U-10Zr/Zr-4合金界面的微观结构及生长动力学研究（英文）

为研究U-Zr合金与Zr-4合金之间的相容性和扩散行为,采用真空热压扩散法制备U-10wt%Zr/Zr-4扩散偶,随后在高真空中580~1100℃高温热处理样品。采用扫描电镜和透射电镜分析检测扩散偶的界面微观结构和元素分布。系统研究了两种合金之间的相容性。δ-UZr_2层和厚约20nm的富铀层形成于热压扩散法制备的样品界面。测量了合金界面扩散系数常数和扩散激活能,分别为(4.23±0.63)×10~(-6)m~2/s和(160.73±1.67) kJ/mol。结果表明U-10wt%Zr/Zr-4扩散偶的扩散系数大于U-Zr合金的,特别是在低温段。     

锆合金包壳Cr涂层界面元素扩散行为研究进展

随着核反应堆向高燃耗和更长服役寿命方向发展,对包壳材料的安全可靠性提出了更高的要求。锆合金表面Cr涂层由于其优异的抗高温氧化性能、耐腐蚀性能以及与基体良好的兼容性,被认为是最有前景的耐事故涂层包壳材料。综述了近年来涂层Cr与基体Zr界面元素扩散行为的研究成果,重点介绍了Cr涂层不同状态下的界面结构及演变规律,包括沉积、退火、辐照、氧化等状态。总结了Cr的扩散、分布和金属间化合物Zr-Cr-(Fe)层的生长动力学模型,归纳了界面扩散对涂层结构及性能的不利影响。扩散阻挡层是一种抑制涂层与基体互扩散的有效结构,介绍了阻挡层设计制备原则以及现有的和潜在的金属或陶瓷阻挡层材料,分析了2类典型阻挡层的优缺点。金属阻挡层能抑制Cr的扩散并延迟Cr-Zr共晶反应,但需要考虑中子经济性;虽然陶瓷阻挡层阻隔元素扩散的性能优异,但由于其与锆合金力学性能和热膨胀系数的差异明显,易产生微裂纹,需要考虑其抗裂性。最后提出了采用实验与分子动力学等相结合的多尺度研究方法开展界面研究,同时指出了目前研究工作中亟待解决的关键问题,这为后续的锆合金表面耐事故涂层研究与开发提供了重要参考。     

Zr-0.8Sn-1Nb-0.3Fe合金的微观组织研究

本文采用光学显微镜和透射电子显微镜对两种制备工艺的Zr-0.8Sn-1Nb-0.3Fe锆合金进行了微观组织分析与表征。实验结果表明增加冷轧次数与退火过程会导致锆合金的晶粒尺寸变大和不均匀化,平均尺寸从3.9μm长大到6.0μm;且析出相的尺寸变大、弥散程度降低,平均尺寸从74.6nm长大至89.6nm。增加冷轧次数与退火过程会使基体中的Nb进一步析出,析出相中Nb/Fe比值增加,平均值从1.17增加至1.39。两种锆合金中的析出相主要为面心立方结构的(Zr,Nb)2Fe化合物,Nb/Fe比值较低,尺寸较大。而在增加冷轧次数与退火过程的锆合金中还观察到少量密排六方结构的Zr(Nb,Fe)2析出相,Nb/Fe比值较高,尺寸较小。     

Zr-4合金与模具钢的界面换热行为研究

界面换热系数是锆合金塑性成形模拟的重要边界条件之一。本文测定了界面有、无玻璃润滑剂条件下Zr-4合金和H13模具钢的界面接触温度随接触时间的变化曲线,在此基础上分析了界面换热特征,获得了界面换热系数随初始界面温度变化的函数式。结果表明,玻璃润滑剂可有效减缓Zr-4合金与H13钢的界面传热,当Zr-4合金和H13钢的初始界面温度分别为700℃和470℃时,有玻璃润滑剂时Zr合金表面温度达到稳定的时间约为16.3s,该时间段内相应的界面换热系数随实验时间的延长由226 W/( m₂?℃)增大到2166 W/( m₂?℃),无润滑剂时Zr合金表面温度达到稳定的时间约为7.7s,该时间段内界面换热系数由250 W/( m₂?℃)增大到2700 W/( m₂?℃)。采用本文确定的换热系数随温度变化的关系式进行热交换模拟可以获得较高的模拟精度,模拟与实验结果的最大误差约为4.5%。     

