核废料玻璃固化国际研究进展

玻璃体对不同元素有着广泛的包容性,且具有良好的耐久性,除此之外,玻璃生产工艺简单,易于遥控操作,因而,玻璃固化技术是目前国际上唯一工业应用且发展最成熟的高放废液处理技术。从材料学的角度,介绍了玻璃固化核废料的机理及设计核废料玻璃固化体的基本原则,综述了玻璃固化体近年来的国际研究进展。重点研究方向包括:1以提高核废料负载量为目标,研究玻璃体对核废料的承载能力;2最大化核废料玻璃产率,研究玻璃炉料熔融物理化学反应;3确保核废料玻璃长期贮存的安全,研究玻璃腐蚀机理,建立长期腐蚀行为模型,提供玻璃固化体安全评价方法。最后,对核废料玻璃固化体今后的研究发展方向做了展望。     

高温时效后的310不锈钢高温硫腐蚀研究

研究了310不锈钢在气氛总压为10^-5Pa,于2.3％SO2－S2－8.8％N2气氛中600℃下的高温硫腐蚀行为。利用金相、能谱及X射线衍射等分析手段对其腐蚀形貌、成分及结构进行了分析。结果表明：310不锈钢于700℃,10000h时效在其晶界大量析出σ相,造成晶界附近贫Cr,从而降低了晶界抗硫腐蚀性能,使高温时效处理后的310不锈钢6抗硫腐蚀能力明显降低,未时效处理的310不锈钢以均匀腐蚀为主,时效处理后的则以晶界腐蚀为主,并伴随有均匀腐蚀。     

铝锌合金在镁合金AZ91D中的扩渗机理及腐蚀性能研究

采用包埋铝和锌的方法在镁合金AZ91D表面制备了铝-锌合金化涂层,并且利用x射线衍射、能谱分析研究了该涂层的组织和耐腐蚀性能。该涂层外层为AlMg2Zn, Mg7Zn3 和Mg17Al12 金属间化合物层;内层为Mg17Al12金属间化合物分布于α-Mg晶界。研究表明,与镁合金基体相比较在质量分数为3.5wt.% NaCl扩渗层显示出较好的耐腐蚀性能。盐雾腐蚀说明,Al-Mg-Zn合金化扩渗层对于降低腐蚀速率起到有效作用。此外,合金化扩渗层与基体的结合是冶金结合,且涂层的显微硬度显著提高。     

熔融锌液腐蚀的研究现状

对热镀锌连续生产中受熔融金属腐蚀部件的防护现状进行了分析,目前的研究工作可分为两大类:选择整体材料和表面处理.由于采用整体材料生产成本太高,且其耐熔融锌液腐蚀性能提高有限,采用表面处理提高抗锌液腐蚀成为目前研究的重点.表面处理有扩散渗硼、热喷涂层以及表面涂覆、隔离等方法,这些方法各有其特点.最后,对材料在熔融金属的现有腐蚀机理进行了总结,并指出了今后的发展方向.     

不锈钢在熔融NaCl中的电化学-化学-稀释模型

为分析不锈钢在熔融NaCl中的腐蚀机制,通过850℃熔融NaCl完全浸没实验,测量了168 h内3种不锈钢的腐蚀动力学曲线,借助SEM、EPMA、EDS等设备表征了试样横截面形貌、元素分布等特征,研究了Ti元素对合金耐蚀性影响机制,采用X射线衍射仪检测了腐蚀24h后熔融盐成分和168 h后试样表面成分,建立了电化学-化学-稀释联合作用腐蚀模型.结果表明:在熔融NaCl腐蚀介质中,金属材料作为阳极被溶解,吸附氧得到电子变成O2-作为阴极;金属阳离子与O2-在熔融NaCl中发生化学反应,生成易挥发性氯化物逃逸系统;熔融盐作为传质媒介,稀释腐蚀层区域的腐蚀产物浓度,提高腐蚀速度.合金中电极电位最负的微量组元优先溶解后形成微小孔隙,增大了微阳极表面积,加速腐蚀反应过程.     

