锆合金电解渗氢工艺及组织演变研究

对新型Zr-Sn-Nb系SZA-4锆合金管材进行电解渗氢处理,研究了渗氢时间对SZA-4锆合金吸氢量和氢化物类型及分布的影响规律,以及均匀化退火对氢化物类型及分布的影响规律。结果表明,随着电解渗氢时间延长,SZA-4锆合金管材的吸氢量增加,吸氢量与渗氢时间之间符合抛物线关系。显微组织分析表明,锆合金电解渗氢后在样品表面形成一层氢化物层,而内部仍为锆合金基体。随着渗氢时间延长,该氢化物层的厚度增加。对氢化物层的相结构分析表明,渗氢时间较短时,氢化物层由δ-ZrH_1.66相组成;随着渗氢时间延长,氢化物层中的δ-ZrH_1.66相含量增加;渗氢24 h后,氢化物层由ε-ZrH_1.801相和δ-ZrH_1.66相组成。对渗氢试样400 ℃/6 h均匀化退火处理后,发现氢化物层厚度进一步增加,且在样品内部沿周向有条状氢化物析出。相结构分析显示,此时氢化物层中ε-ZrH_1.801相消失,原来的δ-ZrH_1.66氢化物转变为δ-ZrH_1.5氢化物。而经400 ℃/96 h均匀化退火处理后,氢化物层消失,细小条状氢化物均匀分布于试样中。     

第二相对Zr-Sn-Nb系锆合金吸氢性能的影响

对两种新型Zr-Sn-Nb系锆合金(SZA-4和SZA-6)管材在电解渗氢条件下的吸氢性能及机制进行了研究。结果表明,在供货状态下,SZA-4锆合金管材的吸氢倾向高于SZA-6锆合金管材,但经过完全再结晶退火处理后发现,SZA-4锆合金管材的吸氢倾向降低,而SZA-6锆合金管材的吸氢倾向增加,并且SZA-6锆合金管材的吸氢倾向反而高于SZA-4锆合金管材。与传统Zr-4合金管材相比,完全再结晶退火态的SZA-4和SZA-6锆合金管材在电解渗氢条件下的吸氢倾向均高于Zr-4合金管材。SZA-4和SZA-6锆合金管材吸氢倾向的变化与其内部析出的第二相有关。大量fcc结构的(Zr,Nb)2Fe第二相析出是导致完全再结晶退火态SZA-6锆合金吸氢倾向增加的主要原因。     

Zr1-xCoNbx (x = 0-0.2)合金吸放氢性能及抗歧化机制研究

采用真空电弧熔炼法制备了Zr_1-xCoNb_x (x = 0,0.05,0.1,0.15,0.2)合金,研究了Nb掺杂对合金晶体结构、吸放氢及抗歧化性能的影响。XRD结果表明：Zr_1-xCoNb_x (x = 0-0.2)合金主相为ZrCo相,含有少量ZrCo₂杂相;其氢化物为ZrCoH₃和ZrCo₂相。Nb掺杂极大地提高了合金吸氢动力学性能,ZrCo吸氢反应活化时间为7690 s,Zr_0.8CoNb_0.2缩短至380 s。ZrCo吸氢反应活化能为44.88 kJ mol^_-1 H₂,Zr_0.8CoNb_0.2降低至32.73 kJ mol^_-1 H₂,有利于吸氢反应动力学性能。DSC测量结果表明：ZrCo放氢温度为597.15 K,Zr_0.8CoNb_0.2降低至541.36 K,放氢温度降低,有利于抗歧化性能。ZrCo合金放氢反应活化能为100.55 kJ mol^_-1 H₂,Zr_0.8CoNb_0.2降低至84.58 kJ mol^_-1 H₂。合金歧化程度随着Nb掺杂量增加而降低,798 K保温10 h,ZrCo歧化83.68%,Zr_0.8CoNb_0.2仅歧化8.71%,Nb掺杂降低8f₂和8e位置氢原子数量,减小岐化反应驱动力。     