Cr涂层对Zr-1Nb合金包壳微动磨损行为的影响

采用三维白光干涉仪、扫描电子显微镜、能谱仪等表征技术对比研究Cr涂层Zr-1Nb合金包壳和Zr-1Nb合金包壳与格架在模拟压水堆一回路水环境下的微动磨损行为及损伤机制。结果表明,Cr涂层显著提高Zr-1Nb合金包壳的抗微动磨损性能。此外,对磨副为刚凸时,Zr-1Nb合金包壳微动磨损机制以磨粒磨损和剥层磨损为主,而Cr涂层Zr-1Nb合金包壳由于表面硬度较高,且表面形成具有保护作用的三体层,其损伤机制以黏着磨损和材料单向转移为主。对磨副为弹簧时,Zr-1Nb合金包壳微动磨损机制主要为剥层和黏着磨损,Cr涂层Zr-1Nb合金包壳主要为磨粒磨损。     

In-Sn熔体合金与CuZr基块状非晶合金界面生长动力学(英文)

研究In-Sn熔体合金与Cu40Zr44Al8Ag8块状非晶合金的界面生长动力学。通过扫描电镜和能谱对时效的样品进行分析,发现界面层由Zr、Cu和Sn组成。在时效温度区间,扩散机制是反应速度的控制步骤,且时间指数值近似为0.5。计算得到的反应激活能为98.35kJ/mol。     

Zr-4合金表面耐事故Cr涂层制备及组织性能研究

在锆合金包壳表面制备保护性涂层材料能够改善现行核燃料组件的服役性能,延缓在＞1200℃高温蒸汽下的锆水反应,提升其在反应堆失水事故下的容错能力。因此,涂层技术也被列为耐事故核反应堆设计和研究的短期规划。本文采用等离子增强物理气相复合沉积技术,在Zr-4合金表面制备了Cr复合涂层,并专门针对涂层与基体的界面进行了离子的轰击注入强化。结合锆合金包壳的实际使用工况,设计试验方法,评价表征了涂层体系的各项性能及其对锆合金基体的影响。高温蒸汽加速腐蚀试验表明,相比于无涂层Zr-4基体试样,Cr涂层明显阻碍了氧向Zr-4基体内部的扩散,并有效抑制了基体内部有害氢化物的生成。在模拟事故的＞1000℃的高温热冲击条件下,相比于无涂层基体表面较厚氧化物生成的现象,涂层样品并未出现脱落,基体也并未出现氧化腐蚀。拉伸及内压爆破测试表明,样品表面Cr涂层表现出与基体较好的附着力,未出现沿破裂界面的脱落,也未影响Zr-4基体的拉伸及室温爆破性能。可以认为,Zr-4合金表面Cr涂层是理想的耐事故涂层材料之一。     

酸洗工艺对Zr-4合金微动磨蚀行为的影响

在高温高压水环境中对压水堆燃料包壳Zr-4合金开展了微动磨蚀试验.利用三维白光干涉仪、光学显微镜、扫描电镜、能谱等分析了微动磨蚀试验后试样的三维轮廓、表面形貌和化学成分.结果表明:酸洗和普洗Zr-4合金的磨蚀系数分别为6.26×10-16 Pa-1和3.3×10-16 Pa-1;Zr-4合金的损伤机制主要为黏着磨蚀损伤...     

