WO2020142862A1 - 一种观察锆合金纳米第二相的电化学腐蚀方法 - Google Patents

一种观察锆合金纳米第二相的电化学腐蚀方法 Download PDF

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WO2020142862A1
WO2020142862A1 PCT/CN2019/000249 CN2019000249W WO2020142862A1 WO 2020142862 A1 WO2020142862 A1 WO 2020142862A1 CN 2019000249 W CN2019000249 W CN 2019000249W WO 2020142862 A1 WO2020142862 A1 WO 2020142862A1
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electrochemical corrosion
phase
sample
zirconium alloy
electrochemical
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PCT/CN2019/000249
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French (fr)
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李阁平
韩福洲
刘承泽
袁福森
张英东
郭文斌
穆罕默德·阿里
顾恒飞
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中国科学院金属研究所
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/2202—Preparing specimens therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
    • G01N23/2251—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident electron beams, e.g. scanning electron microscopy [SEM]

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  • the invention relates to the field of nanometer second phase of zirconium alloy material and the field of metallographic electrochemical corrosion, and specifically provides an electrochemical corrosion method for observing the nanometer second phase in zirconium alloy.
  • the zirconium alloy has a lower thermal neutron absorption cross section, which can ensure that there are enough thermal neutrons in the nuclear reactor to maintain the normal operation of the reactor.
  • the zirconium alloy has good corrosion resistance and mechanical properties, as well as good Processability, so it is widely used in nuclear reactor structural materials, such as nuclear reactor cladding materials, end plugs and so on.
  • the chemical corrosion method is commonly used to obtain the microstructure characteristics of zirconium alloy, but the corrosion rate is difficult to control by chemical corrosion method.
  • the corrosion rate is difficult to control by chemical corrosion method.
  • due to the complexity and difference of the second phase structure in the zirconium alloy there has not yet been found a general corrosion agent that can The second phase morphology and distribution characteristics of all zirconium alloys are shown, which has caused great trouble to the relevant scientific researchers. If a suitable corrosive agent or corrosion method can be found, it will play an important role in promoting the research on the second phase of the nanoscale zirconium alloy.
  • the purpose of the present invention is to provide an electrochemical corrosion method that can accurately and clearly display the nano second phase in the zirconium alloy, so as to achieve the purpose of observing and counting the second phase in the zirconium alloy under a scanning electron microscope.
  • the method is simple to operate, and can accurately, quickly and clearly display the morphological characteristics, size and distribution characteristics of the nano-sized second phase in the zirconium alloy, which solves the existing TEM technology in the preparation of the second phase of the zirconium alloy nano sample Problems of complexity, difficulty in operation, and limitations of observation.
  • the electrochemical etchant consists of 8-12% perchloric acid and 88-92% of other solvents (most preferably 10% perchloric acid + 90% other solvents), the other solvents are methanol, ethanol , One or more of ethylene glycol monobutyl ether and n-propanol; after preparing perchloric acid in proportion, place other solvents in the beaker in the shade, then slowly add perchloric acid and stir with a glass rod Until completely dissolved;
  • Portable electrochemical corrosion device includes DC power supply, magnetic stirrer, stainless steel sheet, thermometer, corrosive agent, wire and liquid nitrogen; one end of the wire is connected to the stainless steel sheet and placed on the side of the beaker, the other end of the wire is connected to the negative pole of the DC power supply, and the positive pole of the DC power supply passes through the wire Connect the sample to be corroded with tweezers;
  • the zirconium alloy sample is used as the anode, and the stainless steel sheet is used as the cathode.
  • the sample is clamped with tweezers and placed in the electrochemical corrosive agent, and the surface of the zirconium alloy sample is parallel to the stainless steel sheet.
  • the power supply voltage is controlled at 50-60V, when the electrochemical corrosion current is 0.10A-0.60A, stop the electrochemical corrosion, the corresponding electrochemical corrosion time It has a positive correlation with the set corrosion termination current;
  • step (1) the preliminary treatment method of the sample is: after the zirconium alloy sample to be corroded is polished on 150#, 320#, 800#, and 2000# sandpaper in sequence, the nano-SiO 2 suspension is used for mechanical polishing , Until the sample is bright mirror surface.
  • the electrochemical etchant is preferably one of the following five ratios:
  • step (4) the distance between the surface of the sample to be corroded and the stainless steel sheet is 10mm; the starting temperature of electrochemical corrosion is -120°C ⁇ -100°C, the ending current of electrochemical corrosion is 0.1 ⁇ 0.3A; the magnetic stirrer is located At the bottom of the electrochemical corrosive, adjust the magnetic stirrer, so that the rotor drives the electrochemical corrosive to form a vortex that penetrates up and down, removing the corrosion products on the surface of the sample.
  • the electrochemical corrosive agent in the present invention is a solution prepared strictly according to the ratio.
  • Perchloric acid itself does not react with the zirconium alloy and the second phase.
  • the presentation process of the nano-second phase in the zirconium alloy is actually an electrochemical reaction process At this time, the perchloric acid solution participates in the reaction as an electrolyte.
