【作者】 王谦；

【导师】 杨春利； 闫久春；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2014， 博士

【摘要】 铝/铁复合板可以将铝与铁的直接焊接转化为铝合金与铝/铁复合板之间的焊接，避免铝与铁直接焊接时发生反应，生成脆硬金属间化合物，削弱连接界面强度，因此，该材料在工程领域具有广泛的应用前景。本文以轧制连接铝薄膜/铁板为目标，采用真空轧制连接方法，研究了铝薄膜/铁板轧制工艺参数对轧制连接界面结构及结合强度的影响规律，并分析了连接界面的形成机制；研究了铝/铁界面化合物形成规律及对界面结合强度的影响；提出了复合板结合强度定量测试方法及原理，并对测试试样的制备工艺进行了优化。本文建立了铝薄膜和铁板双金属轧制连接的受力模型，推导出轧制压力计算公式，计算了不同板宽和压下率时的铝薄膜轧制压力，分析了轧制的影响因素，确定了需要研究的铝薄膜和铁板轧制连接工艺参数有：轧制连接温度、压下率和轧制道次，并给出了这些工艺参数的研究范围。本文重点研究了铝薄膜/铁板的轧制连接工艺。研究发现，随轧制件预热温度升高，铝薄膜与铁板连接界面结合强度逐渐增加，最高可达94MPa；通过对比研究不同厚度铝薄膜与相同厚度铁板的轧制试验结果，发现在其它工艺参数相同的条件下，初始铝薄膜的厚度越大，复合板界面连接结合强度越低，产生连接的起始预热温度越高，因此，铝薄膜越厚，越不利于铝薄膜与铁板的界面结合；轧辊间隙越大，复合板总压下率越低，铝薄膜与铁板界面结合强度也越低；选用厚度为0.1mm铝薄膜和2mm铁板进行多道次轧制试验，研究发现，经第二次轧制后，连接界面结合强度有所提高，但是，经第三次轧制后，连接界面结合强度迅速下降，其原因主要是连接界面处产生了脆性的金属间化合物。在轧制试验的基础上，探讨了铝薄膜/铁板单道次轧制连接界面形成过程，以及多道次轧制界面金属间化合物的产生过程，并进一步对界面结合强度变化过程进行了讨论。当铝薄膜与铁板进行单道次轧制时，轧制力影响界面的形成，在此过程中，铝薄膜/铁板轧制连接界面结合强度的形成与轧制力密切相关，界面相互作用小，界面变形能低，界面的结合以相互嵌入的机械结合为主，界面结合强度较小；界面相互作用大，变形能高，界面的结合以金属原子键合为主，界面结合强度较大。当铝薄膜/铁板进行多道次轧制时，轧制产生并累积大量应变能，导致轧制连接界面在较低温度下也能应力诱导Fe-Al金属间化合物的生成，使界面结合强度下降。为了考察所制备的铝/铁复合板对工程应用的适应性，本文还研究了固态铝与固态铁界面反应物的结构，以及金属间化合物对铝/铁复合板界面结合的影响。实验结果表明，对于铝/铁复合板，在加热温度600°C以下、长时间保温的条件下(2小时)，连接界面不会产生金属间化合物；在加热温度610°C、保温时间15min的条件下，连接界面有金属间化合物Fe2Al5和FeAl3生成，这说明固态铝与固态铁反应开始发生,610°C是固态铝与固态铁产生金属间化合物的临界温度。提高加热温度或延长保温时间，金属间化合物层均会增厚，加热650°C、保温120min反应层厚度超过50μm。对存在不同厚度金属间化合物的铝薄膜/铁板的复合板进行剪切强度测试，结果表明，铝薄膜/铁板的界面结合强度较低，剪切强度仅为约20MPa，断裂均发生在金属间化合物层。对存在不同厚度金属间化合物的铝薄膜/铁板复合板进行轧制，研究发现，Fe-Al金属间化合物存在也会对铝薄膜/铁板的再次轧制产生负面影响。界面金属间化合物内部产生大量裂纹，甚至产生明显的界面分离。目前，已有关于薄膜与基体界面结合强度的评价方法以定性评价为主。为了有效评价铝薄膜/铁板轧制的质量，基于钎焊标准中剪切强度测试原理，本文提出了定量评价铝薄膜/铁板轧制连接界面结合强度的方法。在复合板铝薄膜侧连接合适尺寸的铝合金板，使之与铁板形成对称结构，构成剪切强度测试试样，然后采用万能拉伸试验机对试样进行剪切强度测试，所选材料和连接工艺应保证剪切强度测试时断裂或撕裂只发生在铝/铁复合板轧制连接界面处。基于上述测试原理，本文系统地研究了测试试样的制备工艺。通过对比研究确定了超声波辅助钎焊方法为试样制备的连接工艺，Zn-Al合金为钎料合金，5A06、7N01铝合金为匹配搭接板可选用的铝合金材料。在此基础上优化了超声波辅助钎焊工艺，其合适参数为：钎焊温度420C、超声波作用时间1s、焊缝预留间隙50μm。采用已有铝/铁复合板对测试原理及方法进行试验验证，证实了其有效性。更多还原