PdY/FeCrAl复合丝材的界面结构和扩散

制备了一种以 FeCrAl 合金为芯层、PdY 合金为覆层的复合材料丝材。用金相显微镜、X射线衍射仪和电子探针仪观察、分析了复合丝材在850℃大气退火不同时间后的界面结构和界面扩散。由于各元素的扩散和相互作用,界面层中有3种新相生成,新相对各元素的界面扩散有很大的影响。Fe、Cr、Al、Pd的扩散层深度ξ和退火时间t遵循如下关系：ξ=k?3 t (k是元素的扩散速度常数)。     

Zr-4合金包壳管维氏硬度与强度关系研究

硬度反映了金属材料在局部范围内抵抗外物压入的能力,其与强度之间存在一定的内在联系。通过室温拉伸和维氏硬度试验,研究了不同状态Zr-4合金包壳管维氏硬度与强度之间的关系,通过最小二乘法建立了维氏硬度与抗拉强度、屈服强度之间的回归方程,分别为y_1=5.764x–544.215(R~2=0.997),y_2=5.743x–647.90(R~2=0.998）,并分析了回归方程的拟合效果。研究表明,Zr-4合金包壳管强度与维氏硬度的相关性极强,二者之间存在较强的正相关性。基于所建立的显微硬度与强度的回归方程,确定了Zr-4合金包壳管冷轧过程中维氏硬度与抗拉强度、屈服强度之间的关系。使用含有初始屈服应力的刚塑性指数硬化数学模型,建立了Zr-4合金包壳管皮尔格两辊冷轧工作锥强度与当量变形量之间的关系式,分别为σ_s=297.37+353.13ε_(Hz)~(0.34),σ_b=453.57+306.47ε_(Hz)~(0.44),相关系数分别为0.96和0.97。     

Microstructural characterization of the Al/Cu/steel diffusion bonded joint

A vacuum hot-pressed diffusion method was used to prepare an Al/Cu/steel composite with a gradient structure. The Al/Cu interface was investigated layer by layer by means of scanning electron microscopy, energy dispersive X-ray spectrometry, electron probe microanalysis, and Vickers microhardness. The results show that two kinds of intermetallic compounds, Cu₉Al₄ adjacent to the Cu side and CuAl₂ adjacent to the Al side, are formed in the interface of Al/Cu. The conductivity is 0.369 mS/cm in the intermetallic compound with a thickness of 3.5 μm, higher than that of the intermetallic compound with a thickness of 23 μm, in which the conductivity is 0.242 mS/cm.     

TC4/Cu/ZQSn10-2-3扩散连接接头微观分析

TC4/ZQSn10-2-3直接扩散连接时,结合区由于生成CuSn_3Ti_5,Cu_3Ti等金属间化合物及集聚的Pb质点,接头强度不高(τ_(max)=102 MPa),断口为脆性断口,并发生在靠近ZQSsn10-2-3侧;填加金属中间层铜时,TC4/Cu/ZQSn10-2-3扩散连接接头强度获得显著提高(τ_(max)=196 MPa),这主要是铜中间层有效地抑制了Sn,Pb等元素向TC4侧的扩散,减少CuSn_3Ti_5,Cu_3 Ti等金属间化合物相生成,断口具有一定塑性;TC4/Cu,ZQSn10-2-3最佳扩散连接参数为:连接温度830℃,连接压力10 MPa,连接时间30 min.

Abstract：

The experimental investigation on the diffusion bonding of TC4 to ZQSn10-2-3 was carried out in vacuum. CuSn_3 Ti_5, Cu_3 Ti and rich-Pb layer were formed at the interface zone. The maximum joint strength was 102 MPa. Brittle fracture was explored after shear test, and occurred proximity to ZQSn10-2-3 side. Using copper as the interlayer, element Sn and Pb can be avoid diffusing from ZQSn10-2-3 to TC4. Then there were little CuSn_3Ti_5 in the interface. Fracture had certain plasticity, and the maximum strength of joint was 196 MPa. The optimum bonding parameters were: bonding temperature T = 830 ℃ , bonding pressure p = 10 MPa and bonding time t = 30 min.     

Thermal property characterization of a Ti–4 wt.%Nb–4 wt.%Zr alloy using drop and differential scanning calorimetry

The thermal properties of Ti–4 wt.%Nb–4 wt.%Zr alloy, namely the enthalpy increment and heat capacity have been characterized as a function of temperature using drop and differential scanning calorimetry, respectively. The measured data clearly attested to the presence of a phase change from α (hcp) to β (bcc) phase at about 1100 ± 5 K. In fact, the alloy exhibited a transformation domain in the temperature interval 1100–1170 K. The enthalpy associated with the α → β phase change is estimated to be about 73 (±5%) J g⁻¹. The jump in the specific heat at the transformation temperature is 1714 (±7%) J kg⁻¹ K⁻¹. The drop and differential scanning calorimetry results are consolidated to obtain the first experimental data on the thermodynamic quantities of this alloy.     

