Au_3Cu-亚格子系统的合金基因Gibbs能配分函数和平衡全息网络相图(英文)

以Au3Cu-亚格子系统为例,介绍了3项发现:第一,至今阻碍金属材料科学进步的第四大障碍是研究者们尚未认识到一个真正的合金相Gibbs能函数应由合金基因序列和它们自己的Gibbs能级序列构建的Gibbs能配分函数导出。第二,建立合金基因Gibbs能配分函数的六条规则,特别证明了计算合金组态熵的简并因子中结构单元占居Gibbs能级的概率应按照组元占居格点的概率方式简并;第三,以前研究者从未预料到的主要特征:具有一条没有有序相和无序相共存区的单相相界线;相界线顶点成分和温度远偏离Au3Cu化合物临界点的成分和温度;在0 K时,Gibbs能随成分变化曲线上的最低点成分远偏离Au3Cu化合物的成分;Au3Cu-型长程有序合金的理论极限成分范围由第一跳变有序度决定。     

Au3Cu-亚格子系统的合金基因Gibbs能配分函数和平衡全息网络相图（英文）

以Au3Cu-亚格子系统为例,介绍了3项发现:第一,至今阻碍金属材料科学进步的第四大障碍是研究者们尚未认识到一个真正的合金相Gibbs能函数应由合金基因序列和它们自己的Gibbs能级序列构建的Gibbs能配分函数导出。第二,建立合金基因Gibbs能配分函数的六条规则,特别证明了计算合金组态熵的简并因子中结构单元占居Gibbs能级的概率应按照组元占居格点的概率方式简并;第三,以前研究者从未预料到的主要特征:具有一条没有有序相和无序相共存区的单相相界线;相界线顶点成分和温度远偏离Au3Cu化合物临界点的成分和温度;在0 K时,Gibbs能随成分变化曲线上的最低点成分远偏离Au3Cu化合物的成分;Au3Cu-型长程有序合金的理论极限成分范围由第一跳变有序度决定。     

FP-SSA框架中Au_3Cu型有序合金相的特征原子势能配分函数

介绍以第一原理合金电子理论为基础的系统合金科学(FP-SSA)框架中Au3Cu型有序合金的特征原子势能(CAPE)配分函数。主要创新内容如下:以基本原子团{AiA u·[(I-i)Au,iCu]}和{AiC u·[(I-i)Au,iCu]}序列的中心特征原子Ai Au和AiC u为结构单元序列,替代原子对和原子团,建立了合金相的特征原子排列模型;以配位原子团[(I-i)Au,iCu]对作用于特征原子势场影响的方式替代原子对能量相互作用和原子团能量相互作用方式,以特征原子势能能级代替原子对能级和原子团能级,建立了合金相的特征原子势能相加定律,计算合金相及其组元的平均势能;在特征原子排列的简并因数与特征原子势能能级一致的条件下建立CAPE配分函数和计算组态熵。此函数揭示了当今流行的固溶体理论的不足之处,为建立特征Gibbs能配分函数奠定了基础。     

高强度钯基弹性合金之研究

研究两种Pd合金的力学、电学性能和组织结构.两种合金具有适中电阻率、低的电阻温度系数和对Cu热电势.与铍青铜、Palliney-7六元合金及Pt-20Ag等著名弹性合金的性能对比,具有高强度和高硬度.HSP-1合金的弹性模量与铍青铜相当,强度约高一倍.细晶粒基体结构、溶质的固溶强化、第二相呈均匀分布的纤维结构、时效过程中强的晶格畸变与斜方时效相的形成,是合金在淬火态、加工态和时效态呈高强度的原因.两种合金可以代替Pt-20Ag、Palliney-7等合金作弹簧、弹性电刷、张丝、滑动接点等材料使用,从而可以节省Pt和Au.     

Au-15Cu-10Ni合金时效强化机制研究

常用作电接触材料的Au Cu Ni合金在时效过程中会得到强化,硬度明显增加。采用真空高频熔炼得到Au-15Cu-10Ni合金,对轧制得到的片材进行不同条件下的时效处理,研究其微观组织、晶体结构和力学性能变化。结果表明,150~250℃范围内时效硬化效果显著,并且随温度升高硬度值提高,时效过程中生成的Au CuI有序相是造成硬度提高的主要原因。在200℃的条件下时效2.78 h后,晶粒表面出现了明显的条纹状,组织发生有序转变;时效时间延长至5 d后有序转变完成,晶体结构由fcc转变为fct结构,晶胞发生体积收缩,导致晶界明显宽化。     