  • the physicochemical properties of different constituent phases and phase interfaces are different, and they have different free energies.
  • various nanosecond phases and matrix phases in the alloy will exhibit different electrode potentials, thus forming many microbatteries.
  • the lower potential part is the anode of the microbattery, which dissolves faster and dissolves.
  • the structure of the second phase in the zirconium alloy is more complicated than that of the zirconium alloy matrix. Therefore, in the process of electrochemical corrosion, the zirconium alloy matrix and the interface between the second phase and the matrix are preferentially corroded.
  • the second phase in the zirconium alloy The matrix around the phase is gradually corroded, so as long as the relevant parameters of electrochemical corrosion are strictly controlled, the second phase morphology of the zirconium alloy can be well presented.
  • the role of other solvents in the electrochemical corrosion agent of the present invention is to act as a corrosion inhibitor to effectively slow down the electrochemical corrosion process of the zirconium alloy.
  • the electrochemical corrosion method used in the present invention is a method capable of observing the size, morphology and distribution of the second phase in the zirconium alloy under a scanning electron microscope, and the reagents used are conventional chemical reagents, and the preparation method is simple , Convenient operation;
  • the present invention can prepare large-scale bright metallographic samples at one time for the observation of the second phase of zirconium alloy and statistical related research. Compared with the use of transmission electron microscopy to calculate the size, morphology and distribution of the second phase of zirconium alloy The traditional method of this method can more objectively reflect the distribution characteristics of the nano-second phase in the zirconium alloy;
  • the present invention has simple operation and high repeatability, and is suitable for electrochemical corrosion of the nano-second phase in zirconium alloys of various compositions and states.
  • Example 1 is the second phase morphology and its distribution diagram of cold-rolled and annealed Zircaloy-4 alloy in Example 1;
  • Example 2 is a microscopic feature morphology diagram of the second phase of Zircaloy-4 alloy at high magnification in Example 1;
  • Example 3 is a graph of the size and distribution density of the second phase obtained by statistically calculating the second phase in Example 1;
  • Example 4 is the second phase morphology and distribution diagram of the forged Zircaloy-2 alloy in Example 2;
  • Example 5 is a second phase backscattered electron morphology and element surface distribution diagram of the forged Zircaloy-2 alloy in Example 2;
  • Example 6 is a second phase morphology diagram of a high-magnification forged Zircaloy-2 alloy in Example 2
  • Example 7 is the second phase morphology and distribution diagram of the extruded N18 zirconium alloy in Example 3;
  • Example 8 is a morphology diagram of the second phase of the extruded N18 zirconium alloy in Example 3 at high magnification;
  • Example 9 is a morphology and distribution diagram of the second phase of the forged ZIRLO zirconium alloy in Example 4.
  • Example 10 is a morphology diagram of the forged ZIRLO zirconium alloy under high magnification in Example 4.
  • Example 11 is a secondary electron morphology diagram of the second phase distribution in the extruded N36 alloy of Example 5;
  • Example 12 is a morphology and distribution diagram of the second phase of Zircaloy-4 with poor corrosion effect in Example 1;
  • FIG. 13 is a morphology and distribution diagram of the second phase of Zircaloy-4 with poor corrosion effect in Example 1.
  • the concentration of perchloric acid used is 70-72 wt.%, and the DC power supply is 60V/1A.
  • the portable electrochemical corrosion device used in the present invention includes a DC power supply, a magnetic stirrer, a stainless steel sheet, a thermometer, an etchant, a wire, and liquid nitrogen; one end of the wire is connected to the stainless steel sheet and placed on one side of the beaker, and the other end of the wire is connected to the negative pole of the DC power supply.
  • the positive pole of the DC power supply is connected to the sample to be corroded by wires and tweezers;
  • Zircaloy-4 alloy (Zr-1.5wt%Sn-0.2wt%Fe-0.1wt%Cr) is currently the most widely used zirconium-tin zirconium alloy in nuclear reactors, which has excellent corrosion properties and good mechanical properties .
  • the matrix phase of Zircaloy-4 (hereinafter referred to as Zr-4) is the ⁇ -Zr phase with a close-packed hexagonal structure.
  • the common second phase morphology of the alloy is mainly spherical or ellipsoidal, and the size of the second phase is about Around 100nm.
  • the Zr-4 alloy in the cold rolled annealed state is used in this embodiment, and the specific implementation steps are as follows:
  • (1) Preparation of electrochemical corrosive agent First, measure 450ml of alcohol in a measuring cylinder and place it in a glass beaker. In a backlight environment at room temperature, measure 50ml of perchloric acid with a measuring cylinder and use a glass rod to drain slowly into the beaker In the preparation, the electrochemical corrosive is prepared and stored for use;
  • Electrochemical corrosion process Pour the electrochemical corrosion agent prepared in step (1) into the beaker of the electrochemical corrosion device, the stainless steel sheet connected to the negative electrode of the power supply is a 304 stainless steel sheet, and the polished Zr-4 alloy The sample is connected to the positive pole of the DC power supply. The polished observation surface of the sample faces the 304 stainless steel sheet, and keeps the sample parallel to the 304 stainless steel sheet. Add liquid nitrogen to the beaker to lower the temperature so that the initial temperature is -120°C, turn on the DC power supply and magnetic stirrer, and set the termination electrochemical corrosion current to 0.60A;
  • Zircaloy-2 is used in the forged state, and its nominal composition is Zr-1.5Sn-0.1Fe-0.1Cr-0.05Ni (wt%).
