Healing of hydrogen-attacked cracks in split specimens with recovering heat treatment in vacuum

The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.

Effect of Heat-Treatment Process on Properties of Rare Earth Mg-Based System Hydrogen Storage Alloys with AB_3-Type

The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.

Influences of heat treatment on electrochemical characteristics of La_(0.75)Mg_(0.25)Ni_(2.8)Co_(0.5) hydrogen storage electrode alloy

The influences of annealing treatment on the electrochemical and structural properties of La 0.75Mg 0.25- Ni 2.8Co 0.5 hydrogen storage alloy were investigated by means of electrochemical studies and X-ray diffraction(XRD) analyses. The XRD results reveal that the peak width gets narrower with increasing annealing temperature, which can be ascribed to the structural change and more homogeneous composition after being annealed. Electrochemical studies show that the discharge capacity and the cycle stability of the alloy electrodes increase after being annealed. The maximum discharge capacity, exchange current density J 0 and limiting current density J L of the as-cast alloy are 388 mA·h/g, 340.5 mA/g and 3 068 mA/g, respectively, and they are increased to 400 mA·h/g, 372.1 mA/g and 3 399 mA/g for the alloy annealed at 1 123 K for 8 h, respectively. Meanwhile, as the discharge current density is 1 250 mA/g, the high rate dischargeability(HRD) increases from 77.4% for the as-cast alloy to 83.3% for the alloy annealed at 1 123 K.

CO_2 selective hydrogenation to synthetic natural gas(SNG) over four nano-sized Ni/ZrO_2 samples:ZrO_2 crystalline phase & treatment impact

Two type zirconia (monoclinic and tetragonal phase ZrO2) carriers were synthesized via hydrothermal route, and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300 °C to 500 °C, for the CO2selective hydrogenation to synthetic natural gas (SNG). The catalysts were characterized by XRD, CO2-TPD-MS, XPS, TPSR (CH4, CO2) techniques. For comparison, the catalyst NZ-W-400 (monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400 (tetragonal) prepared in methanol solvent. The catalyst NZ-W-400 displayed more H2absorbed sites, more basic sites and a lower temperature of initial CO2activation. Then, the thermal treatment of monoclinic ZrO2supported nickel precursor was manufactured at three temperature of 350, 400, 500 °C. The TPSR experiments displayed that there were the lower temperature for CO2activation and initial conversion (185 °C) as well as the lower peak temperature of CH4generation (318 °C), for the catalyst calcined at 500 °C. This sample contained the more basic sites and the higher catalytic activity, evidenced byCO2-TPD-MS and performance measurement. As for the NZ-W-350 sample, which exhibited the less basic sites and the lower catalytic activity, its initial temperature for CO2activation and conversion was higher (214 °C) as well as the higher peak temperature of CH4formation (382 °C). © 2016 Science Press

V-Ti-Fe三元合金显微组织、氢传输行为及耐蚀性能研究

Nb-Ti-Fe双相合金已被证实具有优异的渗氢性能,有望成为替代传统Pd膜的渗氢材料。V和Nb同属于5B族,具有类似的物理化学性质,但是,V-Ti-Fe双相合金组织转变规律和渗氢性能至今无人研究。基于此,本工作对V-Ti-Fe三元合金的显微组织和渗氢行为开展了详细研究,并探索了热处理和电化学腐蚀对改善渗氢性能的可能性。研究结果表明:V-Ti-Fe三元合金体系中存在一个包共晶凝固反应,即L+TiFe_(2)→Bcc-(V,Ti)+TiFe(1626 K)。液相面投影图中存在三个相区,分别为TiFe相区、TiFe_(2)相区和Bcc-(V,Ti)相区。其中,TiFe相区合金室温组织由初生TiFe相和{Bcc-(V,Ti)+TiFe}共晶结构组成,TiFe_(2)相区合金室温组织由初生TiFe相、TiFe_(2)相和Bcc-(V,Ti)相构成,Bcc-(V,Ti)相区合金室温组织由初生Bcc-(V,Ti)相和TiFe相组成,渗氢性能测试证实了该系合金抗氢脆性能较弱。具体来说,上述三区域内部铸态合金在渗氢实验前均发生了不同程度的破碎,仅V_(2.5)Ti_(62.5)Fe_(35)合金能够渗氢,不过,该合金在渗氢后期发生断裂。最后,本工作采用电化学腐蚀和真空热处理两种方法改善该合金体系的渗氢性能,其中,V_(2.5)Ti_(62.5)Fe_(35)合金具有较高的耐腐蚀性能,经热处理后该合金的渗氢性能明显提升,其在623 K下的氢渗透性能为1.03×10^(-9)mol H_(2)m^(-1)·s^(-1)·Pa^(-0.5)。