Cu-Ag合金强度与弹性模量在组织纤维化过程中的变化

采用冷拉拔制备了Cu-6％Ag及Cu-12％Ag纤维相复合强化合金线材，研究了组织纤维化对Cu—Ag合金强度与弹性模量的影响。随变形程度的增加，合金抗拉强度和弹性模量在明显升高后趋于饱和。Cu-12％Ag合金比Cu-6％Ag合金有更高的应变硬化速率和抗拉强度。在较低变形程度范围内，Cu-6％Ag合金的弹性模量高于Cu-12％Ag合金。在较高变形程度范围内，Cu-6％Ag合金的弹性模量低于Cu-12％Ag合金。纤维化组织中的高密度晶体缺陷使得两种Ag含量的合金弹性模量均低于理论预测值。合金的强度和弹性模量主要取决于共晶体数量、相界面密度、变形抗力及两相之间的变形协调行为。     

时效处理对Cu-3Ti-3Ni合金组织与性能的影响（英文）

研究了时效处理对Cu-3Ti-3Ni合金组织与性能的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)对Cu-3Ti-3Ni合金的组织和析出相进行了表征,并对其硬度、导电率和弹性模量进行了测试。结果表明:Cu-3Ti-3Ni合金时效处理后析出Ni_3Ti及β'-Cu_4Ti相。随着时效时间的延长,部分合金元素回溶于Cu基体,连续的亚稳定β'-Cu_4Ti相向不连续的稳定Cu3Ti相转变。Ni_3Ti相及β'-Cu_4Ti相的析出减少了Ti原子的固溶,导致导电率升高。经过合适的时效处理,Cu-3Ti-3Ni合金中的Ni_3Ti相及连续的亚稳定β'-Cu_4Ti相析出完全,导致硬度升高,但时效处理对合金弹性模量影响不大。在本实验范围内,Cu-3Ti-3Ni合金的最佳时效处理工艺是300℃时效2 h后炉冷,随后450℃时效7 h炉冷。Cu-3Ti-3Ni合金的HV硬度、导电率及弹性模量分别是1.83 GPa、31.34%IACS(国际退火铜标准)及148.62 GPa。     

时效处理对Cu-3Ti-3Ni合金组织与性能的影响

本文研究了时效处理对Cu-3Ti-3Ni合金组织与性能的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)对Cu-3Ti-3Ni合金的组织和析出相进行了表征,并对其硬度、导电率和弹性模量进行了测试。结果表明：时效处理后析出Ni3Ti及 β''-Cu4Ti相。随着时效时间的延长,部分合金元素回溶于Cu基体,连续的亚稳定β''-Cu4Ti相向不连续的稳定Cu3Ti相转变。Ni3Ti相及β''-Cu4Ti相的析出减少了Ti原子的固溶,导致导电率升高。经过合适的时效处理,Cu-3Ti-3Ni合金中的Ni3Ti相及连续的亚稳定β''-Cu4Ti相析出完全,导致硬度升高,但时效处理对合金弹性模量影响不大。在本实验范围内,Cu-3Ti-3Ni合金的最佳时效处理工艺是 300°C时效2 h后炉冷,随后450 °C时效7 h炉冷。Cu-3Ti-3Ni合金的硬度、导电率及弹性模量分别是183 HV、31.34 % IACS (国际退火铜标准)及148.62 GPa。     

原子有序度对Zr55Al10Ni5Cu30非晶合金等温晶化过程的影响

通过改变母合金铸锭的重熔次数和熔体冷却速率获得3种具有不同原子有序度的Zr55Al10Ni5Cu30块体非晶合金,并采用差示扫描量热仪研究了原子有序度对该合金等温晶化过程的影响。结果表明,在等温晶化条件下,原子有序度的增加使Zr55Al10Ni5Cu30块体非晶合金孕育期明显减小;对晶化相的形核和长大机制几乎没有影响,均为形核速率随时间增加的扩散控制的三维长大;使Avrami指数出现一定程度的减小。     

合金元素对Zr基大块非晶晶化行为的影响

利用准晶的共轭结构模型构造出了Zr基非晶合金中准晶相的原子结构模型,用递归方法研究了合金元素对非晶晶化过程的影响.结果表明:Zr基非晶合金析出的准晶相存在Zr6Ni,Ni6Zr2种结构,Ni6Zr结构优先析出;合金元素Ag,Pd,Pt,Au固溶于准晶中时,占据Cu,Ni原子的位置,增大近邻原子间的相互作用,这从电子理论角度解释了合金元素Ag,Pd,Pt,Au稳定地促进二十面体准晶(I)相析出的事实.     

