| 6063 aluminum alloy/AZ31 magnesium alloy laminated bar and composite plate were prepared by casing extrusion and cladding laminated rolling method respectively.Optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and electron backscattering diffraction(EBSD)were used to analyze the grain morphology and element distribution characteristics of the interfacial layer and its two sides of the layered composite,and observe and analyze the bonding surface and tensile fracture morphology,element distribution characteristics and crystal orientation of the layered composite.Using the universal mechanical testing machine and micro hardness tester respectively evaluated the interface bonding strength of the layered composites and mechanical properties and microhardness distribution characteristics,analyzes in the 6063Al/AZ31Mg composite billet add zinc transition between layers of the influence of the layered composite bonding strength,and discusses the layered composite material interface mechanism;The corrosion resistance of the layered composite was analyzed by immersion corrosion test,and the corrosion morphology and corrosion surface were observed by SEM and EDS.The main research contents and results are as follows:1.The effects of heating temperature,heating method,extrusion speed and extrusion ratio on the uniformity of layer thickness of 6063 Al/AZ31 Mg laminated composite were studied.Under the experimental conditions,increasing extrusion ratio and decreasing heating temperature or adopting composite billet differential temperature heating and variable speed extrusion can improve the thickness uniformity of the composite.The composite billet is uniformly heated at 380?and the extrusion speed is reduced from 2.4mm/s to 0.8mm/s,and the composite billet is heated at 490?/360?and the extrusion speed is reduced from 1.6mm/s to 0.8mm/s.In the range of extrusion ratio from 14 to 43,the laminated bar with uniform thickness in transverse and longitudinal layers can be prepared.In the heating temperature range of 390-420?,the composite sheet with good microstructure and uniform thickness can be obtained by both symmetrical and asymmetric cladding rolling with zinc layer.2.The microstructure characteristics of 6063Al/AZ31Mg laminated composite rod and laminated composite plate were analyzed.Compared with the aluminum tube billet,the grain distribution along the extrusion direction of the aluminum alloy side of the interfacial bond layer in the composite bar is banded and have obvious orientation on the[001]inverse polar figure.Dynamic recrystallization occurs on the side grains of magnesium alloy in interfacial bond layer in composite bar,and fine equiaxed grains are formed,with average grain size in the range of 4-7?m.A good and defectless interface layer is formed in the composite bar.The grains on the aluminum alloy side of the interfacial bonding layer in the composite sheet are banded along the rolling direction.Compared with the magnesium slab,the grains in the interface layer of the composite sheet are dynamically recrystallized and refined.A good and defectless interfacial layer was formed in the laminated sheet rolled with zinc coating.3.The effects of heating temperature,extrusion speed and extrusion ratio on the interfacial behavior and bonding strength of Al/Mg laminated composites were studied,and the effects of adding zinc transition layer on the interfacial behavior and bonding strength of laminated composites were studied.With the increase of heating temperature,extrusion speed and extrusion ratio,the thickness of composite bar interface layer increases.Compared with uniform extrusion,the composite bar prepared by variable speed extrusion has higher bonding strength.The interfacial bonding strength of the composite bar is relatively uniform under the condition that the temperature is 380?and the extrusion speed is reduced from 1.6mm/s to0.8mm/s and the extrusion ratio is 23.The interfacial layer with thickness in the range of 2-9?m was formed by the introduction of zinc transition layer.The interfacial bonding strength of Al/Mg laminated composites can be improved by adding zinc transition layer.4.The interfacial bonding mechanism of Al/Mg laminated composites is discussed.In the process of high temperature plastic deformation,the oxide film on the billet surface is broken under the action of deformation force,and the matrix metal is exposed.Fresh metals are in contact with each other and interlock with each other under the action of force,but at this time,the energy on the material interface is low,and the materials do not diffuse or react with each other.Al/Mg laminated composites are mainly bonded by simple machinery at this stage,and the bonding strength is low.With the process of extrusion and rolling,the temperature rises gradually,the energy on the material interface rises gradually,and the metal atoms in contact with each other begin to diffuse and react.At this time,the bonding type of composite material changes to metallurgical bonding.5.The distribution law of microhardness of the section of 6063 Al/AZ31 Mg laminated composite material along both sides of the interface was verified,and the specific strength difference between the laminated composite bar and AZ31 magnesium alloy bar of the same size and 6063 aluminum alloy bar of the same size was compared and evaluated.The effect of adding zinc layer between the layers of the composite blank on the mechanical properties of the composite plate was studied.The immersion corrosion properties of the layered composite bar with AZ31 magnesium alloy and 6063 aluminum alloy were compared and analyzed.The microhardness of interfacial layer of layered composites is obviously higher than that of aluminum and magnesium alloy substrate on both sides of interface.The specific strength of composite bar is lower than that of single magnesium alloy bar,but higher than that of aluminum alloy bar,reaching 8.46×10~4Nm/kg.The addition of zinc transition layer increases the tensile strength of laminated sheet from 195.15MPa to 218.25MPa.After soaking in0.5%Na Cl solution for 24 hours,only slight pitting corrosion occurred on the surface of the composite bar and the 6063 aluminum alloy of the same size,and the corrosion degree of AZ31 magnesium alloy surface was serious,indicating that the aluminum layer of the composite bar had a good corrosion resistance. |
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