碳化物特性对Ni3Al基表面强化复合材料组织与性能的影响

将真空常压烧结的方法制得的Cr3C2-Ni-Al和WC-Ni-Al复合焊丝氩弧堆焊于碳钢表面时,利用氩弧物理热和Ni-Al反应热,促使碳化物硬质颗粒与自生成的Ni3Al金属间化合物基体复合.XRD分析表明,在堆焊过程中两种焊丝中的Ni,Al均化合反应生成Ni3Al金属间化合物.微观组织与硬度试验表明,受各自物理特性(密度、熔点)的影响,两种碳化物硬质相在Ni3Al基体中分布均匀程度不同,其强化效果也迥异:WC仍以原始的大颗粒形态偏聚于焊层层间界面处,而起不到弥散强化作用;Cr3C2则发生分解,并反应析出条块状的Cr7C3相,均匀分布于Ni3Al基体中,很好地强化了基体材料.Cr7C3/Ni3Al复合材料的室、高温硬度远高于传统高温耐磨材料stellite合金.该合金有望成为一种新型的高温耐磨表面强化材料.     

含微量Y的Ni-20Al-30Fe定向合金的研究

一、引言 近年来,在金属间化合物中,特别是Ni—Al系长程有序金属间化合物作为高温结构材料应用前景日趋明显。B_2型Ni—Al化合物具有高熔点、低密度、高热传导性以及优良的抗氧化性能等特点,作为航空航天工业耐热结构材料具有更大潜力。但由于它低温塑性差,中温、高温强度低,限制了它的应用。为了改善低温塑性和提高中温、高温的强度,人们正进行各方面的努力。In-oue等人研究了快速凝固法制备Ni—20Al—30Fe线材合金性能,Sumit Guha等人也对同一成分合金通过热挤压成型工艺研究了该挤压合金的室温性能。结果表明,Fe的加入可提高B_2型NiAl合金的室温塑性,但对高温性能未作报道,这一较好的结果说明了Ni—Al—Fe系合金是值得重视和研究的。在高温合金和在Ni_3Al金属间化合物的研究中发现,少量的稀土元素Y的加入对合金塑性和抗氧化性有好处。为此,我们试图通过加入微量稀土元素Y(0.01wt％)和采用定向结晶工艺,达到提高Ni—20Al—30Fe合金的强度与塑性的目的。     

Ni-Al系金属间化合物价电子结构与性能分析

NiAl和Ni3Al金属间化合物熔点高、密度低,具有较好的热传导性和良好的抗氧化性,是航空航天领域很有潜力的高温结构材料.运用固体与分子经验电子理论分析了NiAl和Ni3Al金属间化合物的价电子结构,并从电子结构层次初步探讨了NiAl和Ni3Al金属间化合物的强度、稳定性、室温脆性及熔点等问题.计算结果表明,化学计量比的NiAl和Ni3Al的脆性因子均小于0.08,室温下表现为本征脆性,NiAl的脆性比Ni3Al的脆性大;NiAl的熔点和强度均比Ni3Al的高,稳定性比Ni3Al的差.     

合金元素在Ni3Al金属间化合物中的作用

介绍了Ni3Al基金属间化舍物研究的现状和前景.由于Ni3Al基金属间化合物具有高熔点、低密度和良好的抗氧化性等性能,长期以来作为高温结构的候选材料而得到了广泛的关注,但是Ni3Al在室温下塑性差和高温时强度低限制了它的使用.采用合金化的方法可使Ni3Al基金属间化合物的性能得到改善,着重介绍了合金元素在Ni3Al基金属间化合物中的作用.     

