热处理对Al2O3f/Mg-6Al-1Nd-1Gd复合材料组织演变与蠕变性能的影响

采用光学显微镜、扫描电镜、X射线衍射仪、EDS能谱分析等手段研究了不同热处理态Al₂O_3f/Mg-6Al-1Nd-1Gd复合材料在200℃、70 MPa条件下压缩蠕变前后金属间化合物的变化情况以及蠕变性能差异。结果表明：Al₂O_3f/Mg-6Al-1Nd-1Gd复合材料中的金属间化合物主要可分为β-Mg₁₇A1₁₂、Al₂(Nd,Gd)、Al₁₁(Nd,Gd)₃和Mg₂Si四种。复合材料经420℃+24 h固溶处理后,β-Mg₁₇A1₁₂相和Al₁₁(Nd,Gd)₃相几乎完全消失,而经T6处理后,又会重新析出。其中,β-Mg₁₇A1₁₂相呈针状或块状弥散分布于晶内,而Al₁₁(Nd,Gd)₃相则呈...     

不同Al2O3含量的Al2O3/Cu复合材料的热变形行为

为探究Al₂O₃含量对Al₂O₃/Cu复合材料热变形行为的影响，采用内氧化法制备了3种Al₂O₃含量(0.28、0.66和1.13 mass%)的Al₂O₃/Cu复合材料，通过热模拟实验对其热变形行为进行了研究。结果表明：在823、923和1223 K时，随着Al₂O₃/Cu复合材料中Al₂O₃含量的增加，复合材料的峰值应力逐渐增大；显微组织观察发现，由于1.13 Al₂O₃/Cu复合材料内动态软化积累程度最大，导致其在1023和1123 K下出现了峰值应力下降现象。经热挤压后，在热变形过程中Al₂O₃/Cu复合材料的软化效果以动态回复为主。同时，发现0.28 Al₂O₃/Cu和0.66 Al     

Al-8.0Zn-2.0Mg-2.1Cu合金均匀化过程中Al2CuMg相的消除

采用光学显微镜(OM)、扫描电镜(SEM)、电子探针显微分析(EPMA)、X射线衍射(XRD)以及差示扫描量热仪(DSC)研究了一种高合金化Al-8.0Zn-2.0Mg-2.1Cu(wt%)合金在均匀化过程中难溶相Al₂CuMg的形成以及实现其充分溶解的工艺。结果表明:铸态时,合金中主要的非平衡凝固相为Mg(Zn, Al, Cu)₂相,Zn、Mg、Cu元素偏聚严重。经过470 ℃×40 h一级均匀化后,虽然Mg(Zn, Al, Cu)₂相逐渐回溶至基体中促进了合金中枝晶网络的基本消除,但合金中形成了一种耐高温的有害相Al₂CuMg。进一步采用485 ℃×14 h的高温均匀化工艺实现了合金中耐高温相Al₂CuMg的充分回溶。扩散动力学分析表明,470 ℃×40 h+485 ℃×14 h的双级均匀化工艺足以使合金中的非平衡相回溶至基体中。     

Al-Ca-Fe合金中Al10CaFe2化合物的形成与表征(英文)

采用热力学计算和实验技术研究铝角的Al-Ca-Fe体系相图,包括液相面投影图和凝固反应。结果表明,与铝固溶体(Al)平衡的不是Al₃Fe相,而是一种组成符合化学式Al₁₀CaFe₂的三元化合物。通过包晶转变L+Al₃Fe→(Al)+Al₁₀CaFe₂(638℃,3.3%Ca和0.5%Fe,摩尔分数)发生从二元化合物到三元化合物的转变。与针状Al₃Fe相夹杂物不同,三元化合物的初晶和共晶具有致密的形貌。使用第一性原理计算和X射线衍射分析确定三元化合物Al₁₀CaFe₂的晶格结构。此外,近共晶合金Al-6%Ca-1%Fe(质量分数)在500～600℃退火后具有细晶组织,过量相的总体积分数约为25%。因此,Al-Ca-Fe体系可用于制造新的铝基复合合金。     