  • the alloy is a commercial zirconium alloy, mainly used in the field of nuclear reactor cladding.
  • the steps of the electrochemical corrosion process of the second phase of the forged Zircaloy-2 alloy are as follows:
  • Electrochemical corrosion process Pour the electrochemical corrosion agent prepared in step (1) into the beaker of the electrochemical corrosion device, the cathode material is 304 stainless steel sheet, and connect the polished Zircaloy-2 alloy sample to DC The positive pole of the power supply. The polished observation surface of the sample is directly facing the stainless steel sheet, and the sample is placed in parallel with the stainless steel sheet into the electrochemical corrosive agent. Add liquid nitrogen to the electrochemical corrosion agent to reduce the temperature to -90°C, turn on the magnetic stirrer and DC power supply, and set the termination electrochemical corrosion current to 0.50A;
  • the shape of the second phase in the alloy is mainly round or elliptical. Under the action of micro current, the interface between the second phase and the substrate is preferentially corroded, thus showing the typical zirconium.
  • the second phase of the alloy in which the interface between the second phase and the substrate shown by the arrow has been corroded, the second phase exhibits a clear morphology because it is difficult to corrode.
  • N18 (Zr-1Sn-0.3Nb-0.3Fe-0.1Cr) is a new type of zirconium alloy independently developed by my country. This embodiment mainly corrodes the second phase of the extruded N18 alloy. The main steps are as follows:
  • Electrochemical corrosion process Pour the electrochemical corrosion agent prepared in step (1) into the beaker of the electrochemical corrosion device, the cathode material is 304 stainless steel sheet, and connect the polished N18 zirconium alloy sample to the DC power supply The positive pole. The polished observation surface of the sample is directly facing the stainless steel sheet, and the sample is placed in parallel with the stainless steel sheet into the electrochemical corrosive. Add liquid nitrogen to the electrochemical corrosion agent to reduce the temperature to -100°C, turn on the magnetic stirrer and DC power supply, and set the electrochemical corrosion termination current to 0.4A;
  • Example 1 Forged ZIRLO zirconium alloy, the nominal composition of which is Zr-1.0Nb-1.0Sn-0.1Fe (wt%), the configuration process of the second phase electrochemical etchant is as in Example 1, the specific electrochemical corrosion steps are as follows:
  • electrochemical corrosion agent take 40ml of perchloric acid solution, 300ml of methanol solution, 100ml of ethanol and 40ml of ethylene glycol monobutyl ether to prepare electrochemical corrosion agent;
  • Electrochemical corrosion process Pour the electrochemical corrosion agent prepared in step (1) into the beaker, the cathode material is 304 stainless steel sheet, and connect the polished ZIRLO zirconium alloy sample to the positive electrode of the DC power supply.
  • the polished observation surface of the sample faces the stainless steel sheet, and the sample is placed in parallel with the stainless steel sheet into the electrochemical corrosive agent.
  • the nominal composition of extruded N36 alloy is (Zr-1.0wt%Sn-1.0wt%Nb-0.3wt%Fe).
  • the electrochemical corrosion steps of the second phase in N36 alloy are as follows:
  • Electrochemical corrosion process Pour the electrochemical corrosion agent into the beaker, the cathode material is 304 stainless steel sheet, and connect the polished N36 zirconium alloy sample to the positive electrode of the DC power supply.
  • the polished observation surface of the sample is directly facing the stainless steel sheet, and the sample is placed in parallel with the stainless steel sheet into the electrochemical corrosive.
  • the corrosion effect of the second phase of the zirconium alloy nanometer will all affect the corrosion effect of the second phase of the zirconium alloy nanometer, so the corrosion parameters must be strictly controlled in the test to achieve the best corrosion effect.
  • the corrosion current if the corrosion current is too low or too high, the corrosion effect may be poor.
  • the electrochemical corrosion current of the annealed Zr-4 alloy in Example 1 is 0.05A and 0.8A, respectively.
  • the etched samples were observed under a scanning electron microscope, and the morphology of the second phase in the resulting alloy is shown in Figure 12 and Figure 13, respectively.
  • the termination current is too low, as shown in Fig.
  • the morphological profile of the second phase can be observed, but its interface with the second phase is very unclear, and only a very small amount of the interface between the second phase and the matrix is Under the action of current, most of the second phases have not been corroded, so the size of the second phase statistically obtained in this case will definitely deviate from the actual situation; but when the corrosion termination current is too large, the nanometer The difference between the corrosion of the interface of the second phase and the substrate is insignificant compared to the difference in corrosion rate caused by the anisotropy of the substrate. In addition, under the action of a large current, the corrosion rate of the alloy is particularly fast. The two phases cannot be presented at all.