Pd71.5Cu12Si16.5金属玻璃的氢相关性能

钯基金属玻璃在氢相关工业中具有潜在的应用价值。在本工作中,我们通过电弧熔炼、铜辊甩带的方法制备了Pd_71.5Cu₁₂Si_16.5 金属玻璃的宽带样品。通过常规X射线衍射仪和短波长X射线应力分析仪的X射线衍射谱确定了样品的完全非晶态结构。在室温、100kPa压力条件下,对样品进行了多次的吸、放氢循环实验。经过10次以上的循环后,样品没有发生破坏,表现出良好的抗氢脆性能。通过气体直接渗透的方法进一步测试了Pd_71.5Cu₁₂Si_16.5 金属玻璃及其同成分晶态合金的氢渗透性能。在金属玻璃的过冷液相区温度范围内,其氢渗透率明显高于晶态相,这一结果由金属玻璃在该区间内的等温保持引入了更多的自由体积进行解释。     

Chou模型在La(Fe,Si)13基磁性材料中的研究应用

本文介绍了合金材料吸氢的基本原理及反应机理,主要利用稀土系储氢材料的吸氢模型方程研究了磁性制冷材料La(Fe,Si)₁₃基合金的吸氢特性。通过Chou模型建立了La_0.7Pr_0.3Fe_11.5Si_1.5和La_0.7Pr_0.3Fe_11.5Si_1.5C_0.2合金的吸氢反应分数与时间、温度的具体关系式,探究了两种合金材料的吸氢反应特性。根据模型方程,引入吸氢过程中的重要参数“特征反应时间”,得到在等温等压条件下的La_0.7Pr_0.3Fe_11.5Si_1.5和La_0.7Pr_0.3Fe_11.5Si_1.5C_0.2合金的吸氢反应分数随时间的变化曲线。由模型方程还得到这两种合金吸氢反应分数与温度的关系曲线,曲线表明两种合金均表现出温度越高,特征反应时间越小,合金的吸氢速率越快,与实验得到的结果一致。     

高铌钛铝合金高温固态置氢组织与高温变形行为

研究了高铌钛铝合金Ti-44Al-8Nb高温固态置氢处理组织演化规律,并考察了氢对高温变形行为的影响。研究结果表明,具有近片层组织结构的Ti-44Al-8Nb合金吸氢过程是吸热过程,合金的吸氢量随着置氢温度、置氢时间、氢流量的提高逐渐提高;在1200℃下进行固态置氢和等温热处理,置氢后的合金片层粗化,B2相含量较高;在T_α温度以上置氢后,氢降低界面能促使片层团界面光滑平整;氢对高铌钛铝合金的高温变形行为有明显的影响,在1200℃,应变速率为0.01s_-1下变形,添加0.043wt%H后,峰值应力降低40%。高温固态置氢能够有效改善高铌钛铝合金热加工性能。     

非化学计量La(NiMn)_(5.6)合金的储氢性能

借助X-ray及吸放氢性能测试装置研究了处理条件对非化学计量La(NiMn)5.6合金的结构、活化性能、吸氢容量和平台压力等性能的影响,测试了不同温度(298～333 K)下合金吸放氢性能的PCT曲线。结果表明,无论退火处理还是快速凝固,合金的点阵常数a缩短,c伸长,单胞体积增大。与常规熔铸相比,退火处理和快速凝固均提高了合金的活化性能,且都大大提高了合金的贮氢性能。都使平台压力降低,但快速凝固吸氢量有所降低;快速凝固+低温退火合金的吸氢量最大,在298 K、3.3 MPa下,PCT的最大吸氢原子比(H/M)为1.24。     

铒元素对锆基合金的非晶形成能力及力学性能的影响

以海绵锆为原料,采用水冷铜坩埚熔炼和铜模吸铸法制备了直径为3 mm、成分为(Zr_0.55Cu_0.3Al_0.1Ni_0.05)_100-xEr_x (x=0,0.5,1,2,3,4,5)的锆基块体合金,通过对比不同铒含量海绵锆基合金的组织结构与性能,研究了铒元素对其非晶形成能力、热稳定性和力学性能的影响。结果表明：以海绵锆为原料时,锆基合金的非晶形成能力和力学性能明显下降。x=0时,无法制备成锆基非晶合金;添加Er元素后,海绵锆基合金的非晶形成能力和力学性能显著提高,具有非晶态结构;x=2时,海绵锆基非晶合金的力学性能最优,抗压强度σ_bc为2142.5 MPa,室温下塑性应变ε_p为10.01%。与高纯锆制备的同直径(Zr_0.55Cu_0.3Al_0.1Ni_0.05)₉₈Er₂非晶合金相比,其抗压强度恢复97.63%,室温塑性恢复69.95%。添加铒元素有利于改善和提高海绵锆基合金的非晶形成能力和力学性能,为低成本制备锆基非晶合金提供一种新思路。     

