热处理对AB_3型无Co贮氢合金电化学性能的研究

用真空熔炼法制备了多种贮氢合金原样,分别经不同温度、时间热处理和保护气氛下球磨处理.改性前后样品晶体结构用SEM和XRD测试进行结构表征,结果表明合金为LaNi_5和LaMg_2Ni_9晶相的复合相,经过热处理的合金颗粒粒径变小针刺变少、分布也相对更均匀.采用LANDAN进行电化学相关测试(电流密度为150mA/g),表明经过热处理使得晶体结构优化,放电容量有显著增加,且经由Al替代Ni的合金容量达到353.7mAh/g,循环50周容量保持率为76.7%,循环100周容量保持率为62.7%,表现出更好的循环稳定性.实验结果表明,无Co替代贮氢合金经热处理后电化学性能有显著提高,有望降低合金材料成本的同时提高材料的环境友好性.     

热处理对真空热压烧结NiCrCoTiV高熵合金组织结构及耐腐蚀性能的影响

采用真空热压烧结技术制备了NiCrCoTiV高熵合金,并分别在500℃、600℃和700℃下对高熵合金进行18h保温热处理。采用X射线衍射仪、扫描电子显微镜、电化学测试系统研究了不同热处理温度对高熵合金物相结构、微观组织及耐腐蚀性能的影响。结果表明,高熵合金的物相组成在不同温度热处理后均未发生明显改变,表现出良好的热稳定性。热处理后,高熵合金晶粒细化,析出相减少;热处理温度越高,晶粒细化效果越好。相比于未热处理的试样,热处理后试样的耐腐蚀性能明显提高,并且随热处理温度升高,耐腐蚀性能呈上升趋势。     

热处理对Al-Sn-Bi-Pb-In阳极材料电化学及腐蚀性能的影响

热处理能提高铝合金的耐蚀性,但高温固溶会降低其电化学活性,低温回火会影响其耐蚀性,目前结合二者优势的报道较少.熔炼制备了Al-Sn-Bi-Pb-In合金,采用电化学方法和化学浸泡失重法研究了高温固溶、低温回火热处理对其电化学性能及耐蚀性能的影响;采用扫描电镜观察了不同热处理状态铝合金腐蚀后的表面形貌.结果表明:铝合金阳极高温固溶处理后电化学活性降低,耐蚀性提高;再作低温回火后铝合金阳极电化学性能提高,耐蚀性稍有降低;最佳热处理为500℃固溶6h之后再在150℃下回火8h.     

氧流量和热处理温度对锡酸锌薄膜结构的影响

本文采用锌锡质量比为52:48的Zn-Sn合金靶,利用中频交流反应磁控溅射方法,制备了锡酸锌(Zn2SnO4)晶体薄膜.考察比较了氧流量和热处理温度对锌锡合金氧化物薄膜晶体结构的影响,确定了制备晶态Zn2SnO4薄膜的合适氧流量和热处理温度.通过XRD分析了薄膜的晶体结构和组成.结果表明:室温条件下制备的沉积态锌锡合金氧化物薄膜,均呈非晶态结构;在基底温度为室温,氧流量达到60sccm以上条件下制备锌锡氧化物薄膜进行热处理,热处理温度在高于550℃,薄膜中开始出现Zn2SnO4晶体结构,随着热处理温度升高,薄膜中晶态结构大量增加;在氧流量(60～70) sccm、热处理温度650 ℃条件下,形成完全结晶态Zn2SnO4薄膜.     

真空热处理对石墨涂覆铀表面氧化和电化学腐蚀的影响

为了探讨石墨涂层铀表面经真空热处理后对铀抗蚀性能的影响,通过增重法和电化学方法研究了处理样在100℃和150℃、含有一定量O2和H2O(g)气氛中的抗氧化腐蚀性和50μg/g Cl-溶液中的抗化学介质腐蚀性.抗氧化腐蚀试验表明,当热处理时间(5 h)不变时,在600℃处理要优于在500℃处理.电化学试验表明,处理样品的抗蚀性能与热处理时间(2.5～10.0 h)和温度(500～650℃)有关,且在600℃处理5 h的样品的抗化学介质腐蚀性能最佳.真空热处理可以提高石墨涂层铀表面的抗蚀性能.     