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Abstract

一种能够准确、清晰显示锆合金中纳米第二相的电化学腐蚀方法，以达到在扫描电子显微镜下观察、统计锆合金中第二相的目的。该方法采用特殊的电化学腐蚀剂，以锆合金试样作为阳极，不锈钢片作为阴极，采用液氮进行降温后进行电化学腐蚀，最终可在扫描电子显微镜下观察第二相。该方法操作简单，可以准确、快速、清晰的显示锆合金中纳米尺寸第二相的形貌特征、尺寸大小以及分布特征，解决了现有TEM技术在锆合金纳米第二相研究上存在制样复杂、操作困难、观察局限性的问题。

Description

一种观察锆合金纳米第二相的电化学腐蚀方法 技术领域
本发明涉及锆合金材料纳米第二相领域以及金相电化学腐蚀领域，具体提供一种用于观察锆合金中纳米第二相的电化学腐蚀方法。
背景技术
锆合金具有较低的热中子吸收截面，能够保证原子能反应堆中有足够的热中子数量以维持反应堆正常运转，另外锆合金还有具有良好的耐腐蚀性能和机械性能，以及很好的可加工性，因此其被广泛应用于核反应堆的结构材料，如核反应堆的包壳材料、端塞等。随着经济的发展，人们对于核材料的安全可靠性提出了越来越高的要求，于是各个国家通过调整合金元素成分以改变合金的显微组织，并研究开发了各自的新锆合金，如法国的M5合金、美国的ZIRLO合金和前苏联的E110和E635锆合金、以及我国生产的N18和N36锆合金。研究证实，改变合金成分对合金显微组织和性能都有很大的影响，这主要是由于成分改变导致锆合金中的第二相的形貌、结构以及分布改变。锆合金中第二相形貌、尺寸和分布特征的观察分析，对于合金的成分设计及其在服役过程中性能的保证具有重要的指导意义。目前，相关科研工作者主要是采用透射电子显微镜，研究锆合金中的第二相。但是，采用透射电子显微镜进行相关研究时，不仅制样过程十分复杂，仪器操作要求高，而且更重要是由于透射电子显微镜技术观察的局限性，试验根本无法获得锆合金中第二相的宏观分布特征。
目前，常用化学腐蚀的方法获得锆合金组织特征，但是化学腐蚀的方法其腐蚀速度难以控制；另外，由于锆合金中第二相结构的复杂性和差异性，目前尚未找到一种通用的腐蚀剂能够显现所有锆合金中的第二相形貌及分布特征，这就给相关的科研工作者造成了很大的困扰。如果能够找到一种合适的腐蚀剂 或者腐蚀方法，将对锆合金纳米尺寸第二相相关方面的研究起到重要的推动作用。
发明内容
本发明的目的是提供一种能够准确、清晰显示锆合金中纳米第二相的电化学腐蚀方法，以达到在扫描电子显微镜下观察、统计锆合金中第二相的目的。该方法操作简单，可以准确、快速、清晰的显示锆合金中纳米尺寸第二相的形貌特征、尺寸大小以及分布特征，解决了现有TEM技术在锆合金纳米第二相研究上存在制样复杂、操作困难、观察局限性的问题。
为了达到上述目的，本发明采用如下技术方案予以实现：
一种观察锆合金纳米第二相的电化学腐蚀方法，其特征在于，具体步骤如下：
(1)试样的前期处理：
将待腐蚀的锆合金试样打磨后进行机械抛光，直至试样呈光亮镜面；
(2)配制电化学腐蚀剂：
按体积百分比计，电化学腐蚀剂由8-12％的高氯酸和88-92％的其它溶剂组成(最优选为10％高氯酸+90％其它溶剂)，所述其它溶剂为甲醇、乙醇、乙二醇单丁醚、正丙醇之一种或多种；按比例准备好高氯酸后，在背阴处将其它溶剂置于烧杯中，然后缓缓加入高氯酸，并用玻璃棒搅拌至完全溶解；
(3)便携电化学腐蚀装置搭建：
便携电化学腐蚀装置包括直流电源、磁力搅拌器、不锈钢片、温度计、腐蚀剂、导线以及液氮；导线一端连接不锈钢片置于烧杯一侧，导线的另一端连接直流电源负极，直流电源正极通过导线和镊子连接待腐蚀试样；
(4)电化学腐蚀过程：
锆合金试样作为阳极，不锈钢片作为阴极，用镊子夹持试样放入电化学腐蚀剂中，并保持锆合金试样表面与不锈钢片平行正对；加入液氮降温处理，使得电化学腐蚀剂温度降至-120℃～-80℃，开启直流电源和磁力搅拌器，电源电压控制在50-60V，当电化学腐蚀电流为0.10A-0.60A时，停止电化学腐蚀，相应的电化学腐蚀时间与设置的腐蚀终止电流呈正相关性变化；
(5)后续处理及观察：当电流达到设置的电化学腐蚀终止电流值时，立即将试样从腐蚀剂中取出，用无水乙醇清洗干净后吹干保存，最后在扫描电子显微镜下观察第二相。