Fe0.85Mn0.15Ti0.9M0.1（M=Zr,V,Ca）合金的贮氢性能

系统地研究了Ｆｅ０．８５Ｍｎ０．１５Ｔｉ０．９Ｍ０．１（Ｍ＝Ｚｒ,Ｖ,Ｃａ）合金的贮氢性能。研究结果表明：Ｆｅ０．８５Ｍｎ０．１５Ｔｉ０．９Ｚｒ０．１合金在室温下经几分钟的孕育期就可吸氢,但合金在氢化过程中形成了氢含量很高的α相,导致合金的贮氢量降低,同时还使ｐ－ｃ－Ｔ曲线的平台特性变差;Ｆｅ０．８５Ｍｎ０１５Ｔｉ０．９Ｖ０．１合金的活化性能进上步得到改善,在室温下几乎不需要孕育期就可以吸氢,但同     

微量镍元素添加对Zr-4合金微观结构、耐腐蚀性能及吸氢行为的影响

将微量镍元素合金化添加到Zr-4合金中，制备了合金板材试样。利用板材试样研究了微量镍元素的添加对Zr-4合金微观结构、耐腐蚀及吸氢性能的影响。结果表明，将镍元素含量由海绵锆原料中的0.001%（质量分数）以下添加至0.005%，可大幅提升其400 ℃蒸汽下耐腐蚀性能，同时对吸氢性能没有明显影响。微量镍元素的添加，不仅使Zr(Fe, Ni)₂结构的第二相粒子明显增加，同时还促进了硅在第二相粒子周围的偏聚，这可以阻止或延缓细小第二相粒子被氧化的进程。进一步采用相同合金成分制备的锆管（Φ63.5 mm×10.92 mm），也呈现出了优异的耐疖状腐蚀和耐均匀腐蚀性能。     

Kinetics of Hydrogen Absorption in Ti-V-Cr Burn-Resistant Alloy

研究Ti40合金在550～700°C温度区间的吸氢动力学,初始氢压为15.88～45.88kPa。研究表明,Ti40合金初始吸氢温度为515°C,吸氢时达到平衡所需的时间随着温度和初始氢压的增加而缩短,而吸氢速率和平衡氢压随着温度和初始氢压的增加而增加。在低温时,吸氢过程包括3个阶段:Ⅰ孕育期,Ⅱ第1吸氢阶段和Ⅲ第2吸氢阶段。在相同温度下,不同阶段的速率常数遵循以下关系:kⅡ>kⅠ>kⅢ。在相同阶段,速率常数随温度的升高而增大。吸氢过程中第1和第2吸氢阶段的激活能分别为73.3和29.6kJ/mol。第2吸氢阶段的速率控制步骤为氢在β-Ti中的扩散。     

Hydrogen absorption and desorption in Ti−Al alloys

Binary Ti_1−xAl_x and ternary Ti_0.75−xAl_0.25M_x (M=V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Pd, Hf, Ta and W; x=0.15 and 0.25) alloys reacted slowly with 5.0 MPa H₂ at room temperature for different periods. The hydrogen absorption capacity, the 50% hydrogen desorption temperature (T _d) and the structures of their hydride were investigated. Amorphous and fcc type hydrides formed by hydrogenation of the binary Ti−Al alloys. As the Al concentration increased in the Ti−Al alloys, the hydrogen absorption capacity decreased, while the hydrogen desorption temperature decreased at once and then increased again. Amorphous, fcc, bcc and C14 Laves type hydrides formed by hydrogenation of the ternary Ti₃Al− based alloys. The hydrogen absorption capacity was reduced despite whatever elements were substituted for Ti in Ti₃Al. Ni, Co, Mn and Nb have the ability to reduceT _d of Ti_0.75−xAl_0.25M_x. This article based on a presentation made in the symposium “The 2nd KIM-JIM Joint Symposium: Hydrogen Absorbing Materials”, held at Hanyang University, Seoul, Korea, October 27–28, 2000 under the auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