熔盐堆用镍基合金在熔融氟盐中的腐蚀研究进展

熔盐堆(Molten salt reactor,MSR)是第四代先进核反应堆中唯一的液态燃料反应堆,因在热转化效率、中子经济性、固有安全性、在线燃料循环、核废料处理等方面具有无可比拟的优势而备受国内外研究者的关注。熔盐的选择对MSR的运行安全及效率至关重要。熔融氟化盐如LiF-BeF2(FLiBe)、LiF-NaF-KF(FLiNaK)等具有较小的热中子吸收截面、高热导率、高比热容、良好的流动性、低的蒸气压(高温时)、良好的高温稳定性等一系列优异的热物化性能,被公认为MSR最理想的冷却剂和核燃料载体。目前,国内外均选用镍基合金作为MSR的主要结构材料。然而,超强高温腐蚀性熔融氟盐的存在对镍基合金提出了苛刻的要求。目前,国内外学者们对熔盐堆用镍基合金在熔融氟盐中腐蚀行为的研究主要集中在两个方面:一是镍基合金在熔融氟盐中热腐蚀行为的影响因素及微观机制,二是提高镍基合金的耐高温熔盐腐蚀性能。一般认为,镍基合金在熔融氟盐中的腐蚀机制主要包括以下四种:本质腐蚀、氧化性杂质引起的腐蚀、温差驱动的腐蚀和异种材料引起的腐蚀。因此,合金自身和熔盐腐蚀环境是影响镍基合金在氟盐中热腐蚀行为的两大主要因素。在合金自身方面,主要为合金元素(Ni、Cr、Mo、Fe、Si等)及含量、合金显微组织(晶界特征、组织缺陷等)的影响;在熔盐腐蚀环境方面,主要为熔盐组分、熔盐中的杂质及腐蚀产物、熔盐温度、坩埚材质、核裂变产物等的影响。目前,提高镍基合金耐熔盐腐蚀性能的主要途径有:在镍基合金方面,包括有微合金化(添加Ti、RE等)、晶界工程处理、陶瓷相增强复合材料技术;在熔盐方面,包括熔盐纯化、添加单质金属(如Zr、Be、Li等)降低熔盐的氧化还原势等。此外,采用电镀法、激光熔覆法、化学气相沉积法、等离子喷涂法等表面改性技术在镍基合金上制备金属涂层(Ni、Co、Mo、NiCoCrAlY等)和陶瓷涂层(氮化物如AlN、碳化物如SiC)。本文重点综述了镍基合金在熔融氟盐中热腐蚀行为的主要影响因素及微观机制,以及国内外研究者在提高镍基合金耐高温熔盐腐蚀性能方面的研究进展。针对当前已开发的镍基合金与强腐蚀性的熔融氟盐相容性亟待解决的一些关键基础问题,提出了未来镍基合金在熔融氟盐工程应用中的主要技术方向和发展趋势,为耐高温氟盐腐蚀材料的研究和开发提供重要思路。     

纯镁材表面Zn，Al混合粉合金扩渗层形成的机制

根据纯镁材在扩渗温度不变的条件下,扩渗合金层形成特征随着扩渗时间的变化.研究了纯镁表面扩渗(Zn,Al)合金层的形成机制.结果表明:扩渗温度在390℃时,表面合金化过程中反应扩渗机理是镁表面合金化过程的关键阶段;扩渗时间由4 h延长至8 h,开始形成Al6Mg10Zn金属间化合物反应层,随后进一步发展为更加稳定的Al5Mg11Zn4金属间化合物.Zn元素的扩渗量对Al6Mg10Zn和Al5Mg11Zn4的转换起主控作用,并建立了相应的扩渗合金化模型.     

金属Tb晶界扩散对烧结钕铁硼磁性和耐温性的影响

本文采用了真空多弧离子镀的方法在烧结钕铁硼磁体表面沉积Tb金属薄膜,并对镀膜磁体进行真空热处理,使表面的Tb金属向磁体内部晶界扩散,研究经过金属Tb晶界扩散处理的磁体的磁性和耐温性。结果表明,经过晶界扩散处理,金属Tb进入了距离钕铁硼磁体表层一定深度范围内的晶界中,磁体的内禀矫顽力Hcj提高了9000～10000Oe,磁体的高温不可逆磁损失大幅降低,磁体的内禀矫顽力和耐温性能显著提高。     

Ni2＋掺杂聚苯胺膜的制备及其抗腐蚀性能

聚苯胺是最常用的一种导电聚合物,它作为腐蚀抑制剂覆盖在金属表面并形成一层很薄的保护膜,可以降低金属的腐蚀速度。采用循环伏安法在不锈钢表面电化学合成掺杂态（NiH）聚苯胺膜。利用极化曲线法和交流阻抗法研究了掺杂态聚苯胺膜的耐腐蚀性能及其影响因素。结果表明：在3．5％NaCl溶液中,不锈钢表面覆盖掺杂态聚苯胺膜的腐蚀电位比...     

