore, the contents of Ti, B affect the formation of mechanical alloying products, changes in the lattice parameter as well as the grain size.