Corrosion and hydrogen absorption of commercially pure zirconium in acid fluoride solutions

The corrosion and hydrogen absorption of commercially pure zirconium have been investigated in acidulated phosphate fluoride (APF) solutions. Upon immersion in 2.0% APF solution of pH 5.0 at 25 °C, a granular corrosion product (Na₃ZrF₇) deposits over the entire side surface of the specimen, thereby inhibiting further corrosion. In 0.2% APF solution, marked corrosion is observed from the early stage of immersion; no deposition of the corrosion product is observed by scanning electron microscopy. A substantial amount of hydrogen absorption is confirmed in both APF solutions by hydrogen thermal desorption analysis. The amount of absorbed hydrogen of the specimen immersed in the 2.0% APF solution is smaller than that in the 0.2% APF solution in the early stage of immersion. The hydrogen absorption behavior is not always consistent with the corrosion behavior. Hydrogen thermal desorption occurs in the temperature range of 300–700 °C for the specimen without the corrosion product. Under the same immersion conditions, the amount of absorbed hydrogen in commercially pure zirconium is smaller than that in commercially pure titanium as reported previously. The present results suggest that commercially pure zirconium, compared with commercially pure titanium, is highly resistant to hydrogen absorption, although corrosion occurs in fluoride solutions.     

Hydrogen storage performances of as-milled REMg11Ni (RE=Y,Sm) alloys catalyzed by MoS2

To compare the hydrogen storage performances of as-milled REMg₁₁Ni-5MoS₂ (mass fraction) (RE=Y, Sm) alloys, which were catalyzed by MoS₂, the corresponding alloys were prepared. The hydrogen storage performaces of these alloys were measured by various methods, such as XRD, TEM, automatic Sievert apparatus, TG and DSC. The results reveal that both of the as-milled alloys exhibit a nanocrystalline and amorphous structure. The RE=Y alloy shows a larger hydrogen absorption capacity, faster hydriding rate, lower initial hydrogen desorption temperature, superior hydrogen desorption property, and lower hydrogen desorption activation energy, which is thought to be the reason of its better hydrogen storage kinetics, as compared with RE=Sm alloy.     

Enhancement of Ti-Cr-V BCC alloys on the dehydrogenation kinetics of Li-Mg-N-H hydrogen storage materials

The hydrogen storage properties of a Li-Mg-N-H material doped by a 4 mol.% Ti₃Cr₃V₄ body centre cubic (BCC) alloy hydride and prepared with a ball-milling method were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Sievert’s technology test. The results show that the Ti₃Cr₃V₄ BCC alloy hydride/Li-Mg-N-H composite has good reversible hydrogen storage properties. The dehydrogenation kinetics of the Li-Mg-N-H system can be greatly improved by doping the Ti₃Cr₃V₄ BCC alloy hydride. The composite desorbed 4.1 wt.% hydrogen in the first 60 min at 473 K under 0.1 MPa pressure, but when without the BCC alloy addition, only 3.0 wt.% hydrogen was desorbed under the same dehydrogenation condition. It can be deduced that the Ti₃Cr₃V₄ BCC alloy uniformly distributed in the Li-Mg-N-H substrate could decrease the activating energy of hydrogen molecules to H atoms and increase H diffusion paths in the composite, enhancing the dehydrogenation kinetics of the Li-Mg-N-H system.     

