Study Of Interfacial Structure And Bonding Strength For Roll-bonding Of Aluminum Film To Iron Plate

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.