作为优选的技术方案：
步骤(1)中，试样的前期处理方法为：将待腐蚀的锆合金试样依次在150#、320#、800#、2000#砂纸上打磨后，采用纳米SiO 2悬浊液进行机械抛光，直至试样呈光亮镜面。
步骤(2)中，按体积百分比计，所述电化学腐蚀剂优选为以下五种配比之一：
(a)8-12％的高氯酸和88-92％的甲醇；
(b)8-12％的高氯酸和88-92％的乙醇；
(c)8-12％的高氯酸和88-92％的乙二醇单丁醚；
(d)8-12％的高氯酸和88-92％的正丙醇；
(e)8-12％的高氯酸+88-92％的甲醇+乙醇+乙二醇单丁醚+正丙醇。
步骤(4)中，待腐蚀试样表面和不锈钢片之间的距离为10mm；电化学腐蚀开始温度为-120℃～-100℃，电化学腐蚀终止电流为0.1～0.3A；磁力搅拌器位于电化学腐蚀剂的底部，调节磁力搅拌器，使得转子带动电化学腐蚀剂形成上 下贯穿的涡流，带去试样表面的腐蚀产物。
本发明中的电化学腐蚀剂，是严格按照配比配制的溶液，高氯酸本身不和锆合金及第二相反应，锆合金中纳米第二相的呈现过程实际上是一个电化学反应的过程，高氯酸溶液此时作为电解质参与反应。不同成分相以及相界面之间的物理化学性质不同，具有不同的自由能。当对其进行电化学腐蚀时，由于合金中各种纳米第二相与基体相会呈现不同的电极电位，从而形成许多的微电池，较低电位部分是微电池的阳极，溶解较快，溶解处呈现凹陷，锆合金中第二相的结构相对于锆合金基体更加复杂，所以电化学腐蚀的过程中，锆合金基体以及第二相与基体之间的界面优先被腐蚀，锆合金中第二相周围的基体被逐渐腐蚀，所以只要严格控制电化学腐蚀的相关参数，就可以很好的呈现锆合金中的第二相形貌特征。本发明电化学腐蚀剂中其它溶剂的作用是作为缓蚀剂，以有效减缓锆合金的电化学腐蚀过程。
本发明的技术优势在于：
(1)本发明采用的电化学腐蚀方法，是一种能够在扫描电子显微镜下观察锆合金中第二相大小、形貌及分布的方法，且采用的试剂均为常规化学试剂、配制方法简单、操作便捷；
(2)本发明可以一次性制备出大尺寸表面光亮的金相试样，用于锆合金第二相观察、统计相关研究，相对于采用透射电镜统计锆合金第二相尺寸、形貌和分布的传统方法，本方法能够更加客观的反应锆合金中纳米第二相的分布特征；
(3)采用本发明得到的锆合金第二相统计结果与采用透射电子显微镜结果高度一致，而且本发明中得到的锆合金中第二相形貌与基体之间的对比度较大，第二相轮廓十分清晰，对于小尺寸的锆合金第二相，适宜采用本发明在扫 描电子显微镜下对其进行观察；
(4)本发明操作简单、重复性高，适用于各种成分、各种状态锆合金中纳米第二相的电化学腐蚀。
附图说明
图1为实施例1中冷轧退火态Zircaloy-4合金第二相形貌及其分布图；
图2为实施例1中高放大倍数下Zircaloy-4合金第二相微观特征形貌图；
图3为实施例1中对第二相统计得出的第二相尺寸及分布密度图；
图4为实施例2中锻态Zircaloy-2合金第二相形貌及其分布图；
图5为实施例2中锻态Zircaloy-2合金第二相背散射电子形貌及元素面分布图；
图6为实施例2中高放大倍数的锻态Zircaloy-2合金第二相形貌图
图7为实施例3中挤压态N18锆合金第二相形貌及其分布图；；
图8为实施例3中挤压态N18锆合金第二相高放大倍数下形貌图；
图9为实施例4中锻造态ZIRLO锆合金第二相形貌及其分布图；
图10为实施例4中锻造态ZIRLO锆合金高放大倍数下形貌图；
图11为实施例5挤压态N36合金中第二相分布的二次电子形貌图；
图12为实施例1中腐蚀效果不佳的Zircaloy-4第二相形貌及分布图；
图13为实施例1中腐蚀效果不佳的Zircaloy-4第二相形貌及分布图。
具体实施方式
下面结合附图和具体实施方式对本发明进行进一步的说明，本实施例中，如未特殊说明，所用高氯酸的浓度为70-72wt.％，直流电源为60V/1A。
本发明采用的便携电化学腐蚀装置包括直流电源、磁力搅拌器、不锈钢片、温度计、腐蚀剂、导线以及液氮；其中导线一端连接不锈钢片置于烧杯一侧， 导线的另一端连接直流电源负极，直流电源正极通过导线和镊子连接待腐蚀试样；
实施例1：
