Characteristic atom sequences of Nb-Mo alloys system in BCC structure and properties of disordered alloys

Comprehensively considering energy, volume and electronic structure of alloys, the ninth equation was determined as the interaction function of Nb-Mo alloys system in BCC structure on the basis of idea of systematic science of alloys, experimental lattice constants and heats of formation of disordered Nb（1-x）Mox alloys. The structural parameters and properties of Nb and Mo characteristic atoms sequences and corresponding characteristic crystals sequences were determined in Nb-Mo alloys system. The electronic structure and physical properties of disordered Nb（1-x）Mox alloys system were calculated according to concentration of characteristic atoms of disordered alloys. The change trend of physical properties is the same as that of electronic structure.

Thickness dependence of the anomalous Hall effect in disordered face-centered cubic FePt alloy films

The anomalous Hall effect in disordered face-centered cubic(fcc) FePt alloy films is experimentally studied. The longitudinal resistivity independent term of the anomalous Hall conductivity(AHC) increases and approaches saturation with increasing film thickness. The contribution of side jump scattering is suggested to decrease monotonically with increasing film thickness, which can be ascribed to the variation of the surface scattering with the film thickness. The sign of the skew scattering contribution to the AHC is opposite to that of the intrinsic contribution in the system.

Time-resolved Photoluminescence Spectra of Nominally Disordered GaInP Alloy

Luminescence decay and time resolved photoluminescence(TRPL) spectra are used for study on the transient luminescence process of the nominally disordered GaInP alloy. The luminescence decay of GaInP alloy shows the temperature and excitation intensity dependent characters. At 77 K and under high excitation intensity, the luminescence decay shows single exponential time dependence, while under low excitation intensity or at 300 K, the luminescence decay shows double exponential time dependence. The analysis indicates that this nominally disordered GaInP alloy actually exhibits a very weak degree of order. The blue shift of PL peak is observed in the TRPL spectra at 77 K, which is derived from the transfer of the carriers from the ordered domain to the disordered region of the alloy. At 300 K, due to the thermal quenching, the transfer is too weak to be observed. However, The recombination of the carriers between the ordered domain and the disordered region is still devoted to luminesce.

New atom movement mechanism for tracking path on disordering AuCuI(A_8^(Au)A_4^(Cu)) compound

Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure stabilization against changing temperature is attributed to the fact that the AAu8 and ACu4 potential well depths greatly surpass their vibration energies, which leads to the subequilibrium of experimental path. A new atom movement mechanism of AuCuI（AAuACu84）to change structure for suiting variation in temperature is the resonance activating-synchro alternating of alloy genes, which leads to heterogeneous and successive subequilibrium transitions. There exists jumping order degree, which leads to the existence of jumping Tj-temperature and an unexpected so-called ＂retro-effect＂ about jumping temperature retrograde shift to lower temperatures upon the increasing heating rate. A set of subequilibrium holographic network path charts were obtained by the experimental mixed enthalpy path method.

A new strategy to strength-toughen metals: Tailoring disorder

Metals have been mankind’s most essential materials for thousands of years.In recent years,however,innovation-driven development of major national security strategy and core areas of the national economy is highly impeded by a shortage of advanced higher-strength-toughness metals.One of the main reasons is that metals inherently exhibit the inverted-relationship of strength-toughness.The emergence of two types of disordered metals:amorphous alloys and high entropy alloys,provides a fully-fresh strategy for strength-toughening by tailoring the topological and/or chemical disorder.In this paper,we first briefly review the history of strength-toughening of metals,and summarize the development route-map.We then introduce amorphous alloys and high entropy alloys,as well as some case studies in tailoring disorder to successfully achieve coexisting high strength and high ductility/toughness.Relevant challenges that await further research are summarized in concluding remarks.

First principles study on the electronic structure and magnetism of Fe1-xCoxSi alloys

Electronic and magnetic properties of Fe1-xCoxSi alloys were investigated by using a full-potential linear augmented-plane-wave method based on density functional theory. Electronic structure calculation demonstrates that half-metallic property appears in the Fe-rich region of 0 〈 x ≤ 0.25, while the alloys turn out to be a magnetic metal for x 〉 0.25. The concentration dependence of the magnetic moment of the alloys can be understood by the fixed Fermi level at minority band in Fe-rich region, as well as at the majority band in Co-rich region. In Fe-rich alloys, the electronic structure and the magnetic properties at Fe site depend mainly on the spin-polarization of nearest neighbouring Co atoms, while in Co-rich alloys, these features at Co site arise mainly from the neighbours of Fe atoms.