热处理对化学沉积Ni-Fe-P合金磁性能的影响

采用差示扫描量热、X射线衍射和扫描电镜研究了化学沉积Ni-Fe-P合金的晶化行为和表面形貌.结果表明,镀态合金呈非晶结构,367.6℃下热处理出现亚稳态Ni5P2(P3)和Fe-Ni(Im3m),499.2℃下热处理进一步晶化为稳定的Ni3P(I-4)和FeNi3(Pm3m).镀层经过500℃热处理生成许多粒径为30～50nm的纳米颗粒,而经过600℃热处理后颗粒变大.研究了热处理对镀层显微硬度和磁性能的影响.发现该镀层在镀态时和经过200℃热处理后几乎没有磁性,随着退火处理温度的升高,镀层的显微硬度和磁性能不断提高;500℃达到最高,随后这些性能随着退火温度的升高而降低.     

加工工艺对Ti600合金棒材性能的影响

通过对精锻、自由锻、旋锻及热轧4种加工方式获得的Ti600合金棒材在3种不同的热处理制度下进行处理,再测试室温拉伸性能及蠕变性能,研究不同加工工艺对Ti600合金棒材性能的影响.研究结果表明,在同一种热处理制度下,加工工艺对材料的室温拉伸性能及蠕变性能并无太大影响,但是4种工艺加工的棒材在1 060℃,1 h,AC+650℃,8 h,AC都具有较低的室温塑性,而在1 005℃,1 h,AC+650℃,8 h,AC虽具有好的室温塑性但抗蠕变性能较差.只有经过1 020℃,1 h,AC+650℃,8 h,AC处理,才能使其室温性能与蠕变性能获得良好的匹配.     

热处理对AB5型快淬态储氢合金组组结构及电化学性能的影响

为了研究热处理对AB5型快淬态储氢合金的组织结构及电化学性能的影响,在773K和973K分别对三种成分的快淬态储氢合金La1-xAx(Ni,Co,Sn)5进行了热处理,利用XRD与TEM技术分析了合金热处理前后的组织结构,利用充放电测试装置,研究了合金热处理前后的电化学性能.研究结果表明:热处理使合金内部晶格应力得以释放,恢复了扭曲的晶胞形状,使合金可以吸收更多的氢;热处理使晶粒得以细化,晶界比例相应增加,抗粉化能力增强.经过热处理后合金的容量及循环寿命均有所提高.     

热处理温度对非晶合金耐蚀性能的影响

目的 在非晶合金过冷液相区范围内研究热处理温度对非晶合金耐蚀性能的影响。方法 采用差示扫描量热法来表征非晶合金,并作出非晶合金的差热曲线,以此来确定非晶合金的玻璃化转变温度Tg和晶化温度Tx,进而求出其过冷液相区范围,以此来确定热处理退火温度范围。随后在过冷液相区范围内均匀选取3个不同温度点对非晶合金进行热处理,最后在质量分数为3.5%的NaCl溶液中对非晶合金进行电化学测试,并与未处理样品进行比较,进而发现其耐蚀性规律。结果 经过不同的热处理后,非晶合金在质量分数为3.5%的NaCl溶液中的电化学腐蚀结果相差较多。结论 在保温时间和冷却方式不变时,随着热处理温度的增加,非晶合金的耐蚀性呈下降趋势。退火温度为540 ℃时,非晶合金的耐蚀性能最佳。     

热处理对Ti-35V-15Cr-0.15Si-0.05C合金热稳定性能的影响

通过对Ti-35V-15Cr-0.15Si-0.05C合金轧制环件取样进行热处理和热稳定性能实验,研究了850℃和950℃固溶处理和950℃固溶后在600℃和700℃实效后的热稳定性能和微观组织。结果表明:合金仅经过固溶处理α相析出不明显,而经过固溶加时效处理后α相在晶界和晶内大量析出,在热稳定性能测试时,经过540℃100h热暴露后,α相进一步析出。合金α相是影响合金拉伸性能的主要因素,在晶界析出的连续α相导致合金塑性急剧下降;通过850℃固溶热处理能够获得较好的室温拉伸和热稳定性能。     