促进铝化物科研成果向生产转化—美国GAMI的措施

铝化物是一种有着广阔应用前景的高技术新材料,主要包括镍、铁和钛的铝化物,例如Ni_3Al、FeAl和TiAl等,其主要用途是作高温结构材料。由于这类高温材料是具有有序结构相的金属间化合物,故又称高温有序合金或高温金属间化合物。与镍基高温合金相比,由于这类材料的高温性能更好,可在更高的温度下工作,比重轻,抗铝腐蚀能力     

稀土钇对2519合金组织及耐热性能的影响

采用X射线、光学显微镜、扫描电镜及透射电镜等手段研究了微量稀土Y对2519合金的显微组织及耐热性能的影响.结果表明,在2519合金中Y元素与Cu,Al元素主要形成Al6Cu6Y金属间化合物,并沿晶界分布.这些金属间化合物有效阻碍高温时基体的变形和晶界的移动,提高合金高温强度.添加0.20%Y(质量分数)可使合金200℃时的抗拉强度提高30%,但伸长率有所下降.Y含量的进一步增加,含Y化合物聚集长大成块,合金室温及高温力学性能降低.同时发现,微量的Y细化了合金的再结晶组织,细化了合金强化相θ′相.添加0.10%Y时可使合金的室温强度提高20MPa.     

激光合成Ni-Cr-Al+12%TiC涂层的显微组织及耐磨性研究

在不锈钢基材上通过激光合成Ni-Cr-Al-Co-X(X=Mo、W、Nb、Ti、C) 12%TiC粉末制备出组织均匀且与基体间完全冶金结合的无缺陷的涂层,其中组织主要为金属间化合物Ni3Al-Ni0.58Al0.42及其增强相TiC.利用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、显微硬度计和磨损试验机对涂层的组织、相结构、硬度及耐磨性进行了分析和测试.结果显示:复合材料涂层的主要组织为TiC增强相、金属间化合物Ni3Al及大量Ni0.58Al0.42相;其组织均匀,与基体之间为完全冶金结合,具有硬度高、抗粘着摩损能力强的特点,在滑动干摩擦实验条件下表现出优异的耐磨性.     

硬质相对冷喷涂FeAl金属间化合物涂层性能的影响

FeAl金属间化合物具有优良的物理性能和力学性能,但其室温塑性和断裂韧性低,限制了其工程应用.利用机械合金化制备了Fe(Al)固溶体合金粉末及Al2O3,WC硬质相增强的复合合金粉末,通过冷喷涂沉积涂层并结合后热处理原位反应制备了FeAl金属间化合物涂层及其复合涂层.利用扫描电镜(SEM)、X射线衍射仪(XRD)及显微硬度仪等研究了硬质相对球磨粉末组织结构、冷喷涂FeAl金属间化合物涂层组织结构及性能的影响.结果表明.硬质相可显著加速球磨粉末内部层状结构的细化程度,喷涂态涂层具有不同于传统热喷涂涂层的层状组织结构,热处理可实现喷涂态涂层中Fe(Al)固溶体向FeAl金属间化合物的原位转变,致使层状结构消失,获得无粒子界面的FeAl金属间化合物涂层,弥散分布的硬质相可显著提高冷喷涂FeAl金属间化合物涂层的强化稳定性.     

激光合成TiC/Ni-Al复合材料涂层组织及耐磨性研究

在不锈钢基材上通过激光合成Ni-Cr-Al-Co-X(X=Mo、W、Nb、Ti、C) TiC粉末,制备出金属间化合物Ni3Al-Ni0.58Al0.42,获得了组织均匀且与基体间完全冶金结合的无缺陷涂层.利用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、显微硬度计和磨损试验机对涂层的组织、相结构、硬度及耐磨性进行了分析和测试.结果表明,复合材料涂层主要组织为TiC增强相、金属间化合物Ni,Al及大量Ni0.58Al0.42相;其组织均匀,与基体之间为完全冶金结合;复合材料涂层具有硬度高、抗黏着摩损能力强的优点,在滑动干摩擦试验条件下表现出优异的耐磨性能.     