热成型钢氢脆行为研究进展

提高汽车用钢的强度是实现汽车轻量化设计的有效途径。然而,随着热成型钢强度不断提高,其氢脆敏感性也相应增大,氢致开裂已成为阻碍超高强度热成型钢发展与应用的重要问题。对热成型钢氢脆的影响因素、研究方法、机理和防护方法这4个方面的最新研究进展进行了综述,为相关领域的研究人员提供参考。

掺氢天然气管道氢脆防护研究进展

结合目前掺氢天然气研究现状,从管线钢氢脆的角度,根据管线服役环境提出几种氢脆防止措施:可以单独或者协同竞争吸附来抑制氢脆的CO、CH 4、O 2等抑制性气体;常见的合金涂层以及具有高阻氢性能的二维新型材料(石墨烯、BN、MXene和TMDs);通过热处理和添加合金元素对管线钢改性,包括热处理调整组织与晶界、添加合金元素增加阻氢析出物等。

空气气氛热处理对Pd膜氢渗透性能的影响

为了研究空气气氛热处理对Pd膜氢渗透性能的影响,采用化学镀沉积Pd膜,并对在573 K空气气氛热处理前后的Pd膜氢渗透性能进行分析评价。用X射线衍射(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)和氢渗透方法对Pd膜进行了表征,结果表明:沉积态Pd膜结构致密无缺陷,厚度为5μm左右,Pd膜在673、723、773 K的氢渗透率分别为3.62×10^(-9)、5.12×10^(-9)、6.80×10^(-9)mol/(m·s·Pa^(0.5))。573 K空气气氛热处理会导致Pd膜表面粗糙度增加,表面积增大,氢在膜表面的解离吸附位点增加,进而提升膜的氢渗透性能。热处理后,Pd膜在673、723、773 K的氢渗透率分别为5.32×10^(-9)、6.44×10^(-9)、7.31×10^(-9)mol/(m·s·Pa^(0.5)),较热处理前提高了1.1~1.5倍。

钒基储氢合金的特点和应用前景

钒基储氢合金具有储氢密度高、储放氢反应条件温和、储氢动力学性能优越、抗粉化性能好等优点,是一种优良的储氢材料。但是钒基储氢合金存在放氢平台压低、可逆储氢量低、储放氢滞后现象明显、循环稳定性差、原料价格高、金属成本高等缺点,制约着钒基储氢合金进一步推广应用。迄今为止,研究者们从元素组成和晶相结构等多种途径对其进行改性,以优化钒基储氢材料性能。基于此,以降低氢化物的放氢平台压和提高材料可逆储氢量为出发点,简述了掺杂Ti,Cr,Mn,Zr等化学元素和对于储氢合金进行特定条件优化改善的研究进展,着重阐述了元素置换、材料热处理和合金活化预处理对钒基储氢合金储氢性能的影响,展望了钒基储氢合金未来发展前景。

油气输送用管线钢组织及性能研究进展

管线钢是石油、天然气输送中用到的一种特殊钢材,其组织和性能是研究者关注的重点。本文综述了油气输送用管线钢组织及性能的最新研究成果,从添加合金元素和稀土、热处理两个维度总结了其对组织和性能的影响。研究发现,添加稀土和合金元素会对管线钢的性能造成不同程度的影响,不同钢级的管线钢的不同热处理工艺对性能的影响也不尽相同,最后展望了管线钢未来发展的方向。