The effect of H2-anneal on the adhesion of Al2O3 scales on a Fe3Al-based alloy

Abstract

The cyclic (1,100°C, air) and isothermal (1,000°C, O₂) oxidation behavior of a Fe-28Al-5Cr (at%) alloy, with and without a prior H₂-anneal heat treatment at 1,200°C for 100 h, was studied. Changes in interfacial chemistry were evaluated using Scanning Auger Microscopy after removal of the oxide film in ultra high vacuum. This was achieved by making a scratch on the specimen surface, which caused spallation of the film at various locations along the scratch. The scale thickness and the temperature drop at which spallation took place during cooling were utilized to semi-quantitatively compare the adherence of the scales. Porosity at the scale–alloy interface and the scale microstructure were determined from scanning electron microscope observations. It was found that H₂-anneal greatly improved scale adhesion and resulted in a pore-free and sulfur-free interface. The effects were similar to that of a 0.1 at% Zr-containing alloy, except that the improvement in scale adhesion was not as great as that from Zr doping. This implies that oxide/alloy interfaces are not intrinsically strong and the effect of reactive elements, such as Zr, is more than preventing impurity from segregating to the interface. Results are also compared with the effect of H₂-anneal on other model alloys, such as NiCrAl, FeCrAl and NiAl, and on single crystal superalloys.     

Experimental and Theoretical Evaluation of Rutin as Eco-Friendly Corrosion Inhibitor for Aluminum 6063 Alloy in Acidic Medium

The corrosion inhibition characteristics of rutin a natural flavonoid glycoside has been studied as an eco-friendly green inhibitor for corrosion control of aluminum alloy AA6063 in 0.5 M HCl medium at a temperature range of 30–60 °C by weight loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. The inhibition efficiency increased with the increase in concentration of the inhibitor and also with increase in temperature. The surface morphologies of the polished, corroded and inhibited surfaces were scanned using the scanning electron microscope images. The activation parameters like energy of activation, enthalpy of activation and entropy of activation were calculated and analyzed. Thermodynamic parameters for the adsorption of the inhibitor on the metal alloy surface were calculated and analyzed. The inhibitor acted as a mixed inhibitor. The mechanism of adsorption deduced from the variation of inhibition efficiency with temperature as well as kinetic and activation parameters suggests significant chemisorption of the inhibitor on the metal surface. The mechanism of inhibition can partly be attributed to the possible coordination of rutin to form stable aluminum–rutin complex. The maximum inhibition efficiency was found to be 95.1 and 94.45% by PDP and EIS studies, respectively, at 60 °C. Density functional theory calculations under the level B3LYP/6-311G(d) is utilized for the calculation of quantum chemical parameters.     

An analysis of the creep-environment interaction of Inconel alloy X-750 exposed at 1150°C

The effect of exposure of Inconel alloy X-750 to air at 1150°C on creep at 700°C and 400 MPa has been investigated. Contrary to the findings for exposure at 1050°C, exposure to air at 1150°C does not impair creep ductility. This is attributable to oxygen diffusion into the alloy at 1150°C being impeded. Evidence is given here to show that during exposure to air at 1150°C diffusion of chromium is fast enough to reach the surface and form a chromium oxide scale, which acts as a barrier to further oxygen diffusion.     

Magnetic properties and structure of cobalt-platinum thin films

The magnetic properties of RF sputtered Co-Pt alloy thin films were studied as a function of Pt content from 0 to 80 at%. At room temperature, ferromagnetic films were obtained in the range 0-32 and 40-80 at% Pt. For Pt contents between 32 and 40 at%, discontinuities in the magnetization, magnetostriction, and coercivity versus Pt content were observed; however no discontinuity was observed in the resistivity. The structure of films containing about 25 at% Pt is a mixture of hexagonal and face-centered cubic (FCC) phases. At this composition the magnetostriction is small, but coercivities are large-700 to 2000 Oe-and dependent upon film thickness. The coercivities of these films do not change with heat treatment up to temperatures of 600°C but decrease markedly at 700°C. The properties of equiatomic Co-Pt film s are similar to those of bulk alloys. In particular the large coercivity observed in films after heal treatment at 500° to 700°C is due to the formation of an ordered tetragonal phase within the face-centered cubic matrix. The structure of films of about 75 at% Pt is initially a disordered face-centered cubic phase and with heat treatment beginning at 500°C an ordered face-centered cubic phase forms. The coercivity of these films (∼200 Oe) does not change with annealing at 500°C. It decreases slightly upon further annealing at 600°C to 700°C. Electron microscope observations were used to correlate the magnetic properties with film structure.     