Thermodynamic modeling of the La-Mg-Y system and Mg-based alloys database

As an example of the La-Mg-Y system, the method how to set up the themaodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases （liquid, body-centered cubic, face-centered cubic, hexagonal close-packed and double hexagonal close-packed） were modeled with the Redlich-Kister equation. The compound energy model has been used to describe the thermodynamic functions of the intermetallic compounds in the La-Mg-Y systems. The compounds Mg2Y, Mg24Y5, Mg12La, Mg17La2, Mg41Las, Mg3La and Mg2La in the La-Mg-Y system were treated as the formulae （Mg,Y）2（La,Mg,Y）, Mg24（La,Mg,Y）4Y, Mg12（La, Y）, Mg17（La,Y）2, Mg41（La,Y）5, Mg3（La,Mg,Y） and Mg2（La, Y）, respectively. A model （La, Mg,Y）0.5（La,Mg,Y）0.5 was applied to describe the compound MgM formed by MgLa and MgY in order to cope with the order-disorder transition between body-centered cubic solution （A2） and MgM with CsCl-type structure （B2） in the La-Mg-Y system. The Gibbs energies of individual phases were optimized in the La-Mg, La-Y and La-Mg-Y systems by CALPHAD technique. The projection of the liquidus surfaces for the La-Mg-Y system was predicted. The Mg-based alloys database including 36 binary and 15 ternary systems formed by Mg, Al, Cu, Ni, Mn, Zn and rare earth elements was set up in SGTE standard.

EAM Analysis of the Lattice Parameter Effect in Order-Disorder Transformation

The embedded atom method (EAM) was used to theoretically analyze the effect of the lattice parameter variation on the order-disorder transformation in binary alloys. Based on EAM, it is found that only one kind of order-disorder transition (second-order transition) exists for AB alloy. Three groups of order-disorder transformation can be observed for the A(3)B or AB(3) compounds. For group I, the order-disorder is a completely first-order transition. For group II, the order-disorder transformation is a classical first-order transition. For group III, the order-disorder transformation is found to be a second-order transition. The lattice parameter variations have a significant effect on E-2 coefficient, which is related to the ordering energy. These results are in good agreement with experiments.

Pt-Pd-Ni体系相图与热力学研究进展

铂基催化剂具有活性高、选择性好、电化学稳定性佳等优点,在工业催化和燃料电池领域具有非常重要的地位。然而,由于成本较高、可用性较低限制了其实际发展。因此,有必要优化铂基催化剂的利用率,设计低成本和高稳定性的铂基催化剂。本研究首先介绍了在燃料电池催化剂领域具有应用前景的Pt-Pd-Ni系合金电催化剂的发展和研究现状,然后详细介绍了Pt-Pd-Ni体系的三个二元系相图与热力学评估数据和研究进展,并对Pt-Pd-Ni三元系的一些实验研究进展和今后的研究工作提出展望,对不同相结构对催化性能的影响进行了分析和讨论。通过Pt-Pd-Ni系相图和相结构等的研究将为燃料电池用新型贵金属合金催化材料的设计及工业应用奠定理论和实验基础。

Accelerated intermetallic phase amorphization in a Mg-based high-entropy alloy powder

We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition.Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure.This transformation,characterized by the emergence of antisite disorder,lattice expansion,and the presence of nanograin boundaries,signifies a departure from the precursor intermetallic structure.Additionally,this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy.The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.

Research on properties of DO_3- and B2-type ordered alloys and disordered alloys in Nb-Mo alloy system in BCC structure

Based on the idea of systematic science of alloys, we derived the interaction equations of binary alloys in BCC structure in this paper. According to the basic information of characteristic atoms sequences and characteristic crystals sequences of Nb-Mo alloy system and the concentrations of characteristic atoms of Nb-Mo alloy system, the properties of DO3-Nb3Mo type ordered alloys, B2-NbMo type ordered alloys and DO3-NbMo3 type ordered alloys and disordered alloys were calcu-lated. The results show that the properties of ordered alloys exhibit stronger variations than those of disordered Nb(1-x)Mox alloys when approaching the stoichiometric ratio, whereas the opposite trend occurs when deviating from the stoichiometric ratio. The main reason is that the ordering degree is maximal at the stoichiometric ratio while it decreases linearly when deviating from stoichiometric ratio. On the contrary, the number of bonding electrons among atoms increases with the simultaneous decreasing of the nearly free electrons, which shortens the bond lengths and thus strengthens the crystal bonding.