Zircaloy-4合金(Zr-1.5wt％Sn-0.2wt％Fe-0.1wt％Cr)是目前核反应堆中应用最广泛的一种锆-锡系锆合金，其具有优异的腐蚀性能以及良好的力学性能。Zircaloy-4(以下简称为Zr-4)在室温下基体相为密排六方结构的α-Zr相，合金中常见的第二相形貌主要为球状或者椭球状，其第二相尺寸约为100nm左右。本实施例中使用的是冷轧退火态的Zr-4合金，具体的实施步骤如下：
(1)配制电化学腐蚀剂：首先用量筒量取450ml的酒精置于玻璃烧杯中，在室温下背光的环境下，用量筒量取50ml的高氯酸，并用玻璃棒引流缓缓倒入上述烧杯中，配制得到电化学腐蚀剂，保存待用；
(2)试样制备：待电化学腐蚀剂配置好以后，将待腐蚀的Zr-4合金依次经过150#、320#、800#、2000#水磨砂纸打磨后，再用纳米SiO 2悬浊液对其进行机械抛光，直到抛光面呈现镜面效果为止，然后依次用水和酒精对试样进行清洗，并吹干待用；
(3)电化学腐蚀过程：将步骤(1)中制备的电化学腐蚀剂倒入电化学腐蚀装置的烧杯中，与电源负极连接的不锈钢片为304不锈钢薄片，将已经抛光后的Zr-4合金试样连接到直流电源的正极。试样抛光观察面正对304不锈钢薄片，并保持试样与304不锈钢薄片平行。向烧杯中加入液氮降温，使其初始温度为-120℃，开启直流电源和磁力搅拌器，设置终止电化学腐蚀电流为0.60A；
(4)后续处理及观察：当电化学腐蚀电流达到0.60A时，立即关闭电源，并取下试样，用无水乙醇清洗试样并干燥。采用扫描电子显微镜观察采用本发明电化学腐蚀后的试样，其第二相宏观分布如图1所示，第二相典型的形貌特 征如图2所示，由于采用的终止电流偏大，第二相与基体界面已经被完全腐蚀，第二相脱落，呈现了原有第二相形貌及分布特征。图中的暗色衬度的圆形或者椭圆形区域即第二相具体的分布位置。
采集试样不同区域的第二相形貌的照片，然后利用相关软件对第二相尺寸和分布特征统计结果如图3所示，其结果与采用透射电子显微镜统计的结果基本一致。由此可知，采用本发明可以获得准确的锆合金第二相形貌、尺寸大小以及分布特征。
实施例2：
本实施例中使用的是锻态的Zircaloy-2其名义成分为Zr-1.5Sn-0.1Fe-0.1Cr-0.05Ni(wt％)。该合金是一种商用的锆合金，主要应用于核反应堆包壳领域。本实施例中，锻态Zircaloy-2合金第二相的电化学腐蚀过程步骤具体如下：
(1)配制电化学腐蚀剂：取50ml高氯酸溶液和450ml的甲醇溶液，按照发明内容步骤(1)中描述配制电化学腐蚀剂；
(2)试样制备：将待腐蚀的锻态Zircaloy-2合金依次经过150#、320#、800#、2000#水磨砂纸打磨后，再用纳米SiO 2悬浊液对其进行机械抛光，直到抛光面呈现镜面效果为止，然后依次用水和酒精对试样进行清洗，并吹干待用；
(3)电化学腐蚀过程：将步骤(1)中制备的电化学腐蚀剂倒入电化学腐蚀装置的烧杯中，阴极材料为304不锈钢薄片，将已经抛光后的Zircaloy-2合金试样连接到直流电源的正极。试样抛光观察面正对不锈钢薄片，并保持试样与不锈钢薄片平行放入到电化学腐蚀剂中。向电化学腐蚀剂中加入液氮降温，使其温度为-90℃，开启磁力搅拌器和直流电源，设置终止电化学腐蚀电流为 0.50A；
(4)后续处理及观察：当电化学腐蚀电流达到设置值(0.50A)时，立即取下试样，用无水乙醇清洗试样，并干燥。采用扫描电子显微镜观察腐蚀后的Zircaloy-2合金试样，其第二相分布的二次电子形貌如图4所示，图中黑色衬度的为合金中第二相的具体分布位置；第二相的背散射电子形貌及元素面分布如图5所示，由图可以清晰看出第二相位置处存在Fe、Cr元素富集；高放大倍数下，第二相形貌二次电子图像如图6所示，由图可以看出合金中第二相的形状主要为圆形或者椭圆型，在微电流的作用下，第二相与基体界面被优先腐蚀，从而呈现出典型的锆合金第二相，其中箭头所示的第二相与基体界面已经被腐蚀，第二相由于难以腐蚀，从而呈现出清晰的形貌。
实施例3：
N18(Zr-1Sn-0.3Nb-0.3Fe-0.1Cr)是我国自主研发的新型堆用锆合金。本实施例主要是对挤压态N18合金第二相的腐蚀，主要步骤如下：
(1)配制电化学腐蚀剂：取40ml高氯酸溶液、400ml乙醇和60ml甲醇，按照发明内容步骤(1)中描述配制电化学腐蚀剂；