国内外玻璃行业用高温耐蚀材料的研究进展

叙述了国内外玻璃工业常用高温耐蚀材料的应用现状，并就其中的金属及合金材料在熔融玻璃中的腐蚀机理作了介绍。另外，还对未来玻璃工业用高温耐蚀材料的发展趋势作出了展望。     

316L和Hastelloy C合金在不同温度循环废酸中的耐蚀性能

为了解316L和HastelloyC合金在不同温度的循环废酸中的耐蚀性能,利用静态挂片试验、电化学试验和扫描电镜研究了2种合金在不同温度循环废酸中的腐蚀速率及形貌。结果表明：在50℃的循环废酸中,316L和HastelloyC合金均具有优异的耐蚀性,且耐蚀性相当;316L和HastelloyC合金的腐蚀速率均随循环废酸温度的升高而增加,316L合金的增加缓慢,HastelloyC合金的增加急剧;当温度由50℃升高到80℃时,循环废酸的氧化性增加,Mo含量较高的HastelloyC合金在循环废酸中不能形成完整、致密的钝化膜,从而使其耐蚀性急剧下降。     

Improvement of Intergranular Stress Corrosion Crack Susceptibility of Austenite Stainless Steel through Grain Boundary Engineering

Intergranular stress corrosion crack susceptibility of austenite stainless steel was evaluated through threepoint bending test conducted in high temperature water. The experimental results showed that the frequent and efficient introduction of low energy coincidence site lattice boundaries through grain boundary engineering resulted in an apparent improvement of the intergranular stress corrosion crack resistance of austenite stainless steel.     

Weld decay-resistant austenitic stainless steel by grain boundary engineering

This paper presents an example of grain boundary engineering (GBE) for improving intergranular-corrosion and weld-decay resistance of austenitic stainless steel. Transmission and scanning electron microscope (TEM and SEM) observations demonstrated that coincidence site lattice (CSL) boundaries possess strong resistance to intergranular precipitation and corrosion in weld decay region of a type 304 austenitic stainless steel weldment. A thermomechanical treatment for GBE was tried for improvement of intergranular corrosion resistance of the 304 austenitic stainless steel. The grain boundary character distribution (GBCD) was examined by orientation imaging microscopy (OIM). The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of CSL boundaries indicated a maximum at the small roll-reduction. The corrosion rate was much smaller in the thermomechanical-treated specimen than in the base material for long time sensitization. The optimum thermomechanical treatment introduced a high frequency of CSL boundaries and the clear discontinuity of corrosive random boundary network in the material, and resulted in the high intergranular corrosion resistance arresting the propagation of intergranular corrosion from the surface. The optimized 304 stainless steel showed an excellent resistance to weld decay during arc welding.     

S32750双相不锈钢相界与晶界特征对其力学性能和耐蚀性能的影响EI北大核心CSCD

通过固溶处理获得不同初始组织状态的S32750双相不锈钢样品,然后进行厚度压下量80%的冷轧变形和1050℃的退火处理,采用SEM-EBSD和XRD技术研究合金相界与晶界特征以及相组成分布情况,并利用拉伸实验、纳米压痕和双环电化学动电位再活化法(DL-EPR)分析不同初始状态样品的组织对力学性能与耐晶间腐蚀性能的影响规律。结果表明:高温固溶处理的合金样品经冷轧退火后晶粒细小均匀,两相分布接近1∶1,且相界占内界面(晶界+相界)比例较高,同相晶粒团簇程度最低,表现出优异的综合力学性能。合金样品经敏化处理后,σ相易沿α相晶界析出,高温固溶并经轧制退火后的样品中,由于α晶界比例较少且满足K-S取向关系的相界比例较高则又表现出良好的晶间腐蚀抗力。因此,通过适当的工艺来调控合金的相界与晶界分布可以实现材料强度和晶间腐蚀抗力的同步改善。     