透氢用钯合金的研究与开发

综述了钯合金成分和结构对透氢性能的影响。指出ＰｄＲＥ系合金，尤其是ＰｄＹ合金比实用化的Ｐｄ２５ａｔ％Ａｇ透氢性能优越。有序无序转变对钯合金的透氢性能有影响。ＰｄＲＥ合金中有序无序转变研究较多的是ＰｄＣｅ、ＰｄＧｄ合金，但它们的透氢速率却都不如ＰｄＹ合金。电阻测量的结果表明ＰｄＹ合金中存在Ｐｄ３Ｙ型的短程有序结构，有人又发现该合金中存在Ｐｄ７Ｙ型的长程有序结构，是由Ｌ１２型的Ｐｄ３Ｙ转化而来的。

有序的PdY合金的显微组织

本文观察了两种成分的钯钇合金，Ｐｄ（７－５～８．０）％ Ｙ（原子分数，下同）和Ｐｄ（８．０～８．５） ％ Ｙ的显微组织结构。将Ｐｄ粉和Ｙ粉在真空感应电炉中熔炼成成分合格的合金铸锭，经９５０℃×６ｈ 真空均匀化处理后，制成厚为０－０１９ｍ ｍ 的箔材，然后施行不同的热处理。利用光学、透射电子显微镜观察其组织与微观结构。结果表明，经退火的钯钇合金中存在有序相，出现了反相畴界。有序态的Ｐｄ８ ％ Ｙ合金将比无序态的透氢速率高。

LiMgPbSb型四元Heusler合金CoFeTiSb的半金属性及其无序效应

基于密度泛函理论的GGA计算,我们研究了LiMgPbSb型Heusler合金CoFeTiSb电子结构,发现CoFeTiSb在费米面处存在100%的自旋极化率,并且具有2μB的原胞总磁矩.此外,我们考虑了Co-Fe、Co-Ti和Fe-Ti交换无序对CoFeTiSb合金电子结构的影响,发现这三种交换无序均使得CoFeTiSb完全丧失了半金属性,在Co-Fe交换无序下,CoFeTiSb合金具有85%的自旋极化率,而在Co-Ti无序下,CoFeTiSb合金的自旋极化率只有5%.

Ti_2AlNb基合金热处理中的相结构与相变预测

运用相图计算技术,预测了名义成分为Ti-22Al-27Nb的Ti2AlNb基合金在热处理过程中的相结构与相转变,得到了该合金的相转变温度、相比例和各相的成分等重要信息,将材料热力学中的亚晶格模型和第一性原理总能计算相结合,对Ti2AlNb基合金中的主要组成相—O相(有序正交相)中的合金元素在各个亚晶格上的占位分数和有序化行为进行了深入研究,表明O相的有序-无序转变属于具有连续变化特征的二级相变,预测结果与现有实验结果相当吻合。

Pd－8at％Y合金的有序无序转变

探讨了Ｐｄ－８ａｔ％Ｙ合金的有序无序转变。利用高温电阻法、ＸＲＤ法检验了该类合金的有序无序转变温度及相组成。结果表明，该类合金中存在Ｐｄ３Ｙ型长程有序相。Ｐｄ—８．２２ａｔ％Ｙ经９２０℃淬火＋７５０℃退火所得的有序结构较强。Ｐｄ—７．５２ａｔ％Ｙ有序无序转变温度Ｔｃ＝７００±１０℃。

高活性B_4C-SiC超细复合粉体的制备及烧结

以B4C、SiC粗粉为原料,采用机械合金化制备高活性的B4C-SiC超细复合粉体。通过XRD、SEM、LPSA和IR等测试技术研究球料比、过程控制剂及球磨时间对复合粉体性能的影响,确定机械合金化制备B4C-SiC超细复合粉体的最佳工艺条件,研究机械合金化过程中粉体有序-无序转变过程。随后,采用热压烧结工艺验证复合粉体的烧结活性。结果表明:球磨机转速是250 r/min的条件下,球料比为30:1,过程控制剂为2wt%,球磨时间为120 h时,可获得晶格无序的B4C-50wt%SiC超细复合粉体;该复合粉体在1900℃,30 MPa热压条件下烧结1 h,其体积密度为2.62 g/cm3,达到理论密度的93%,比普通混合粉体在相同热压条件下获得样品的致密度提高了8.1%;机械合金化工艺制备的B4C-SiC超细复合粉体具有极高的烧结活性。

固态二元合金超额热力学函数的计算方法

基于Miedema二元合金生成热模型 ,结合自由体积理论 ,充分考虑超额熵 ,针对实际固态二元合金熔体 ,提出全浓度范围内的超额热力学函数的计算方法 ,分别推导出对有序、无序固态二元合金的全摩尔超额函数、偏摩尔超额函数、组元活度计算式·分别计算了固态无序合金Ag Au、有序合金Co Pt在 80 0K、1 2 73K温度下的各种超额热力学函数值 ,计算结果与实验值吻合良好·