【Abstract】 The Al/Fe cladding materials can converting the problem of welding Alalloy with Fe into the problem of welding Al alloy with cladding materials toavoid the interaction between Al and Fe because of the intermetallics formeddecreasing the interfacial bonding strength, therefore, the Al/Fe claddingmaterials have broad application prospects in engineering field. The aim of thisdissertation was to fabricate Al/Fe cladding materials by roll-bonding. Themethod of vacuum roll-bonding was used. The influence rules of roll-bondingprocess parameters on the interfacial structure and bonding strength wereanalyzed. The mechanism of interfacail bonding formation was analyzed. Theformation rules and effect of intermentallics on the interfacial bonding werestudied. The principle and method of quantitative measurement for the bondingstrength of cladding materials was proposed. The fabrication process for the testwas optimized.The bi-metal force model for roll-bonding of aluminum film and iron platewas established. The calculation formula of rolling pressure was derived, andthen the rolling pressure of aluminum film with different plate width andreduction was calculated. The influence factors of roll-bonding were analyzed.The process parameters for roll-bonding aluminum film and iron plate neededresearch were determined. The objects were including rolling temperature,rolling reduction and rolling pass, and the scrope of the process parameters wasproposed.The process of roll-bonding aluminium film and iron plate was studied. Theresearch showed that, the bonding strength of the cladding materials wasgenerally enhanced with increasing preheating temperature, and the maximumstrength reached94MPa. Comparing the research using different initial thicknessof aluminium film with other parameters same, the bonding strength decreasedwhen the initial thickness of aluminium film increasing. And the preheatingtemperature, when the roll-bonding of aluminium film and iron plate produced,increased. Therefore, the increasing of initial thickness of aluminium film wentagainst the production the roll-bonding of cladding materials.With the roll gapincreasing, the reduction decreased, and the bonding strength of the claddingmaterials was also decreased. The muti-pass roll-bonding research was carriedout using0.1mm thick aluminium film and2mm thick iron plate as raw materials.After the second rolling pass, the bonding strength increased, while after thethird rolling pass, the bonding strength decreased, the reason was that the brittleness intermetallic compounds generated at the interface.Based on the roll-bonding experiment, the interfacial formation ofaluminum film and iron plate with single-pass roll-bonding and the formation ofintermetallic compounds with multi-pass roll-bonding were discussed, and theformation of interfacial roll-bonding was discussed. When the aluminum filmand iron plate was rolled with single-pass, the roll force impacted on theformation of interface. In the process, the interfacial bonding strength of cladmaterials was closely related to the roll force. When the interfacial interactionwas small, the interfacial deformation energy was small. The interface bondingmainly depended on mechanical bond which was resulted from materialsembedding in each other, and the interfacial bonding strength was lower. Whenthe interfacial interaction became large, the interfacial deformation energy waslarge. The interface bonding mainly depended on metallic bonding, and then thebonding strength increased. When aluminum film and iron plate was rolled withmulti-pass, lots of strain energy was produced and accumulated by rolling. TheFe-Al intermetallic compounds generated at lower temperature due to stressdriven, and then the bonding strength decreased.To investigate the applicability of aluminium/iron cladding materialsproduced by rolling, the structure of reactant between solid aluminum and ironand the effect of intermetallics on the interfacial bonding of cladding materialswas studied. The research showed that, when the temperature below600°C andthe holding time was120minutes, the intermetallic compounds did not generateat the interface of aluminium/iron cladding materials. When the temperature was610°C and the holding time was15minutes, the intermetallic compounds ofFe2Al5and FeAl3generated at the interface, and it showed that the solidaluminium and iron began to react. The temperature of600°C was criticaltemperature when the solid aluminium and iron began to react. Increasing thetemperature or holding time, the thickness of intermetallic compounds increased.When the temperature was650°C and the holding time was120minutes, thethickness of intermetallic compounds was more than50μm. The shear strengthtest carried out using cladding materials with different thickness of intermetalliccompounds. It showed that the bonding strength of cladding materials wasslower. The shear strength was only about20MPa. During the tensile strengthtesting, the fractures occurred in the intermetallic compound layers. The rollingexperiment carried out using cladding materials with different thickness ofintermetallic compounds. It showed that the intermetallic compounds hadnegative impact on cladding materials rolling again. Many cracks were observedin the intermetallic compounds and the aluminum film was clearly separatedfrom iron plate. At present, the evaluation methods for interface bonding strength of filmand substrate were mainly qualitative. To evaluate the quality of the claddingmaterials effectly, the method of quantitative measurement for the bondingstrength of cladding materials was proposed, which was based on the principleof shear strength test of the brazing and soldering standard. The aluminum filmof cladding materials was soldered with the suitable sizes of aluminum plate toform symmetrical structure with iron plate, and then the samples for shearstrength test were prepared. The shear strength test was carried out by theuniversal tensile testing machine. The sample and process should ensure that thefracture only occur at the interface of aluminum/iron cladding materials. Theultrasonic-associated soldering process, which used in the sample fabricationprocess, was studied. Through the study, the Zn-Al alloy was used as the fillermetal and the5A06and7N01alloys were used as the lapping plate for matching.The optimization process for ultrasonic-associated soldering was temperature of420°C, ultrasonic time of1s and soldering clearance of50μm. The test wascarried out with the cladding materials to verify the principle and method. Theresults verified the effectiveness of them.更多还原