Proton irradiation assisted localized corrosion and stress corrosion cracking in 304 nuclear grade stainless steel in simulated primary PWR water

Localized deformation and corrosion in irradiated 304 nuclear grade stainless steel in simulated primary water were investigated.The investigation was conducted by comparing the deformation structure,the oxide scale formed at the deformation structure,and their correlation with cracking.The results revealed that increasing the irradiation dose promoted localized corrosion at the slip step and grain boundary,which was primarily attributed to the strain concentration induced by enhanced localized deformation and depletion of Cr at grain boundary.Further,a synergic effect of the enhanced localized deformation and localized corrosion at the slip step and grain boundary caused a higher cracking susceptibility of the irradiated steel.     

Grain boundary engineering of 304 austenitic stainless steel by laser surface melting and annealing

In order to improve the intergranular corrosion resistance of 304 stainless steel, laser surface remelting experiments were conducted using a 2 kW continuous wave Nd: YAG laser. The grain boundary character distribution (GBCD) and microstructures of the materials were analyzed using EBSD, SEM and OM. The experimental results showed that combination of laser surface melting and annealing on 304 stainless steel resulted in a high frequency of twin boundaries and consequent discontinuity of random boundary network in the materials, which led to an improvement of resistance to intergranular corrosion. The maximum CSL density could reach 88.6% under optimal processing conditions: 1220 K and 28 h.     

热轧高Ni高强钢的表面晶界特征和电化学行为

采用EBSD技术和原子力显微镜(AFM)测试了10CrNi5Mo高强钢热轧态和热处理态试样的表面晶界分布特征和微观形貌, 用模拟海水全浸实验方法及电化学阻抗谱技术测试了10CrNi5Mo高强钢在模拟海水中的腐蚀行为。结果表明: 热轧态试样表面具有更高比例的小角度晶界, 经硝酸酒精腐蚀后热处理态试样表面腐蚀更为均匀, 粗糙度更小。进行模拟海水全浸实验时热轧态试样呈现出更好的耐腐蚀性能, 浸泡中期阻抗值增大, 表面腐蚀产物与基体结合更为紧密, 能保护基体防止其与溶液发生电化学反应。     

Grain boundary engineering of titanium-stabilized 321 austenitic stainless steel

Grain boundary engineering (GBE) primarily aims to prevent the initiation and propagation of intergranular degradation along grain boundaries by frequent introduction of coincidence site lattice (CSL) boundaries into the grain boundary networks in materials. It has been reported that GBE is effective to prevent intergranular corrosion due to sensitization in unstabilized 304 and 316 austenitic stainless steels, but the effect of GBE on intergranular corrosion in stabilized austenitic stainless steels has not been clarified. In this study, a twin-induced GBE utilizing optimized thermomechanical processing with small pre-strain and subsequent annealing was applied to introduce very high frequencies of CSL boundaries into a titanium-stabilized 321 austenitic stainless steel. The resulting steel showed much higher resistance to intergranular corrosion after sensitization subsequent to carbon re-dissolution heat treatment during the ferric sulfate–sulfuric acid test than the as-received one. The high CSL frequency resulted in a very low percolation probability of random boundary networks in the over-threshold region and remarkable suppression of intergranular corrosion during GBE.     

On the mechanism of intergranular stress corrosion cracking of sensitized stainless steel in tetrathionate solution

Intergranular stress corrosion cracking (SCC) mechanism in sensitized stainless steel (Type 304) was investigated experimentally. A tetra-thionic potassium (K₂S₄O₆) chemical solution was used to mimic polythionic acid SCC which the most aggressive SCC type. During the SCC test, the steel specimen was subjected to three-point bending with constant strain at room temperature, and simultaneous monitoring of acoustic emission and corrosion potential were employed to monitor SCC initiation and progression. At the early stage, transient phenomenon of local anodic dissolution was observed. Upon initiation of SCC, passivation film fracture and dissolution of metal at specimen surface take place. Through microscopic observation of SCC tip, it was found that the SCC tip advanced along the grain boundary with further mechanical loading. This suggested that the stress component plays a significant role of SCC propagation, in addition to the effect of the localized metal dissolution along Cr-depleted grain boundaries.