Effects of Sn additions on microstructure and corrosion resistance of heat-treated Ti–Cu–Sn titanium alloys

The microstructure and corrosion properties of Ti7CuxSn (x?=?0–5?wt-%) alloys after solution treatment have been investigated. The alloys were solution-treated (ST) at 1000°C for 2?h, followed by quenching in water to room temperature. It was found that the microstructure of the ST Ti7Cu alloy had only a martensite structure, and that addition of Sn could refine the microstructure of Ti7CuxSn alloy. Notably, the pseudo dendritic α-Ti phase was formed in ST Ti7Cu5Sn alloys. Potentiodynamic polarisation curves and electrochemical impedance spectroscopy data demonstrated that adding Sn improved the electrochemical corrosion behaviour of the Ti7CuxSn alloy.     

稀土氧化镧掺杂钼合金的强化机制研究

使用粉末冶金工艺制备了不同体积分数稀七氧化镧颗粒掺杂的钼合金。观察了该合金的显微组织并测试了其力学性能。结果表明，稀士氧化镧掺杂钼合金由于其细小的氧化镧颗粒和细小的晶粒的作用而具有较高的屈服强度。对稀士氧化镧掺杂钼合金强化机制的分析结果表明，钼合金的屈服强度主要来源于三个部分：变形前基体强度、细小稀士氧化镧颗粒贡献的强度和细小钼合金晶粒贡献的强度，并给出了稀土氧化镧掺杂钼合金屈服强度与稀土氧化镧颗粒尺寸、体积分数以及晶粒尺寸之间的定量解析关系。     

A diffusional analysis of the oxidation of binary multiphase alloys

A nonsteady-state diffusional analysis has been applied to the oxidation of binary multiphase alloys. In addition to the solubility of the solute element in the continuous solid-solution phase, the volume fraction and the size of the second-phase particles have been found to be crucial for the exclusive formation of the solute oxide. By solving the diffusion equations, the oxidation behavior of a multiphase alloy has been quantitatively related to a microstructure parameter, P _L ,which is a function of both the volume fraction and shape of the second phase. Moreover, the effectiveness of alloying for alloys with differently shaped second-phase particles on the oxidation of multiphase alloys has been discussed.     

The Air Oxidation of Two-Phase Fe-Cu Alloys at 600-800°C

The air oxidation of three Fe-Cu alloyscontaining 25, 50, and 75 wt.% Cu has been studied at600-800°C. The oxidation followed the parabolic lawonly approximately with rates lower than those of thepure constituent metals. The scales were alwayscomposed of an inner layer containing a mixture ofcopper metal and iron oxide and of an outer oxide layerwhose composition depended on the copper content of the alloy. For the two alloys richer in ironthe external layer was composed mostly of iron oxideswith some copper-rich particles which oxidized only inthe external-scale zone. For the alloy richest in copper the external layer contained a complexmixture of iron oxides, copper particles and doubleFe-Cu oxides surmounted by an outermost copper-oxidelayer. No significant iron depletion was observed in the alloys beneath the region of internaloxidation. The peculiar scale microstructure observedfor these alloys is considered mainly as a consequenceof their two-phase microstructure and of the limited solubilities of the two components in oneanother.     

The oxidation of a directionally solidified cobalt-tungsten eutectic alloy

A study of the oxidation of directionally solidified Co-W alloys were performed at 750, 900, and 1050°C. The study involved a comparison of the oxidation behavior of directionally solidified and as-cast alloys along with the oxidation behavior of the pure components. The study incorporated both thermogravimetric kinetic measurements and morphological studies of the oxides as a function of both temperature and time. Differences were noticed in both the oxidation rate and the oxide morphology and were attributed to differences in alloy microstructure. The directionally solidified Co-W alloy was found to be more spall resistant but also oxidized more rapidly than the conventionally as-cast alloy. Both alloys were more oxidation resistant than the pure components.     

Optimization of manufacturing process for highly corrosion resistant Zr alloys

The influence of the manufacturing process on the microstructure and corrosion characteristics of newly developed Zr alloys, Zr-lNb-Cu and Zr-0.2Nb-1.3Sn-0.4Fe-0.2Cr-Cu, was investigated. An autoclave corro-sion test at 400°C steam was carried out for specimens prepared by various manufacturing processes. SEM and TEM studies were also conducted to investigate the microstructure of heat-treated samples and to observe the oxide/metal interface of corroded specimens. The microstructure and corrosion resistance of the alloys were found to be significantly affected by the manufacturing process conditions. For good corrosion resistance, sufficient annealing should be introduced to form β-Nb in the Zr-lNb-Cu alloy while only limited annealing should be conducted to obtain small precipitates in the Zr-0.2Nb-1.3Sn-Fe-Cr-Cu alloy.     