Al元素对310S耐热钢组织和力学性能的影响研究EI北大核心

通过WS-4非自耗真空电弧炉熔炼制备了加Al 2%~10%(质量分数)的耐热钢310S(Cr25Ni20),用光学金相显微镜观察了金相组织,用EPMA-1600电子探针分析了组织中各元素的分布,结合D8 ADVANCE型X射线衍射确定了合金中的相组成,并进行了室温压缩和硬度力学性能试验。结果表明,随着铝含量增加,碳化物由连续条状转变为质点状;Al元素固溶于基体中,基体相为γ相;当Al含量大于6%时,基体相为α相,合金脆性大幅提高,合金由塑性材料转变为脆性材料。     

Investigation of the thermo-stimulated surface segregation in the ternary Co-Cr-Mo alloy by means of Ionization Spectroscopy

Ionization Spectroscopy has been used to study thermo-induced surface segregation in the near-surface region of the ternary Co-Cr-Mo alloy. For the non-annealed alloy the Mo atoms preferred segregation in the outermost layers and Cr atoms segregation in the underlying layers of surface was observed at room temperature. Heating of the alloy promotes increasing of Co concentration and decreasing of Mo concentration in the near-surface region. For the annealed alloy the insignificant Mo atoms segregation on the outermost layers and enrichment with Co and Cr atoms in underlayers are displayed. The present results are compared with several theories of segregation.     

团簇线规律在合金相结构中的应用

研究了Zr-Al-Ni体系中合金相的团簇结构规律,指出了在合金相结构中团簇之间以不同方式共享原子的事实.共享后有效团簇的成分就是相成分,这类相称为非团簇相;共享后的有效团簇必须加上连接原子才能构成空间相结构,这类相称为团簇相.在典型的非晶形成体系Zr-Al-Ni中,团簇相有3个:AlNiZr-Fe_2P结构,Al_2NiZr_6-InMg_2结构和Al_5Ni_3Zr_2-Mn_(23)Th_6结构.对于团簇相的成分和结构,可以用模型(相成分=[有效团簇]+(连接原子))来解释.这种用来解释非晶成分的团簇线规律是对合金相成分和结构的一种全新理解.由于团簇的形成来源于组元间的负混合焓,这应该是合金相结构中普遍存在的规律.     

Preparation of gallium nitride from gallium–magnesium alloy powders

Ga–Mg alloy powders were introduced to synthesise GaN powders with flowing ammonia. When the magnesium percentage in the alloy was 25?wt-% or below and the reaction temperature was about 750°C, all Ga atoms in the alloy were transformed into GaN, and the diameter of the GaN powders was about 40?nm. For the Ga–Mg alloy powders with a diameter ranging from 37 to 75?µm ammoniated at 750°C, only 3?h were spent to transform all the Ga atoms into GaN, indicating that the strategy suggested in this study was effective to produce GaN powders.     

铈对Fe-Cr-Ni-Nb-Ti-Al-W合金晶界MC相组成的影响

采用EDS研究了铈对铁基合金Fe Cr Ni Nb Ti Al W晶界析出相MC中M组成的影响。结果表明,随着合金中铈含量的增加,晶界MC相中铌量增加,而钛量相对下降。此结果证明,由于铌与碳的亲和力较钛大,当晶界附近的钛、铌等替代式溶质原子被铈原子驱逐并与碳结合时,有更多的铌参与了晶界MC相的组成。     

From the interface energy to the solubility limit of aluminium in nickel from first-principles and Kinetic Monte Carlo calculations

We developed a way to predict the solubility limit of solute atoms in a binary alloy using a Kinetic Monte Carlo algorithm. The idea is to use the interface energies calculated by first-principles calculations to parameterize the pair interaction energies used in the Kinetic Monte Carlo algorithm. In order to validate this method, it was tested on a very well known case: the Ni-Al alloy. We found that the calculations are in very good agreement with the previously calculated phase diagrams.     

