Magnesium Alloy And Aluminum Alloy Hot-rolled Composite Basic Research

Magnesium and aluminum has a low density and relative high-strength with extensive application,and the two materials has many similar characteristics.So the connection between aluminum and magnesium has good prospects to the application.For example, magnesium/aluminium composite board used in cars can lose weight and reduce shock; besides,aluminum is better anti-corrosion,which wrapped outside magnesium alloy can improve the overall corrosion resistance.But the traditional melting welding can produce the brittle phase,crack,air hole,deformation and other defects;heat-affected zones are too broad; and also with many other disadvantages.The study of other connection methods between magnesium and aluminum is still in its preliminary stage which needs more in-depth research.We try to bond ZK60 magnesium alloy and 7075 aluminum alloy by hot rolling in the air, which belongs to the solid-phase connection.The focus of this paper is the basic research of the hot-rolling between the two materials,including:the mensuration of the coefficient of thermal expansion,calculation of thermal stress,deformation resistance and simulant hot-rolling,and we analyse structure and performance by OM,SEM,EDS,shearing strength test,and so on,so as to further the work better.Through experiments,we find that:magnesium alloy has bigger coefficient of thermal expansion than 7075 aluminum alloy,the thermal expansion coefficient of casting magnesium-alloy turns smaller after deformation.Without considering the plastic deformation, the relationship between one-dimensional stress in aluminum alloy,the thermal expansion coefficient and△T is as follows:σ= C₀(α_Mg-α_A1)△T.The compression deformation resistance of ZK60 and 7075 increases with reducing of temperature and increasing of strain rate,and respectively the average activation energy of ZK60 and 7075 are 133.5 kJ/mol and 171.5 kJ/mol.By the linear regression,respectively,the heat deformation dynamic equations of 7075 the ZK60 are(?)_Mg=0.0068σ^6.67exp(-16054/T)and(?)_Al=e^28.03[sinh(0.01139σ)]^6.88 exp(-171476/RT);In the process of thermal compression deformation of ZK60,there comes obvious dynamic recrystallization which gets more full as deformation turns bigger,the strain rate gets lower,and the temperature of deformation becomes higher.The appropriate temperature gradient can reduce the heat stress in the interface,raising the deformation coordination capacity of the two materials in the rolling process;After chemical plating zinc, a layer of thin,brittle and more dense protective film comes out on the surface of ZK60, which significantly improves the combination strength of the interface.In a certain extent,as the total reduction rate increases and the temperature of rolling becomes lower,the gaps of the oxide film at the interface increase,and more fresh metal uncovers,so the interface bonding strength gets higher.The best parameter of the rolling process is:chemical plating zinc on the surface of ZK60,respectively,the rolling heating temperature of ZK60 and 7075 are 300℃and 380℃, the total deformation rate is 68.6 percent,and the corresponding interface shearing strength reaches 28.3 MPa.By protective atmosphere,and heat treatment after actual rolling,the combination of the interface should be better improved to meet practical needs.