Te-Ni-Cr合金在3.5%Nacl溶液中的腐蚀行为研究

利用粉末冶金技术制备新型Te-Ni-Cr合金材料,在人造海水中进行全浸腐蚀试验,通过金相组织观察、扫描电镜对表面腐蚀形貌的观察、表面EDS及XRD对腐蚀产物的分析,研究了Te-Ni-Cr合金的耐蚀性能。结果表明,碲元素的加入改变了试祥的显微结构,形成黑灰色突起的骨骼状组织,对整个合金的表面起支撑保护作用;经XRD分析确定腐蚀产物为Ni_2O_3和铁的氧化物,计算腐蚀速率得到,Te-Ni-Cr合金的耐蚀性较未加碲的有所提高。     

Ti-Cr合金的非等温氧化及着火预测(英文)

采用热重分析、XRD和SEM等方法研究Ti-Cr合金(0≤w(Cr)≤25%)从室温至1723K的非等温氧化行为及氧化膜的微观结构,探讨Cr元素对Ti-Cr合金抗氧化能力的影响机制。结果表明:当Cr含量小于某一临界值wC时,随着Cr含量的增加合金的抗氧化能力降低;当Cr含量高于wC时,随着Cr含量的增加合金的抗氧化能力提高;当温度高到1000K时,Ti-Cr合金的氧化仍符合抛物线规律,且主要发生钛的氧化;Ti-Cr合金氧化后基体中存在氧扩散层,氧化膜主要为金红石型TiO2,内层氧化膜出现富Cr现象,Cr氧化物的析出提高了Ti-Cr合金的抗氧化能力。金属和合金的着火是一个快速非等温氧化的过程,预测了Ti-Cr合金着火阶段的氧化机制。     

Influences of Ti substitution on the structure and electrochemical properties of Mg1-xTixNi（x=0,0.1, 0.2, and 0.3） hydrogen storage alloys

MgNi-based hydrogen storage alloys Mg_1−x Ti _x Ni (x = 0, 0.1, 0.2, and 0.3) were prepared by means of mechanical alloying. Mg in the alloy was partially substituted by Ti to improve the cycle stability of the alloys. The effects of the substitution of Ti for Mg on the microstructure and electrochemical performances of the alloys were investigated in detail. The results indicate that the substitution of Ti for Mg obviously decreases the discharge capacity, but it significantly improves their cycle stabilities. The microstructure of the alloys analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) shows that the alloys have a dominatingly amorphous structure. The substitution of Ti for Mg helps to improve the anti-oxidation/corrosion ability of the MgNi alloy but demolishes the electrochemical kinetics of hydrogenation/dehydrogenation. The Mg_0.9Ti_0.1Ni alloy electrode milled for 80 h exhibits the best integrative capability, which has the maximal discharge capacity of 331.66 mAh/g and the C ₃₀/C _max of 63.65%.     

Oxidation resistance of aluminum-coated Fe-20Cr alloys containing rare earths or yttrium

Aluminum-coated Fe-20Cr-(rare earth or yttrium) alloy foils were developed with oxidation resistance equivalent or superior to Fe-20Cr-5Al-(rare earth or yttrium) alloy foils. The coated foils were made by dipping Fe-20Cr sheet into a salt-covered aluminum bath and then rolling the sheet to foil. Oxidation resistance of the coated foil was enhanced by adding rare earths or yttrium to the Fe-20Cr substrate alloys to insure oxide adherence. Test results indicate that only sufficient addition to tie up sulfur as a stable sulfide is needed in the Fe-20Cr alloy. Aluminum-coated foils show lower oxide growth rates than similar Fe-Cr-Al alloys, most likely the result of fewer impurities (particularly Fe) is the coated foils' growing oxide scale.     