Preparation and corresponding structure of nickel foam

Abstract

A nickel foam with a three-dimensional reticulated structure has been prepared by an electrodeposition technique. The microcrystalline structure of the nickel layer was maintained following treatment in air at 600°C for 4 min. Sintering in a reductive decomposed NH₃ atmosphere for 40 min, at either 980 or 850°C, transformed the product into a compact nickel crystal with a flat surface and large crystal grains.     

Controllable synthesis of SnO2 photocatalyst with superior photocatalytic activity for the degradation of methylene blue dye solution

SnO₂ photocatalyst was successfully synthesised by novel chemical route in hydrothermal environment and annealed at two different temperatures viz 550 and 600 °C, respectively. The crystal structure, optical properties, surface and bulk morphology have been characterised using various tools like X-ray diffraction (XRD), UV visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). Cubic, spheres and porous like morphology of SnO₂ photocatalyst was successfully confirmed using SEM micrographs and TEM. In addition to this the photocatalytic activity was evaluated towards the degradation of methylene blue dye solution. SnO₂ photocatalyst annealed at 600 °C exhibits excellent photocatalytic efficiency which may be attributed to the unique morphology, high crystalline nature and charge separation. The photocatalyst efficiency was further tested towards the concentration of dye, catalyst dosage and pH of the dye. The involvement of ?OH in the photocatalytic reaction was evidenced using trapping experiment by employing different scavengers. The photocatalyst was moderately active, stable upto its fifth usage and stability of the photocatalyst before and after the photocatalytic reaction was also been studied using XRD and SEM.     

Development of high strength in Ni–42Cr–7·7Al (at.-%) alloy

Abstract

An investigation has been made of the aging of supersaturated nickel based solid solution in a Ni–42Cr–7·7 Al (at.-%) alloy. Solution treatment of the alloy in the range 1150–1300°Cfollowed by quenching and aging at ~550–750°C produces high values of hardness and strength, e.g. 835 HV on aging at 600°C. This hardening results from a discontinuous precipitation reaction producing a fine scale lamellar structure consisting of nickel based and chromium based solid solutions; interlamellar spacings of ~60 nm were obtained. The rate of precipitation is substantially greater than that in a binary Ni–42 at.-%Cr alloy.

MST/736     

Effects of solution heat treatment on grain growth and degree of sensitization of AISI 321 austenitic stainless steel

This work investigates the influence of solution temperature on grain growth and degree of sensitization of AISI 321 steel. Samples were solution treated at temperatures between 800 and 1,200°C for 80 min and sensitized at 600°C for 105 h. Optical microscopy and double loop electrochemical potentiodynamic reactivation (DLEPR) techniques were used to characterize and evaluate the degree of sensitization. The grain coarsening temperature (T_gc) found was 1,080°C, with occurrence of abnormal or discontinuous grain growth. Samples submitted to solution heat treatment below 1,080°C presented average grain diameter approximately equal to those presented by non-heat treated samples. The sensitization process at 600°C for 105 h became null when the samples were previously solution treated at 800 or 900°C, for 80 min. Sensitized and previously solution treated samples for temperatures greater than 1,075°C presented a decrease in sensitization intensity and an increase in transgranular precipitation.     

Fatigue life determination of plasma nitrided medical grade CoCrMo alloy

In this paper, the fatigue behaviour of plasma nitrided medical grade forged CoCrMo alloy was studied. Since metallic biomaterials are used for implant applications where high and/or cyclic stresses along with corrosive effects of human body are of concern, enhancing mechanical and surface properties of implant alloys is crucial. Plasma nitriding was implemented at three different temperatures as 600, 700 and 800 °C for time intervals of 1 and 4 h. S–N curves of untreated and nitrided specimens were obtained via axial tension compression fatigue tests. It was found that plasma nitriding treatment reduces the fatigue resistance of forged CoCrMo alloy by the ratios of 7–23% depending on the surface roughness, phase structure and hardness of the modified layer which are determined by the treatment parameters.     

Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2) alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C). The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.