Ni-Ir/Al2O3负载型催化剂的制备及其用于水合肼分解制氢性能

采用一种简单的浸渍-还原工艺制备出镍-铱/氧化铝(Ni-Ir/Al₂O₃)负载型催化剂用于水合肼(N₂H₄·H₂O)催化分解制氢。该催化剂是将活性组分Ni-Ir负载于颗粒状Al₂O₃载体上制备而成，采用TEM、XRD、XPS、BET和H₂-TPD等对其结构进行表征，并结合N₂H₄·H₂O催化分解制氢实验开展了催化剂配方优化、催化反应动力学及循环耐久性研究。结果表明，粒径2～4 nm的Ni-Ir合金活性金属均匀负载于Al₂O₃载体表面，Ni₆₀Ir₄₀/Al₂O₃催化剂在293～353 K温度范围内均表现出优异的肼催化分解活性(>200 h^-1)，在该宽温域范围内的制氢选择性高达99%以上，且...     

基于同步辐射与第一性原理计算的Al/Cu钎焊界面组织与接头性能研究

界面脆性化合物对Al/Cu钎焊接头力学性能影响显著,明晰界面化合物的形成、生长行为与块体性质对调控界面组织与接头性能至关重要。本文借助同步辐射X射线成像技术对加热与冷却过程中Al/Cu钎焊界面组织演变进行动态表征,利用第一性原理计算对界面化合物的块体性质进行计算,研究了界面化合物的形成次序、模量与键合特征。结果表明,界面Al₂Cu与Al₄Cu₉化合物在冷却过程中形成,小平面枝晶状Al₂Cu化合物为初生相,从原始界面处凝固析出,且二次枝晶臂呈非对称性;与母材接触后发生扩散反应形成层状Al₄Cu₉化合物。界面化合物具有金属键与共价键的混合键合特征,Al₄Cu₉化合物具有较高的结合能、体积弹性模量、剪切模量、杨氏模量与硬度,可提高Al/Cu钎焊接头硬度,降低塑韧性。     

Al2O3/TiB2/Al复合材料的微观结构和高温力学性能

以细雾化铝粉和TiB₂颗粒为原料,通过粉末冶金和热轧制制备微米TiB₂和纳米Al₂O₃颗粒增强铝基复合材料。室温时,由于TiB₂和Al₂O₃的综合强化作用,Al₂O₃/TiB₂/Al复合材料的屈服强度和抗拉强度分别为258.7 MPa和279.3 MPa,测试温度升至350℃时,TiB₂颗粒的增强效果显著减弱,原位纳米Al₂O₃颗粒与位错的交互作用使得复合材料的屈服强度和抗拉强度达到98.2MPa和122.5 MPa。经350℃退火1000 h后,由于纳米Al₂O₃对晶界的钉扎作用抑制晶粒长大,强度和硬度未发生显著的降低。     

Li含量对高Cu铝锂合金均匀化处理的影响

通过金相显微分析(OM)、扫描电镜(SEM)、X射线衍射(XRD)、差示扫描量热法(DSC)、能谱分析(EDS)和电子探针显微分析(EPMA),研究了不同Li含量对高Cu铝锂合金铸态组织和均匀化处理的影响。结果表明：铸态高Cu铝锂合金的晶界和枝晶间有大量非平衡结晶相存在,主要为富Mg和Ag的Al-Cu相、T_B(Al₇Cu₄Li)相和θ(Al₂Cu)相;Li含量对铸锭枝晶间距和第二相种类有明显的影响,当合金中Li含量较高时,枝晶间距较小,T_B(Al₇Cu₄Li)相的占比较大;当合金中Li含量较低时,枝晶间距较大,θ(Al₂Cu)相的占比较大。θ(Al₂Cu)相占比越大,均匀化处理需要的时间越长,低Li合金、中Li合金和高Li合金适宜的均匀化制度分别为(470℃,16 h)+(500℃,40 h)、(470℃,16 h)+(500℃,24 h)和(470℃,16 h)+(500℃,8 h)。     