(2)试样制备：将待腐蚀的N18锆合金依次经过150#、320#、800#、2000#水磨砂纸打磨后，再用纳米SiO 2悬浊液对其进行机械抛光，直到抛光面呈现镜面效果为止，然后依次用水和酒精对试样进行清洗，并吹干待用；
(3)电化学腐蚀过程：将步骤(1)中制备的电化学腐蚀剂倒入电化学腐蚀装置的烧杯中，阴极材料为304不锈钢薄片，将已经抛光后的N18锆合金试样连接到直流电源的正极。试样抛光观察面正对不锈钢薄片，并保持试样与不锈钢薄片平行放入到电化学腐蚀剂中。向电化学腐蚀剂中加入液氮降温，使其 温度为-100℃，开启磁力搅拌器和直流电源，设置电化学腐蚀终止电流为0.4A；
(4)后续处理及观察：腐蚀结束后，立即取下试样，用无水乙醇清洗试样，并干燥。采用扫描电子显微镜观察腐蚀后的N18锆合金试样，其第二相分布的背散射电子形貌如图7所示，图中暗色衬度的圆形或者椭圆形区域为合金中第二相的具体位置，高放大倍数下第二相形貌特征的二次电子图像如图8所示。
实施例4
锻造态ZIRLO锆合金，其名义成分为Zr-1.0Nb-1.0Sn-0.1Fe(wt％)，其第二相电化学腐蚀剂的配置过程如实施例1，具体电化学腐蚀步骤如下：
(1)配制电化学腐蚀剂：取40ml高氯酸溶液、300ml的甲醇溶液、100ml乙醇和40ml乙二醇单丁醚，配制电化学腐蚀剂；
(2)试样制备：电化学腐蚀剂配置好以后，将待腐蚀的ZIRLO锆合金依次经过150#、320#、800#、2000#水磨砂纸打磨后，再用纳米SiO 2悬浊液对其进行机械抛光，直到抛光面呈现镜面效果为止，然后依次用水和酒精对样品进行清洗，并吹干待用；
(3)电化学腐蚀过程：将步骤(1)制备的电化学腐蚀剂倒入烧杯中，阴极材料为304不锈钢薄片，将已经抛光后的ZIRLO锆合金试样连接到直流电源的正极。样品抛光观察面正对不锈钢薄片，并保持试样与不锈钢薄片平行放入到电化学腐蚀剂中。向电化学腐蚀剂中加入液氮降温，使其温度为-110℃，开启磁力搅拌器和直流电源，设置终止电化学腐蚀电流为0.30A；
(4)后续处理及观察：当电化学腐蚀电流值达到设置值0.3A时，立即取下试样，用无水乙醇清洗试样，并干燥。然后采用扫描电子显微镜观察腐蚀后的ZIRLO锆合金试样，其第二相典型二次电子形貌如图9所示(图中箭头所指 为第二相)，可以清晰的看出，第二相周围的基体在电流的作用下已经被完全剥离，从而呈现第二相；其背散射电子图像如图10所示，可以看出第二相与基体之间的衬度明显，使用本发明方法可以很好的呈现第二相形貌。
实施例5
挤压态N36合金，其名义成分为(Zr-1.0wt％Sn-1.0wt％Nb-0.3wt％Fe)，N36合金中第二相的电化学腐蚀步骤如下：
(1)配制电化学腐蚀剂：取50ml高氯酸溶液、300ml乙醇和150ml正丙醇，按照发明内容步骤(1)中描述配制电化学腐蚀剂；
(2)试样制备：将待腐蚀的N36锆合金依次经过150#、320#、800#、2000#水磨砂纸打磨后，用纳米SiO 2悬浊液对其进行机械抛光，直到抛光面呈现镜面效果为止，然后依次用水和酒精对样品进行清洗，并吹干待用；
(3)电化学腐蚀过程：将电化学腐蚀剂倒入烧杯中，阴极材料为304不锈钢薄片，将已经抛光后的N36锆合金试样连接到直流电源的正极。试样抛光观察面正对不锈钢薄片，并保持试样与不锈钢薄片平行放入到电化学腐蚀剂中。向电化学腐蚀剂中加入液氮降温，使其温度为-120℃，开始电化学腐蚀时腐蚀电流为0.02A，设置终止电化学腐蚀电流为0.1A；
(4)后续处理及观察：当电化学腐蚀电流值达到设置值0.1A时，立即取下试样，用无水乙醇清洗试样，并干燥。然后采用扫描电子显微镜观察腐蚀后的N36锆合金试样，采用本发明方法腐蚀的N36锆合金，典型的第二相的二次电子形貌如图11所示(箭头所指为第二相)，从图11可以清晰看到纳米尺寸第二相与基体界面已经被优先腐蚀，从而呈现出第二相形貌。
实施例6