Simulation of clusters formation in Al-Cu based and Al-Zn based alloys

A Monte Carlo computer simulation is adopted to investigate the role of micro-alloying elements Mg and Ag in Al-Cu and Al-Zn alloys. Small amount additions of Mg to the Al-Cu alloy markedly retard the formation of Cu clusters due to the preferential trapping of free-vacancies available for Cu diffusion. On the other hand, additions of Mg to the Al-Zn alloy promote the formation of Zn clusters due to the preferential Mg-Zn interaction. As for the effect of Ag, it is found that, in both Al-Cu-Mg and Al-Zn-Mg alloys, Ag atoms are preferentially bounded to Mg-Cu-vacancy or Mg-Zn-vacancy complexes. However, in Al-Cu-Mg alloy Ag atoms interact with Mg, while in Al-Zn-Mg alloy they interact with both Mg and Zn.     

Patchy multishell segregation in Pd-Pt alloy nanoparticles

Chemical ordering in face-centered-cubic-like PdPt nanoparticles consisting of 38-201 atoms is studied via density-functional calculations combined with a symmetry orbit approach. It is found that for larger particles in the Pd-rich regime, Pt atoms can segregate at the center of the nanoparticle (111) surface facets, in contrast with extended systems in which Pd is known to segregate at the surface of alloy planar surfaces. In a range of compositions around 1:1, a novel multishell chemical ordering pattern was favored, in which each shell is a patchwork of islands of atoms of the two elements, but the order of the patchwork is reversed in the alternating shells. These findings are rationalized in terms of coordination-dependent bond-energy variations in the metal-metal interactions, and their implications in terms of properties and applications of nanoscale alloy particles are discussed.     

A study on a Ti52Ni47Al1 shape memory alloy

The Ti₅₂Ni₄₇Al₁ alloy has 16% volume fraction Ti₂Ni particles in the B2 matrix with Ti₂Ni particles having a higher Al content than the B2 matrix. Transformation temperatures M^* and A^* of this alloy are lower than those of the Ti₅₁Ni₄₉ alloy due to the solid solution of the Al atoms. M^* and A^* decrease with increasing aging time at 400°C because the Al atoms diffuse slightly from the Ti₂Ni to the B2 matrix. The hardness increment of this alloy is more than that of the Ti₅₁Ni₄₉ alloy under the same degree of cold rolling. At the same time, M^* and A^* of this alloy can be more depressed by thermal cycling than those of the Ti₅₁Ni₄₉ alloy, especially in the first ten cycles. All of these features result from the fact that this alloy has a higher inherent hardness due to the solid solution of the Al atoms. This also causes the R-phase transformation to be more easily promoted by both cold rolling and thermal cycling in this alloy. The strengthening effects of cold rolling and thermal cycling on the M^* (Ms) temperature of this alloy follows the expression Ms = T₀–K_y, in which K values are affected by different strengthening processes. It is found that the higher the inherent hardness of the TiNi and TiNiX alloys, the higher the K values they have.     

Diffusion distribution of 57Co atoms in nanocrystalline Co79Nb14B7 alloy

Distribution of ⁵⁷Co atoms in a nanocrystalline Co₇₉Nb₁₄B₇ alloy after annealing at different temperatures was studied by means of ⁵⁷Co emission Mössbauer spectroscopy. After annealing below the recrystallization temperature, the diffusing ⁵⁷Co atoms were found in all phases expected to be present in the nanocrystalline alloy. They do not prefer the intergranular phase. Paths of diffusing atoms are probably close to interfaces between crystallites (grain boundaries) and/or intergranular phase. With increasing annealing temperature, when the nanocrystalline state transforms into a coarse polycrystal, the ⁵⁷Co atoms occupy regular sites in the bulk Co and Co₃B phases.     

A floating magnet model for simulating metals and alloys

A floating magnet model [5, 6] originally devised for simulating effects in superconductors has been modified to simulate metal and alloy lattices. The model shows grain boundaries, edge dislocations and point defects in the metal lattice, demonstrating the pinning of dislocations by impurity atoms and the drift of impurities to grain boundaries. Although the alloy was disordered for most concentrations, a stable ordered square lattice was formed readily at equal proportions of the two atoms. Defects, particularly dislocations, were more complicated in the ordered alloy than in the simple metal.