Evolution of dielectric properties in BaZrxTi1−xO3 ceramics: Effect of polar nano-regions

BaZr_xTi_1?xO₃ (x = 0.2, 0.25, 0.3) ceramics were prepared by a citrate method. The ferroelectric phase transition behavior and bias electric-field-induced dielectric nonlinearity of the ceramics were investigated. With increasing zirconium content, the phase transition behavior of the ceramics changed from a diffusion phase transition to relaxor-like behavior. Applying bias electric field in diverse manners led to differing effects on the dielectric nonlinearity, depending on the zirconium content of the ceramics. These dielectric phenomena were related to the polarization response of polar nano-regions (PNRs) embedded in the ceramics, which are macroscopically in the paraelectric state at room temperature. The characteristic parameters of PNRs were determined by fitting the dielectric constants under bias electric field to a multipolarization mechanism model. It was found that the size of PNRs was decreased with increasing zirconium content. The evolution of the phase transition behavior and dielectric nonlinearity with zirconium content was interpreted in relation to the size change of PNRs.     

ABSORPTION KINETICS OF HYDROGEN SULPHIDE USING ISOTHERMAL AND ISOVOLUMETRIC METHOD

ＡＢＳＯＲＰＴＩＯＮＫＩＮＥＴＩＣＳＯＦＨＹＤＲＯＧＥＮＳＵＬＰＨＩＤＥＵＳＩＮＧＩＳＯＴＨＥＲＭＡＬＡＮＤＩＳＯＶＯＬＵＭＥＴＲＩＣＭＥＴＨＯＤＨａｉＭｉｎｇｔａｎ；ＬｉｕＣｈａｎｇｑｉｎｇ；ＺｈａｎｇＰｉｎｇｍｉｎ；ＣｈｅｎＱｉｙｕａｎ（Ｄｅｐａ...     

Ti-10Mo双相合金的吸氢性能

研究了低温(90℃以下)和高温(400—500℃)吸氢循环两种活化方法对Ti—1OMo双相合金吸氢动力学特性及吸氢后抗粉碎能力的影响．发现高温活化样品的抗破裂能力优于低温活化样品，但低温活化样品的吸氢动力学性能明显优于高温活化样品，这一现象可用样品具有不同的吸氢受控机制和相变过程来解释．     

Improved hydrogenation properties of Mg-x(Ti0.9 Zr0.2 Mn1.5 Cr0.3) composites

Mg-x(Ti_0.9 Zr_0.2 Mn_1.5 Cr_0.3)(x=20%, 30%, 40%) (mass fraction) composite powders were prepared by reactive ball milling with hydrogen and their hydrogen storage properties and microstructure were investigated by XRD, SEM and pressure-composition-temperature measurement. The results show that the composites have 3.83%-5.07% hydrogen capacity at 553 K and good hydrogenation kinetics, even at room temperature. Among them, the milled Mg-30%(Ti_0.9Zr_0.2Mn_1.5Cr_0.3) composite has the highest hydrogenation kinetics as it can quickly absorb 2.1% hydrogen at 373 K, 3.5% in 2 000 s at 473 K, even 3.26% in 60 s at 553 K under 3 MPa hydrogen pressure. The improved hydrogenation properties come from the catalytic effect of Ti_0.9 Zr_0.2 Mn_1.5 Cr_0.3 particles dispersed uniformly on the surface of Mg particles.     

Hydrogen uptake in 316L stainless steel: Consequences on the tensile properties

Different charging conditions aimed at introducing significant hydrogen concentrations without microstructural damages in a 316L austenitic stainless steel were investigated. The equivalent hydrogen pressure developed at the surface of the samples during cathodic charging was estimated from hydrogen concentration measurements. A clear hydrogen absorption, controlled by diffusion, was evidenced during the immersion of 316L steel samples in 30% MgCl₂ at the open circuit potential at 117 °C. Deuterium profiling by SIMS was performed to check the validity of the few literature data on hydrogen diffusivity in the near room temperature range in this material. On the other hand, the macroscopic effects of hydrogen on the tensile characteristics of the steel were investigated and compared at 20 °C and at −196 °C with samples cathodically pre-charged, charged during tensile straining or pre-charged at high temperature-high pressure in gas phase. Hydrogen is shown to affect both the short range and the long range forces exerted on the strain-induced mobile dislocations. The hydrogen-induced softening effect observed at 20 °C and the systematic decrease of the ductility support a mechanism involving the enhanced transport of hydrogen atoms by mobile dislocations. This mechanism is confirmed by the absence of softening and of ductility loss at −196 °C and by the strain-enhanced tritium desorption from samples cathodically pre-charged with tritium, measured by β counting during tensile deformation.