Effect of rare earth on the microstructure and mechanical properties of as-cast Cu-30Ni alloy

Cu-30Ni-xRE (x = 0–0.213) alloys were prepared by a metal mould casting method. The effect of RE on the microstructure and mechanical properties of the alloys was investigated using optical microscope, scanning electronic microscope with energy-dispersive spectrometer, X-ray diffraction, and mechanical test. The results show that RE has obvious effect on refining dendrite structure and grain size, as well as on purifying the melting of Cu-30Ni alloy. With the increase of RE content, the ultimate tensile strength, yield strength, and elongation increase at first and then decrease after adding RE more than 0.095 wt.%. Cu-30Ni-0.095RE alloy possesses preferable mechanical properties, i.e., the ultimate tensile strength, yield strength, and elongation are 308 MPa, 125 MPa, and 51.2%, respectively. The microstructure and mechanical properties are worsened with increasing RE content more than 0.095 wt.%. The improvement of mechanical properties of Cu-30Ni-0.095RE alloy is attributed to RE refining microstructure and purifying the matrix.     

Oxidation Behavior of Ni–Cr–Fe-Based Alloys: Effect of Alloy Microstructure and Silicon Content

The oxidation behavior of Ni–Cr–Fe-based alloys in a low oxygen partial pressure atmosphere (H₂–H₂O) was investigated in terms of the effect of alloy microstructure and their silicon content. It was found that the formation and growth kinetics of the oxide scale are rather sensitive to the alloy microstructure and their corresponding Si contents. Oxide ridges were found to form in areas with eutectic structure, while a thin and homogeneous oxide scale formed on austenite matrix. The thicknesses of the oxide ridges and the oxide layer on the austenite matrix were dependent of their corresponding Si contents. The austenite/carbide phase boundaries in eutectic structure can offer fast diffusion paths for metal outward diffusion, which leads to the formation of ridge-like oxide features. The continuous SiO₂ sub-layer formed at the oxide scale/metal interface on the austenitic matrix acted as an effective diffusion barrier to metal outward diffusion, resulting in rather thin and uniform oxide scales.     

Mo-Zr合金烧结致密化行为及组织与性能研究

在含有不同氟离子浓度的硅酸钠电解液体系中,采用恒压微弧氧化技术对AZ31镁合金进行表面处理,通过XRD、SEM、EDS等研究镁合金表面微弧氧化膜层形貌和相结构特征,探讨氟离子对膜层形成的影响规律.研究结果表明:随着氟离子浓度的增加,膜层微孔数量逐渐减少,微孔孔径逐渐变大且分布均匀,但氟离子浓度过高时,膜层缺陷增多,出现微裂纹和局部孔径较大的微孔;微弧氧化膜层主要由MgAl2O4和MgSiO3组成,其含量随着氟离子浓度的变化而变化,当氟离子浓度范围为2～4 g/L时微弧氧化膜中MgAl2O4和MgSiO3的含量最高;动电位极化曲线表明微弧氧化膜的耐腐蚀性能也随之呈先增后减的趋势.     

Effect of alloy grain size and silicon content on the oxidation of austenitic Fe-Cr-Ni-Mn-Si alloys in pure O2

Austenitic Fe-18Cr-20Ni-1.5Mn alloys containing 0, 0.6, and 1.5 wt.% Si were produced both by conventional and rapid solidification processing. The isothermal and cyclic oxidation resistance of the alloys were studied at 900°C in pure O₂ to elucidate the role of alloy microstructure and Si content on oxidation properties. The conventionally-processed, large-grained alloy that contained no silicon formed Fe-rich nodules during oxidation. The nodule formation was effectively eliminated by either reducing the alloy grain size by rapid solidification or by adding Si to the alloy. The lowest weight gains were achieved when a continuous silica layer formed between the alloy and the external chromia scale. The formation of the continuous silica layer required a ombination of fine alloy grain size and high Si content. The presence of S in the alloy was found to be detrimental to oxide scale adherence when the silica layer was continuous.     

显微组织对Cu—Cr—Ni合金高温氧化行为的影响

研究了两种单／双相Cu-Cr-Ni合金的高温氧化行为。结果表明,合金氧化动力学偏离抛物线规律,其瞬时抛物线速率常数随时间延长而降低。两种合金表面氧化膜的结构差别较大,单相合金表面形成－连续的Cr2O3层,双相合金表面氧化膜外层是一边疆的CuO层,Ni和Cr的氧化发生在合金内部,这种合金与氧化物共存的混合内氧化与经典的内氧化明显不同,氧化层最里面形成了一连续的CrO3膜,抑制了合金的进一步氧化。     

Oxidation of ruthenium aluminide-based alloys: The role of microstructure and platinum additions

The cyclic oxidation behavior of six RuAl-based alloys was studied in air over the temperature range of 1000–1300 °C. Oxidation kinetics were influenced by microstructure as well as the addition of platinum. Single phase RuAl-based alloys formed a layered oxide structure during oxidation. The presence of the δ-Ru-rich eutectic along grain boundaries strongly accelerated the oxidation process. A single phase Pt-containing RuAl-based alloy exhibited the highest oxidation resistance.     