Improvement of the hydrogen-storage kinetics of Mg by reactive mechanical grinding with 10 wt.% Fe2O3 and 5 wt.% Ni

The addition of Fe₂O₃ to Mg is believed to be able to increase the hydriding rate of Mg, and the addition of Ni is thought to be able to increase the hydriding and dehydriding rates of Mg. A sample Mg-(10wt.%Fe₂O₃, 5 wt.%Ni) was prepared by mechanical grinding under H₂ (reactive mechanical grinding). The as-milled sample absorbed 4.61 wt.% of hydrogen at 593 K under 12 bar H₂ for 60 min. Its activation was accomplished after two hydriding-dehydriding cycles. The activated sample absorbed 4.59 wt.% of hydrogen at 593 K under 12 bar H₂ for 60 min, and desorbed 3.83 wt.% hydrogen at 593 K under 1.0 bar H₂ for 60 min. The activated Mg-(10wt.%Fe₂O₃, 5 wt.%Ni) had a slightly higher hydriding rate at the beginning of the hydriding reaction but a much higher dehydriding rate compared with the activated Mg-10 wt.%Fe₂O₃. prepared via spray conversion. After hydriding-dehydriding cycling, Fe₂O₃ was reduced, Mg₂Ni was formed by the reaction of Mg with Ni, and a small fraction of Mg was oxidized.     

热压工艺对SiCf/Ti复合材料界面反应层生长影响的数值模拟

提出一个热-力-扩散-反应强耦合相场模型来研究热压烧结制备工艺对连续碳化硅纤维增强钛基复合材料中金属间化合物生长规律的影响。模拟结果表明,在两种不同温度下各个界面反应层(Ti₃SiC₂/Ti₅Si₃C_x/Ti₅Si₃C_x+TiC/TiC)的厚度生长与试验值吻合较好。增大外加压力能促进界面层厚度的生长,但对其中抗拉强度最低的Ti₅Si₃层的生长起显著的抑制作用,同时使各界面反应层由周向拉应力状态逐渐转变为压应力。温度的升高使断裂韧度最大的Ti₃SiC₂层厚度增大,但也使总界面层和Ti₅Si₃层的厚度增加。因此,在制备工艺上适当增加压力并选择合适的温度,得到厚度适宜的界面反应层的同时,尽可能使Ti₅Si₃层变薄和Ti₃Si...     

Effect of alternative magnetic field on the diffusion layer growth in Al／Zn couple

The influence of an alternative magnetic field on the growth of the diffusion layer in A1-Zn diffusion couple was studied. The thickness of the diffusion layer was examined. The results show that the alternative magnetic field increases the thickness of the diffusion layer and the effect increases with the intensity and frequency of the alternative magnetic field increasing. The growth of the diffusion layer obeys the parabolic rate law and the growth rate increases with the application of the alternative magnetic field. This growth rate change is manifested through a change in the frequency factor ko and not through a change in the activation energy Q. The frequency factor k0 for the diffusion layer growth with the alternative magnetic field is 5.03cm^2/s and the one without the magnetic field is 3.84cm^2/s.     

电子束焊接QCr0.8/TC4焊缝反应层结构及成长分析

QCr0.8/TC4偏铜电子束焊接焊缝由熔合区及反应层组成,其中反应层的组织结构、相组成和反应程度是影响接头抗拉强度的主要因素.参考扩散理论,利用Fick第一定律计算了稳态扩散时Cu,Ti两种组元在界面处的扩散通量比.反应层中优先生成CuTi化合物,其在反应层中为连续生成及分布.通过能谱分析得出反应层的组成依次为Cu CuxTi区,CuTi基固溶体区.其中CuxTi为多种化合物的混合,如Cu4Ti,Cu3Ti,Cu2Ti等.由于电子束焊接接头冷却速度极快,TC4侧靠近熔合线处来不及生成第二相化合物,因此反应层处形成的连续金属间化合物CuTi层使该处变得硬脆且残余应力较大,成为影响接头力学性能的主要因素.     