Phase transformation behavior of a TiNiCu shape memory alloy electro-lytically charged with hydrogen

The transformation behavior of a TiNiCu shape memory alloy electrolyticallycharged with hydrogen was investigated by means of different scanning calorimetry (DSC), opticalmicroscope and X-ray diffraction (XRD). The results showed that inter- and inner-granular hydridesformed after charging with hydrogen, and the hydrides suppressed martensitic transformation. Theelectrolytically charged hydrogen can be easily released by heat treatment and the transformationoccurred again, which was verified by the DSC and XRD experiments.

AB_5-type Hydrogen Storage Alloy Modified with Ti/Zr Used as Anodic Materials in Borohydride Fuel Cell

Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hydrogen and enhance the utilization of borohydride, Ti/Zr metal powders has been added into the parent LmNi4.78Mn0.22 （where Lm is La-richened mischmetal） alloy （LNM） by ball milling and heat treatment methods. It is found that the addition of Ti/Zr metal powders lowers the electrochemical catalytic activity of the electrodes, at the same time, restrains the generation of hydrogen and enhances the utilization of the fuel. All the results show that the hydrogen generation rate or the utilization of the fuel is directly relative to the electrochemical catalytic activity or the discharge capability of the electrodes. The utilization of the fuel increases with discharge current density. It is very important to find a balance between the discharge capability and the utilization of the fuel.

导电炭黑和热处理对Al-Bi复合材料产氢性能的影响

采用机械球磨法制备Al-Bi-CB复合材料,研究了导电炭黑和热处理对Al-Bi复合材料产氢性能的影响,用扫描电子显微镜和X射线衍射仪分析了复合材料的组织形貌和物相结构。实验结果表明,当导电炭黑含量为5%时,复合材料的产氢性能最佳。在30℃时,1 g Al-3%Bi-5%CB复合材料5 min产生865 mL氢气,最大产氢速率达到107.15 mL·s^(-1)。导电炭黑细化铝粉体颗粒、提高Al-Bi复合材料的导电性以及与水接触时导电炭黑能迅速从复合材料表面剥落是其提高Al-Bi复合材料产氢量和产氢速率的主要原因。球磨Al-Bi-CB粉体材料经热处理后,在30 min内,1 g Al-3%Bi-1%CB材料的最大产氢量从220 mL增至840 mL,热处理后嵌入Al中的Bi重新熔化与再结晶而覆盖在Al表面形成活性位点是提高复合材料产氢性能的主要原因。

快速热解铂前体合成高分散的Pt/HY催化剂及其萘深度加氢性能

十氢萘不仅可以作为高档溶剂,也是航空煤油的重要添加剂,通过焦化萘深度加氢合成十氢萘具有重要的工业价值。本文以乙酰丙酮铂作为前体物理气相沉积到HY沸石孔道中,通过高温快速热解有机配体获得了高分散的负载型Pt基催化剂。通过XRD、N_(2)吸附、CO-DRIFT、HRTEM、H_(2)-TPR和XPS等对催化剂的结构和性质进行了系统表征。与传统的高温煅烧不同,经快速热处理制备的Pt/HY催化剂中Pt粒径较小且分布均匀,在温和的反应条件(H_(2)3MPa、100℃、1h)下对萘具有优异的深度加氢性能,萘的转化率及十氢萘的产率均达到99.9%,且TOF值高达2171h^(-1)。实验结果表明,铂在催化剂上的高分散以及部分正价态铂物种的存在有助于萘深度加氢合成十氢萘。研究结果对于制备用于萘深度加氢的高效Pt基催化剂具有一定指导意义。