Structural and Mössbauer spectroscopic investigation of Fe substituted Ti–Ni shape memory alloys

In the present investigation the effect of Fe substitution in Ti₅₁Ni₄₉ alloy has been studied. The alloys were synthesized through radio frequency induction melting. The alloy was characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy and positron annihilation techniques. It was found that the Fe substitution stabilized the TiNi type cubic (a = 2.998 Å) phase. The microstructure and presence of the oxide phase in Ti₅₁Ni₄₅Fe₄ alloy have been investigated by scanning electron microscopy. The positron annihilation measurements indicated a similar bulk electron density in both the as-cast and annealed (1000 °C for 30 h) alloys, typically like that of bulk Ti. Mössbauer spectroscopy studies of as-cast and annealed iron substituted samples showed regions in the samples where nuclear Zeeman splitting of Fe levels occurred and an oxide phase was found to be present in as cast Ti₅₁Ni₄₅Fe₄ alloy, while annealed sample indicated the presence of bcc iron phase.     

Ag-Cu-Al-Y合金在Na2S溶液中的腐蚀行为研究

采用腐蚀失重法研究了Ag-Cu-Al-Y合金在Na2S溶液中的腐蚀动力学行为,利用金相(OM)、扫描电子显微镜(SEM)和能谱(EDS)等手段分析了合金腐蚀前后显微组织,探讨了Ag-Cu-Al-Y合金在Na2S溶液中的腐蚀机理。结果表明,添加稀土Y能明显改善Ag-Cu-Al的抗硫化腐蚀性能,其中添加0.03at%Y的银合金具有最小的硫化腐蚀速率。在Ag-Cu-Al-Y合金的硫化腐蚀过程中,腐蚀优先发生在晶界处,腐蚀过程首先形成保护性的致密氧化物层(Y2O3和Al2O3),阻碍氧、硫离子进一步扩散;随着氧化层的逐步剥落,氧、硫离子迅速扩散进入合金内部,并优先与Cu反应形成Cu2S。腐蚀产物内层组织主要为致密氧化物层,外层疏松组织为氧化物和硫化物共存组织。     

Effect of Minor Er on the Microstructure and Properties of Al-6.0Mg-0.4Mn-0.1Cr-0.1Zr Alloys

As-cast Al-6.0Mg-0.4Mn-0.1Cr-0.1Zr alloys containing different additions of Er were prepared. Then, the specimens were carried out homogenization heat treatment, hot rolling, cold rolling, and annealing. The effects of minor Er on the microstructure and properties of Al-6.0Mg-0.4Mn-0.1Cr-0.1Zr alloy were investigated. Results show that addition of Er can refine the microstructure and improve the mechanical properties of the alloys. As for the annealed alloys, the addition of 0.33%Er can increase the tensile strength by 29 MPa. Strength increment is mainly attributed to refinement and the precipitation of Al₃Er and Al₃(Er, Zr). Additionally, the minor Er can improve the corrosion resistance of the alloys, which can be attributed to the compact composite oxide film of Er-O and Al-O, purification, and modification.     

FeCrMnAlCux高熵合金在0.5 M H2SO4溶液中耐腐蚀性能的研究

本文采用真空电弧熔炼技术制备出FeCrMnAlCux(x=0, 0.5, 1.0, 1.5, 2.0)高熵合金,通过XRD、SEM、EDS对合金的相结构及腐蚀前后的微观组织进行表征,利用动电位极化曲线、EIS、XPS以及浸泡实验对合金在0.5M H2SO4溶液中的腐蚀性能进行分析。研究结果表明：Cu元素的加入促进了合金中FCC相的形成,使合金由单一BCC结构转变为BCC+FCC双相混合结构。五种成分的高熵合金具有典型的枝晶形貌,随着Cu含量的增加,晶粒逐渐细化,组织逐渐均匀。FeCrMnAlCu1.5高熵合金的腐蚀电位最高(-0.363 V),腐蚀电流密度最小(2.148×10-5 A/cm2),合金的耐蚀性随着Cu含量的增加先提高后下降,当x=2.0时,腐蚀电位减小到-0.394 V,电流密度增大到2.865×10-4 A/cm2,其耐蚀性能仍优于未添加Cu元素的合金。腐蚀后合金截面处形成了复合氧化物保护膜,有效降低了合金在0.5 M H2SO4溶液中的腐蚀速率。