本发明中，温度、电化学腐蚀剂、腐蚀终止电流等都会对锆合金纳米第二相的腐蚀效果造成一定的影响，所以试验中必须要严格控制腐蚀参数以达到最佳的腐蚀效果。电化学腐蚀过程中，终止腐蚀电流过低或者过高，都可能使得腐蚀效果不佳。例如分别采用终止电化学腐蚀电流0.05A和0.8A，对实施例1中的退火态Zr-4合金进行电化学腐蚀。腐蚀后的试样在扫描电子显微镜下观察，得到的合金中第二相形貌分别如图12和图13所示。当终止电流过低时，如图11所示，可以观察到第二相的形貌轮廓，但是其与第二相的界面十分不清楚，而且只有极少量的第二相和基体的界面在微电流的作用下显现出来，大部分第二相并没有被腐蚀出来，所以这种情况下统计得到的第二相的尺寸与真实情况必定会有所偏差；但是当腐蚀终止电流过大时，纳米第二相的界面与基体腐蚀的差异相比基体的各向异性造成的腐蚀速度差异而言微不足道，另外在大电流的作用下，合金腐蚀速度特别快，电化学腐蚀后，锆合金中纳米第二相完全无法呈现。
上述实施例只为说明本发明的技术构思及特点，其目的在于让熟悉此项技术的人士能够了解本发明的内容并据以实施，并不能以此限制本发明的保护范围。凡根据本发明精神实质所作的等效变化或修饰，都应涵盖在本发明的保护范围之内。

Claims (8)

  1. 一种观察锆合金纳米第二相的电化学腐蚀方法，其特征在于，具体步骤如下：
    (1)试样的前期处理：
    将待腐蚀的锆合金试样打磨后进行机械抛光，直至试样呈光亮镜面；
    (2)配制电化学腐蚀剂：
    按体积百分比计，电化学腐蚀剂由8-12％的高氯酸和88-92％的其它溶剂组成，所述其它溶剂为甲醇、乙醇、乙二醇单丁醚、正丙醇之一种或多种；按比例准备好高氯酸后，在背阴处将其它溶剂置于烧杯中，然后缓缓加入高氯酸，并用玻璃棒搅拌至完全溶解；
    (3)便携电化学腐蚀装置搭建：
    便携电化学腐蚀装置包括直流电源、磁力搅拌器、不锈钢片、温度计、腐蚀剂、导线以及液氮；导线一端连接不锈钢片置于烧杯一侧，导线的另一端连接直流电源负极，直流电源正极通过导线和镊子连接待腐蚀试样；
    (4)电化学腐蚀过程：
    锆合金试样作为阳极，不锈钢片作为阴极，用镊子夹持试样放入电化学腐蚀剂中，并保持锆合金试样表面与不锈钢片平行正对；加入液氮降温处理，使得电化学腐蚀剂温度降至-120℃～-80℃，开启直流电源和磁力搅拌器，电源电压控制在50-60V，当电化学腐蚀电流为0.10A-0.60A时，停止电化学腐蚀；
    (5)后续处理及观察：当电流达到设置的电化学腐蚀终止电流值时，立即将试样从腐蚀剂中取出，用无水乙醇清洗干净后吹干保存，最后在扫描电子显微镜下观察第二相。
  2. 按照权利要求1所述的电化学腐蚀方法，其特征在于：步骤(1)中，试样的前期处理方法为：将待腐蚀的锆合金试样依次在150#、320#、800#、2000# 砂纸上打磨后，采用纳米SiO 2悬浊液进行机械抛光，直至试样呈光亮镜面。
  3. 按照权利要求1所述的电化学腐蚀方法，其特征在于，步骤(2)中，按体积百分比计，所述电化学腐蚀剂为以下五种配比之一：
    (a)8-12％的高氯酸和88-92％的甲醇；
    (b)8-12％的高氯酸和88-92％的乙醇；
    (c)8-12％的高氯酸和88-92％的乙二醇单丁醚；
    (d)8-12％的高氯酸和88-92％的正丙醇；
    (e)8-12％的高氯酸+88-92％的甲醇+乙醇+乙二醇单丁醚+正丙醇。
  4. 按照权利要求1所述的电化学腐蚀方法，其特征在于：步骤(2)中，按体积百分比计，所述电化学腐蚀剂由10％的高氯酸和90％的其它溶剂组成。
  5. 按照权利要求1所述的电化学腐蚀方法，其特征在于：步骤(4)中，待腐蚀试样表面和不锈钢片之间的距离为10mm。
  6. 按照权利要求1所述的电化学腐蚀方法，其特征在于：步骤(4)中，电化学腐蚀开始温度为-120℃～-100℃，电化学腐蚀终止电流为0.1～0.3A。
  7. 按照权利要求1所述的电化学腐蚀方法，其特征在于：步骤(4)中磁力搅拌器位于电化学腐蚀剂的底部，调节磁力搅拌器，使得转子带动电化学腐蚀剂形成上下贯穿的涡流，带去试样表面的腐蚀产物。
  8. 按照权利要求1所述的电化学腐蚀方法，其特征在于：所述方法用于在扫描电子显微镜下观察锆合金中第二相大小、形貌及分布。
PCT/CN2019/000249 2019-01-11 2019-12-18 一种观察锆合金纳米第二相的电化学腐蚀方法 WO2020142862A1 (zh)

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