热处理对特种设备用高强钢激光–电弧复合焊接头氢脆断裂行为的影响研究

目的提高800 MPa级特种设备用低碳贝氏体高强钢激光–电弧复合焊接头的抗氢脆性能。方法采用预充氢后慢应变速率拉伸试样的方法,定量评估焊态、焊后直接高温回火和焊后调质3种状态下800 MPa级低碳贝氏体高强钢激光–电弧复合焊接头的氢脆敏感性,结合扫描电镜下的初始微观组织和断裂特征,讨论抗氢脆性能的改善机理。结果焊后调质处理有效消除了焊接热循环形成的马氏体组织,使接头各区域的微观组织趋于一致,接头的抗氢脆性能较焊态和直接焊后高温回火态的显著提高,断裂特征也从沿晶和穿晶的混合断裂转变为穿晶解理断裂。结论焊后调质处理可以有效提高800 MPa级低碳贝氏体高强钢激光–电弧复合焊接头的抗氢脆性能。

Hydrogen Absorption and Desorption during Heat Treatment of AISI 4140 Steel

Hydrogen plays an important role in the formation of quench cracks of structural steels. To clarify hydrogen ab- sorption and desorption during heat treatment of AISI 4140 steel, thermal desorption spectrometry （TDS） analysis was carried out for the specimens in the as-rolled, as quenched, and quenched and tempered conditions. Results show that hydrogen content increased from 0. 127 ×10 6 in the as-rolled specimen to 0. 316 × 10-6 in the as-oil-quenched specimen. After tempering at 200 ℃, the hydrogen content in the oil-quenched specimen decreased to 0. 155 × 10-6 , and the peak temperature of hydrogen desorption increased from 200 to 360 ℃. From the dependence of hydrogen content in the as-quenched specimens on austenitizing time, it can be deduced that hydrogen absorption occurs during austenitizing. The simulation of hydrogen absorption contributes to a better understanding on the distribution of hy- drogen during the heat treatment in structural steels.

汽车发动机前制动软管螺栓断裂原因

某汽车发动机前制动软管螺栓发生断裂现象,采用宏观观察、化学成分分析、扫描电镜分析、金相检验、硬度测试等方法分析了螺栓断裂的原因。结果表明:未对螺栓进行热处理,导致冷作硬化没有消除;在酸洗电镀工序中,氢离子浸入螺栓的根部,使螺栓根部发生氢致延迟断裂。

合金结构钢在RX气为保护气氛中加热的吸氢研究

利用HTDS-002型试验机,分别对典型合金结构钢试棒在RX气为保护气氛下进行淬火和无保护气氛下回火后的氢含量进行检测,获得了合金结构钢热处理过程的吸氢规律,基于检测结果,得出了合金结构钢在RX气为保护气氛下热处理的氢脆影响结论。最后,经过与无保护气氛加热试棒的力学性能进行比对,验证了合金结构钢在RX气为保护气氛下淬火+回火后不会产生氢脆的结论。另外,对常用合金结构钢的渗碳淬火工艺的每个工序进行吸氢检测,得到了合金结构钢渗碳淬火工艺过程的吸氢规律。

含铜铸钢件塑性不合原因分析及改进措施

对含铜铸钢件力学性能检测试样断口宏观形貌、微观形貌、金相组织、化学成分等进行分析,确定该含铜铸钢件塑性不合的原因,提出改进措施。经扩氢理论计算和生产实践验证,采用对应措施后,该含铜铸钢件的塑性得到改善提升。

TP321高压加氢管道再热裂纹影响因素与对策

为改善高压加氢管道焊接质量,减少焊后再热裂纹产生的概率,通过分析再热裂纹实际案例,找出了TP321不锈钢再热裂纹产生原因,重新进行了管道焊接工艺评定,制定了满足要求的焊接质量控制方法和焊后热处理措施。对焊接试件分别进行了力学性能测试、残余应力检测、晶间腐蚀试验、金相检验、高温缓慢拉伸试验,总结出再热裂纹影响因素,并提出了应对策略。在渣油加氢管道的应用结果表明:壁厚小于40 mm采取稳定化热处理的管道未出现再热裂纹;壁厚大于40 mm未采取热处理的管道,使用和停车期间未出现应力腐蚀现象,均保证了渣油加氢管道的焊接质量。