Al2O3f/Mg-6Al-1Nd-1Gd复合材料的显微组织及时效行为

采用维氏显微硬度计、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)等研究了Al₂O_3f/Mg-6Al-1Nd-1Gd复合材料的显微组织和时效行为。结果表明：复合材料的组织主要由α-Mg、Al₂O₃、β-Mg₁₇A1₁₂、Mg₂Si、MgO、Al₂Nd、Al₂Gd以及Al₁₁Nd₃相组成。Al₂O₃短纤维的引入加速了基体合金的时效动力学，使基体合金的时效峰值时间由32 h显著缩短至24 h。时效过程中，β-Mg₁₇Al₁₂相主要以连续析出和非连续析出两种形式析出，连续析出和非连续析出的生长呈竞争关系，随着时效时间的增加，非连续析出相逐渐长大并由晶界向晶粒内部推移，过时效阶段晶粒内部出现成片的非连续析出相。     

DD3高温合金与Ti3AlC2陶瓷的真空钎焊

通过对比试验优选出了合适钎料,并进行了后续钎焊试验.在钎焊温度800~900℃,保温时间为10 min的条件下,采用Ag-Cu-Ti钎料实现了DD3镍基高温合金与Ti₃AlC₂陶瓷的真空钎焊连接.利用扫描电镜、能谱仪、XRD等对接头的界面结构进行了分析.结果表明,接头的典型界面结构为DD3/AlNi/Al₃(Ni,Cu)₅+Al(Ni,Cu)+Ag_ss/(Al,Ti)₃(Ni,Cu)₅/Al₄Cu₉+AlNi₂Ti+Ag_ss/TiAg/Ti₃AlC₂.接头的力学性能测试表明,在钎焊温度为850℃,保温时间为10 min的条件下,接头的最高抗剪强度可达135.9 MPa,断裂发生在靠近钎缝的Ti₃AlC₂陶瓷侧.降低和提高钎焊温度对接头界面组织影响不大,但接头强度有一定程度下降.     

The Corrosion of Cu–Al Binary Alloys in H2/H2S/H2O Atmospheres at 400–900°C

The corrosion behavior of pure Cu and of three Cu–Al alloys containing 1, 5, and 10 wt.% Al was studied at 400–900°C in a H₂/H₂S/H₂O gas mixture. Both Cu–1Al and Cu–5Al alloys had the single-phase structure of α-Cu, while Cu–10Al was the intermetallic compound Cu₃Al. In general, the corrosion behavior of all the alloys followed the parabolic rate law, and the corrosion rate constants generally increased with increasing temperature but decreased with increasing Al content. The scale formed on pure Cu was an exclusive single layer of Cu₂S, while the scales formed on Cu–Al alloys were heterophasic and duplex, consisting of an outer layer of Cu₂S and an inner layer of Cu₂S and CuAlS₂. X-ray diffraction results showed no evidence of oxides and the amount of CuAlS₂ increased with increasing Al content. The formation of Cu₂S and CuAlS₂ on higher Al-content alloys resulted in a subsurface phase transformation from α-Cu (for Cu–5Al) or from Cu₃Al (for Cu–10Al) to Cu₃Al + Cu₉Al₄. The formation of CuAlS₂ in the inner layer of Cu–Al alloys was responsible for the reduction of corrosion rates, as compared to those of pure Cu.     

Structure and denitration performance of carbon-based catalysts prepared from Cu–BTC precursor

Using Cu–BTC prepared by hydrothermal method as precursor, carbon-based catalysts were obtained as model materials for low-temperature DeNO_x. These catalysts were characterized by X-ray diffractometry (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The results showed that all carbon-based catalysts held the octahedron shape of Cu–BTC in most parts, and they mainly consisted of face-centered cubic copper. CuO_x/C exhibited excellent catalytic activity, and such catalytic activity was further improved with the introduction of Ag. The catalyst with a Cu to Ag mole ratio of 6:1 and an activated temperature of 600 °C showed the best catalytic performance, and its catalytic denitration rate reached 100% at a temperature as low as 235 °C. During the catalytic reaction process, Cu⁺ mainly played a catalytic role.     

Isothermal Section of the Al-Mn-Dy System at 500 °C

Phase relationships in the Al-Mn-Dy ternary system at 500 °C have been investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and electron probe microanalysis. From the experimental results it was concluded that the isothermal section consists of 16 single-phase regions, 26 two-phase regions and 12 three-phase regions. Two extensive solid solutions, (Al _x Mn_1?x )₁₂Dy and (Al_1?x Mn _x )₂Dy, were observed. The solid solution (Al _x Mn_1?x )₁₂Dy forms by Al replacing Mn in Mn₁₂Dy, while the continuous solid solution (Al_1?x Mn _x )₂Dy forms by Mn and Al mutually substituting in Al₂Dy and Mn₂Dy, respectively. The maximum solid solubility of Al in Mn₁₂Dy is 79.3 at.%.     