Infrared brazing of Ti50Ni50 shape memory alloy using gold-based braze alloys

Infrared brazing Ti₅₀Ni₅₀ shape memory alloy using pure Au and Au-20Cu as the fillers has been investigated. The Au-rich and Au₄Ti phases, and Au₂TiNi, AuCu and Ni₃Ti phases are formed in the brazed joints using Au filler and Au-20Cu filler, respectively. The bending test shows the shape memory effect of brazed joint using Au filler is superior to that using Au-20Cu filler because the detrimental AuCu and Ni₃Ti phases exist in the latter case.     

Au—Cu系中无序和有序相的晶格常数

依据合金特征晶体理论,固溶体中组元的原子状态分裂成若干特征原子状态,固溶体的晶格常数可由特征晶体的晶格常数相加定律,特征原子体积相加定律的特征原子状态相加定律求得,介绍了无序二元固溶体的９种晶格常数函数;确定了无序Ａｕ－Ｃｕ合金及其元的晶格常数函数;预计了Ａｕ３Ｃｕ,ＡｕＣｕ,ＡｕＣｕ３和相应有序合金随成分变化的晶格常数。理论值与实验符合较好。     

Age-hardening characteristics of a dental low-carat gold alloy with dual hardener system of In and Cu

The age-hardening characteristics of a dental low carat gold alloy with a dual hardener system of indium (In) and Cu (33.9 Au–26.2 Ag–20.28 Cu–9.8 Pd–7.8 In–2 Zn (at%)) were examined by observing the age hardenability and related phase transformation, microstructural changes and elemental distribution during the aging process at 400°C. The dual hardener system by the use of both In and Cu provided more powerful hardening effect compared to a single-hardener system of In or Cu, without the formation of a AuCu type ordered phase. The alloy showed apparent initial hardening, which was attributed to the pre-precipitation or zone formation by the help of quenched in excess vacancies. During the constant increase in hardness, the single parent phase separated into three phases, Au–Ag-based phase, Au–Cu-based phase containing Pd and In, and InPd-based phase, through a metastable state. Indium which was added as one of the hardeners induced initial grain boundary precipitation, followed by an expansion of the lamellar structure, which was responsible for softening. The alternative lamellar structure was composed of a Cu-rich layer (Au–Cu-based phase containing Pd and In) and an Ag-rich layer (Au–Ag-based phase) replaced partly by the InPd-based phase. Separation of the Ag-rich layer from the Cu-rich layer is based on the miscibility limit of Ag and Cu due to their eutectic property.     

金银铜合金的相结构分析

对Au-20Ag-10Cu合金进行了X射线衍射、差热分析和扫描电子显微镜观察。结果表明,合金在280~300℃时效发生有序化转变,形成AuCu有序相;在400℃时效发生调幅分解,形成富金固溶体和富银固溶体。计算获得了各物相的晶格常数,测得有序化和调幅分解反应的开始温度分别为245.4℃和321.0℃。     

Solid state transformations of Au-Cu-Pt alloys studied by in-situ X-ray synchrotron radiation and DSC

Seven alloys of the ternary Au-Cu-Pt system, containing 75 or 76.5 wt.% Au with 0–15 wt.% Pt and heat-treated to a fully ordered condition, are examined using in-situ synchrotron radiation to determine transformation temperatures and phases formed, and to investigate mechanisms of ordering and disordering. These experiments are complemented by differential scanning calorimetry. Diffraction data show that the alloys can be separated into three groups according to their stable low-temperature ordered phase(s), namely L1₀, L1₂, or the two combined. Platinum increases transformation temperatures in comparison with binary AuCu, two-phase ordered alloys showing the highest transformation temperatures. Details of the evolution of the X-ray diffraction peak structures upon heating and cooling point to significant differences between mechanisms of disordering and ordering: whereas ordering visibly proceeds at significant undercooling by nucleation and growth, disordering appears, from the visible shifts in peak position, to progress in more homogeneous fashion within the alloy.     