硝酸根离子对U-0.79Ti合金腐蚀行为的抑制作用

采用电化学方法研究了硝酸根离子(NO3-)对U-0.79Ti合金在0.01mol/LNa Cl溶液中腐蚀的抑制作用。实验证明,NO3-对U-0.79Ti合金在含氯离子(Cl-)溶液中的腐蚀具有抑制作用,且与NO3-浓度密切相关。当NO3-与Cl-浓度比大于0.1时,NO3-能够有效抑制U-0.79Ti合金点蚀的发生;而低于这个比例时,NO3-对U-0.79Ti合金的腐蚀行为几乎无影响。从电化学过程来看,加入NO3-能够降低浓差极化并增大极限扩散电流密度。同时,NO3-能够降低氧化膜的阳极活性溶解速度,提高U-0.79Ti合金的点蚀电位。表面划痕实验则表明,NO3-的抑制作用很可能缘于其优先于Cl-在表面缺陷处吸附,阻碍了Cl-的点蚀成核。     

Microstructure characterization of as-fabricated and 475 °C annealed U-7 wt.% Mo dispersion fuel in Al-Si alloy matrix

High-density uranium (U) alloys with an increased concentration of U are being examined for the development of research and test reactors with low enriched metallic fuels. The U-Mo fuel alloy dispersed in Al-Si alloy has attracted particular interest for this application. This paper reports our detailed characterization results of as-fabricated and annealed (475 °C for 4 h) U-Mo dispersion fuels in Al-Si matrix with a Si concentration of 2 and 5 wt.%, named as “As2Si”, “As5Si”, “An2Si”, “An5Si” accordingly. Techniques employed for the characterization include scanning electron microscopy and transmission electron microscopy with specimen prepared by focused ion beam in situ lift-out. Fuel plates with Al-5 wt.% Si matrix consistently yielded thicker interaction layers developed between U-Mo particles and Al-Si matrix, than those with Al-2 wt.% Si matrix, given the same processing parameters. A single layer of interaction zone was observed in as-fabricated samples (i.e., “As2Si”, “As5Si”), and this layer mainly consisted of U₃Si₃Al₂ phase. The annealed samples contained a two-layered interaction zone, with a Si-rich layer near the U-Mo side, and an Al-rich layer near the Al-Si matrix side. The U₃Si₅ appeared as the main phase in the Si-rich layer in “An2Si” sample, while both U₃Si₅ and U₃Si₃Al₂ were identified in sample “An5Si”. The Al-rich layer in sample “An2Si” was amorphous, whereas that in sample “An5Si” mostly consisted of crystalline U(Al,Si)₃, along with a small fraction of U(Al,Si)₄ and U₆Mo₄Al₄₃ phases. The influence of Si on the diffusion and reaction in the development of interaction layers in U(Mo)/Al(Si) is discussed in the light of growth-controlling mechanisms and irradiation performance.     

激光原位制备TiB/Ti-6Al-4V复合涂层中TiB管状结构的形成机制

利用透射电镜(TEM)、电子背散射衍射(EBSD)技术,系统观察、分析了激光原位制备TiB/Ti-6Al-4V复合涂层中TiB生长形态、分布以及晶体学取向,以探讨管状结构TiB的形成机制。结果表明:涂层中TiB的形态主要有棒状和针状2种,受控于生长时间和元素浓度2个因素。棒状TiB形核于过共晶成分区域,针状TiB形核于共晶成分和亚共晶成分区域。当TiB的直径和生长速度之积超过临界值时,(010)_(B27)和(001)_(Bf)晶面的生长将不再稳定。界面边缘区域更易获得硼原子,生长速度快于中心区域,而边缘区域对硼元素的消耗进一步抑制了中心区域的生长,从而产生了管状结构。随着TiB直径的增加,管状结构出现的概率增加。