Sulphidation/oxidation behaviour of TiAlCr and Al2Au coated Ti45Al8Nb alloy at 750 °C

In this paper, we present the sulphidation/oxidation behaviour of a Ti45Al8Nb (at%) alloy coated with different protective surface films. Two intermetallic coatings are considered; TiAlCr and Al₂Au deposited by physical vapour deposition. The coated alloy was subjected to a H₂/H₂S/H₂O yielding pS₂ - 10⁻¹ Pa and pO₂ - 10⁻¹⁸ Pa potentials at 750 °C for up to 1000 h. The corrosion kinetics were determined by means of discontinuous gravimetry and the as-received and exposed samples were characterised using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). The materials showed the development of a multilayered structure. In the case of the TiAlCr coated Ti45Al8Nb - base alloy, Al₂O₃, TiO₂ and Cr₂S₃ developed. For the Al₂Au coated Ti45Al8Nb samples an Al₂O₃ scale containing TiO₂ nodules was observed at the surface.     

Thermodynamic calculation of high zinc-containing Al-Zn-Mg-Cu alloy

Phase fraction and solidification path of high Zn-containing Al-Zn-Mg-Cu series aluminum alloy were calculated by calculation of phase diagram (CALPHAD) method. Microstructure and phases of Al-9.2Zn-1.7Mg-2.3Cu alloy were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The calculation results show that η(MgZn₂) phase is influenced by Zn and Mg. Mass fractions of η(MgZn₂) in Al-xZn-1.7Mg-2.3Cu are 10.0%, 9.8% and 9.2% for x=9.6, 9.4, 8.8 (mass fraction, %), respectively. The intervals of Mg composition were achieved for θ(Al₂Cu)+η(MgZn₂), S(Al₂CuMg)+η(MgZn₂) and θ(Al₂Cu)+S(Al₂CuMg)+η(MgZn₂) phase regions. Al₃Zr, α(Al), Al₁₃Fe₄, η(MgZn₂), α-AlFeSi, Al₇Cu₂Fe, θ(Al₂Cu), Al₅Cu₂Mg₈Si₆ precipitate in sequence by no-equilibrium calculation. The SEM and XRD analyses reveal that α(Al), η(MgZn₂), Mg(Al,Cu,Zn)₂, θ(Al₂Cu) and Al₇Cu₂Fe phases are discovered in Al-9.2Zn-1.7Mg-2.3Cu alloy. The thermodynamic calculation can be used to predict the major phases present in experiment.     

The Fe–Ni–Al phase diagram in the Al-rich (>50 at.% Al) corner

The ternary Fe–Ni–Al phase diagram between 50 and 100 at.% Al was investigated by a combination of powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe microanalysis (EPMA). Ternary phase equilibria and accurate phase compositions of the respective equilibrium phases were determined within the isothermal section at 850 °C. The crystal structure of τ1 (Fe_4−xNi_xAl₁₀) and τ2 (Fe_2−xNi_xAl₉) was determined by means of single crystal X-ray diffraction. The decagonal quasi-crystalline phase q (Fe_4.9Ni_23.4Al_71.7) was found to be stable between 850 °C and 930 °C. All experimental data were combined to yield a ternary reaction scheme (Scheil diagram) involving 10 ternary invariant reactions in the investigated composition range, and a liquidus surface projection was constructed based on DTA results.     