AuCu双金属纳米颗粒的制备、表征及性能探究

采用水热法制备AuCu双金属纳米颗粒,并用X射线衍射(XRD)、透射电镜(TEM)和紫外可见光谱(UV-Vis)进行表征,初步研究了其对4-硝基苯酚(4-NP)还原的催化性能和光热效应。结果表明,制备时不同的AuCl_4~-/Cu~(2+)摩尔比(r_(Au))可以调控AuCu双金属纳米颗粒的组分和形貌,XRD和吸收光谱特征随r_(Au)的增加表现出更明显的金的特征,r_(Au)0.5时得到的颗粒具有典型的核-壳结构;核-壳结构的AuCu双金属纳米颗粒对4-NP还原表现出更好的催化活性,受光热效应影响,532 nm激光照射能够加强催化活性;在激光辐射作用下,不同AuCu双金属纳米颗粒具有相似的光热效应。     

Age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental Au–Ag–Cu–Pd–Zn alloy

The age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental casting gold alloy composed of 56Au–25Ag–11.8Cu–5Pd–1.7Zn–0.4Pt–0.1Ir (wt.%) were elucidated by characterizing the age-hardening behaviour, phase transformations, changes in microstructure and changes in element distribution. The fast and apparent increase in hardness at the initial stage of the aging process at 400°C was caused by the nucleation and growth of the metastable Ag–Au-rich phase and the Cu–Au-rich phase by the miscibility limit of Ag and Cu. The transformation of the metastable Ag–Au-rich phase into the stable Ag–Au-rich phase progressed concurrently with the ordering of the Cu–Au-rich phase into the AuCu I phase through the metastable state, which resulted in the subsequent increase in hardness. The further increase in hardness was restrained before complete decomposition of the parent α₀ phase due to the initiation of the lamellar-forming grain boundary reaction. The progress of the lamellar-forming grain boundary reaction was not directly connected with the phase transformation of the metastable phases into the final product phases. The heterogeneous expansion of the lamellar structure from the grain boundary caused greater softening than the subsequent further coarsening of the lamellar structure. The lamellar structure was composed of the Ag–Au-rich layer which was Cu-, Pd- and Zn-depleted and the AuCu I layer containing Pd and Zn.     

Investigation of the Partial Constitution Diagram Ti−TiAu<Subscript>2</Subscript>

Ti?Au alloys in the composition interval 0 to 66 2/3 atomic pet Au have been studied over a temperature range from 400° to 1500°C. A partial phase diagram has been established from micrographic and macroscopic observations. All intermediate phases, Ti₃Au, TiAu, and TiAu₂, exhibit open melting maxima. It has been observed that small additions of gold lower the allotropic transformation temperature of titanium. The β solid solution decomposes eutectoidally to α solid solution plus Ti₃Au. The solubility of gold in α solid solution decreases with temperature.     

Hyperfine interactions on iron nuclei in the BCC and fractally decomposed BCC/FCC mixed phase iron–gold alloys

Iron–gold alloys for the gold concentration ranging from 1 at.% till 70 at.% were investigated by means of the ⁵⁷Fe-14.4 keV Mössbauer spectroscopy, X-ray diffraction and scanning electron microscopy. Samples were prepared by arc melting of the elements, and investigated as cast and after annealing. A single BCC phase is obtained for the gold concentration up to about 3 at.%, while for the higher gold concentration one obtains mixed phase samples containing BCC and FCC phases both. The BCC phase is ferromagnetically ordered at room temperature. Contributions to the charge and spin density on iron atoms in the BCC phase due to the gold impurities were determined up to the second neighbors. The FCC phase is either magnetically ordered at room temperature or it is paramagnetic at the above temperature depending upon iron concentration, as the magnetic transition temperature is increasing with the increasing iron concentration. BCC/FCC mixed phase samples are characterized by very small crystallites (nanoparticles) of both phases. These nanoparticles form hierarchical fractal structures on the scale ranging from more than 1 mm till less than 30 nm.     

Hardening and overaging Mechanisms in an Au-Ag-Cu-Pd alloy with In additions

Hardening and overaging mechanisms were examined in a semi-precious Au−Ag−Cu−Pd dental alloy with small amounts of In, Zn and Ir. The alloy showed maximum age-hardenability at the aging temperature of 400°C. The hardness value increased to reach the maximum value, and then decreased continuously with aging time. In the early stage of aging process, the matrix of the single α₀ phase separated into the α₁ and AuCu I phases, and the fine InPd-based precipitates containing Zn and Cu formed at the grain boundaries. During further aging, the grain boundary precipitates grew toward the grain interior. In overaged specimens, the original matrix was replaced by the coarse lamellar structure composed of the AuCu I phase containing Pd and Zn and the Ag−Au-based α₁ phase of Cu-, Pdand Zn-depleted. The hardness increase in the early stage of aging process was caused by the nucleation of the InPd-based phase and the AuCu I phase in the ga₀ matrix; this introduced significant lattice strains into the interface with the matrix. The hardness decrease in the latter stage of aging process was caused by the formation and coarsening of the lamellar structure composed of the α₁ phase and the AuCu I phase. The minor constituent, In formed InPd-based grain boundary precipitates prior to the lamellar structure formation of α₁ and AuCu I.