Effects Of Post-weld Heat Treatment On The Growth Of Inter-metallic Compound Layer At Aluminum/Steel Solid-state Joining Interface

In recent years,due to the rapid development of automobile industry,vehicles are universal existence in the people’s daily life and the proportion is gradually increasing,gradually become the necessities in the people’s daily life;but the environment is becoming increasingly worse with the use of vehicle in large does and affecting the normal life of the residents,in order to achieve the sustainable development of human society,energy saving and emission reduction received the extensive attention of research in home and abroad.The main method of reducing the weight of body is using the light material aluminum substitute the steel in the vehicle structure,therefore the joining between aluminum and steel is absolutely necessary.However there is a big difference between aluminum and steel in physics、chemistry etc,so the brittle and hard inter-metallic compound is easily produced at the interface of aluminum/steel,the research of aluminum/steel dissimilar materials joining shows: interfacial intermetallic compound is the major factor of restricting the joint’s mechanical properties;therefore in order to obtain the superior aluminum/steel dissimilar material joint,we must restrain the growth of the interfacial inter-metallic;meanwhile we must study the growth mechanism of interfacial inter-metallic compound in order to find the way to restrict the growth of inter-metallic compound.The pure aluminum/Q235 mild steel dissimilar material were welded by using explosive welding in this text,studied the growth behavior of interfacial inter-metallic compound at the condition of different heat treat temperature 、 heat treat time,interfacial inter-metallic compound has different composition at the different heat treat condition,it’s thickness increased with the increase of heat treat temperature and heat treat time,it has a parabolic relationship between the thickness of inter-metallic compound and heat treat time.The maximum of interfacial inter-metallic compound120 μm was obtained at the condition when heat treat temperature was 600℃、heat treat time was 16 h.The mechanical properties and fracture appearance of the aluminum/steel joint were also analysis in this text,the mechanical property of joint receded with the increase of inter-metallic compound thickness,the higher of heat treat temperature、the longer of heat treat time the crack in inter-metallic compound was more,hence the mechanical property was more worse;the result of fracture analysis shows that: theposition of joint invalidation was mainly appear at the interfacial inter-metallic compound layer when the heat treat temperature was higher,the position of joint invalidation was mainly appeared at the inter-metallic compound layer and in the aluminum substrate.The growth activation energy Q and growth constant K0 of interfacial intermetallic compound was obtained according to Arrhenius equation,reached the kinetics relationship between inter-metallic compound thickness and heat treat temperature、heat treat time.