Mechanism and kinetics of iron extraction from high silica boehmite–kaolinite bauxite by hydrochloric acid leaching

The chemical and mineral compositions of bauxite recovered from the Severoonezhsk Bauxite Mine (Arkhangelsk region, Russia) were studied by XRD, ICP-OES, TG/DSC, SEM, TEM, and Mössbauer spectroscopy. The iron-containing minerals of the bauxites were found to comprise alumogoethite (α-Fe_1–xAl_xOOH), alumohematite (α-(Fe_1–xAl_x)₂O₃), alumoakaganeite (β-Fe_1–xAl_xO(OH,Cl)), and chromite (FeCr₂O₄). The efficiency of Fe extraction from the bauxite by HCl leaching was 82.5% at 100 °C, HCl concentration of 10%, solid/liquid ratio of 1:10, and the process duration of 60 min, with aluminum loss from the bauxites below 4.5% of the total Al contents in the bauxite. Analysis of the kinetics of the iron leaching process proved diffusion to be the limiting stage of the process at 90–100 °C. Bauxite residue after leaching presented traces of α-Fe_1–xAl_xOOH and β-Fe_1–xAl_xO(OH,Cl), and most of the iron content was in the FeCr₂O₄. In bauxite residue after HCl leaching, in addition to iron oxide, the contents of chromium and calcium oxides significantly decreased. The iron chloride liquor after leaching contained the rare earth elements (REE) of 6.8 mg/L Sc, 4.1 mg/L Ce and 2.3 mg/L Ga.     

Influence of oxygen on the crystallization behavior of Zr65Cu27.5Al7.5 and Zr66.7Cu33.3 metallic glasses

The influence of oxygen on the crystallization behavior of Zr_65−xCu_27.5Al_7.5O_x (x=0.14, 0.43 and 0.82) and Zr_66.7−xCu_33.3O_x (x=0.14 and 0.82) metallic glasses has been studied. The supercooled liquid regime (ΔT_x) decreases with increase in oxygen content for the Zr–Cu–Al alloy, while it increases for the Zr–Cu metallic glass. In the case of the Zr–Cu metallic glass, the crystallization product (Zr₂Cu) is not influenced by the oxygen content, while in Zr–Cu–Al alloys the oxygen level has a strong influence on the crystallization sequence. At low oxygen level (x=0.14), the ternary glass crystallizes polymorphously to Zr₂(Cu,Al). At higher oxygen content, the ternary amorphous alloy crystallizes in two stages by primary crystallization into an icosahedral phase and subsequently to the stable Zr₂(Cu,Al) phase. Three-dimensional atom probe results have shown that the composition of the icosahedral and amorphous phases is close to Zr₇₅Cu₁₅Al₅O₅ and Zr₆₂Cu₂₄Al₁₄, respectively.     

Effects of heat treatment on phase contents and mechanical properties of infiltrated B4C/2024Al composites

The B₄C/2024Al composites were successfully produced by pressureless infiltration method, and the effects of heat treatment on phase content and mechanical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical properties testing. The results show that phases of B₄C/2024Al composites include B₄C, Al, Al₃BC, AlB₂ and Al₂Cu. The phase species remain unchanged; however, the phase content of the composites changes significantly after heat treatment at the temperature of 660, 700, 800 or 900 °C for 12, 24 or 36 h. It is found that the heat treatment results in not only considerable enhancement in hardness, but also reduction in bending strength of the composites. Heat treatment at 800 °C for 36 h does best to hardness of the composites, while at 700 °C for 36 h it is the most beneficial to their comprehensive mechanical properties.     

Phases and microstructures of high Zn-containing Al–Zn–Mg–Cu alloys

Phases and microstructures of three high Zncontaining Al–Zn–Mg–Cu alloys were investigated by means of thermodynamic calculation method, optica microscopy(OM), scanning electron microscopy(SEM)energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), and differential scanning calorimetry(DSC) analysis. The results indicate that similar dendritic network morphologies are found in these three Al–Zn–Mg–Cu alloys. The as-cast 7056 aluminum alloy consists of aluminum solid solution, coarse Al/Mg(Cu, Zn, Al)_2 eutectic phases, and fine intermetallic compounds g(MgZn_2). Both of as-cast 7095 and 7136 aluminum alloys involve a(Al)eutectic Al/Mg(Cu, Zn, Al)_2, intermetallic g(MgZn_2), and h(Al_2Cu). During homogenization at 450 °C, fine g(MgZn_2) can dissolve into matrix absolutely. After homogenization at 450 °C for 24 h, Mg(Cu, Zn, Al)_2 phase in 7136 alloy transforms into S(Al_2Cu Mg) while no change is found in 7056 and 7095 alloys. The thermodynamic calculation can be used to predict the phases in high Zncontaining Al–Zn–Mg–Cu alloys.