Study On Microstructure And Properties Of Hot Rolled Aluminum/Magnesium Composite Plate

The rehabilitation mechanism is the foundation for a rehabilitation robot to realize its motion,and the quality of the rehabilitation mechanism decides the rehabilitation effect of patients with the rehabilitation robot.The research of rehabilitation mechanism is……Al/Mg bimetallic laminated composites have attracted much attention because of their excellent properties.Magnesium alloys are lightweight structural metals with low density,and they have excellent properties such as high stiffness-to-weight ratio,high strength-to-weight ratio and good damping capacity.Thus,magnesium alloys have great potential in the automotive and aerospace fields.However,the application of magnesium and its alloys are still restricted due to their low corrosion resistance.In contrast,as structural materials,aluminum alloys are widely used in mechanical and aerospace fields due to their excellent properties,including light weight,high corrosion resistance,low cost,and good plastic formability.Therefore,the Al/Mg laminated composites which combine the advantages of substrates and achieve appropriate coordination have attracted worldwide attention.To study the variation of bonding strength of hot-rolled Al/Mg clad sheets,various rolling parameters such as reduction ratio,rolling temperature and rolling speed were comprehensively considered in this work,and 7075 Al/AZ31 B Mg composite plates were prepared by hot rolling with single pass.The results show that the dynamic recrystallization occurred in the microstructure of Mg matrix during the rolling process due to the heat and strong deformation,and the increasing rolling speed contributed to the complete dynamic recrystallization.At the same rolling temperature,the bonding strength of the Al/Mg composite plates increased first and then decreased with the increase of the reduction ratio;the bonding strength increased due to the increase of the elements diffusion width across the interface and the grain refinement near the magnesium interface.The bonding strength decreased because cracks occurred near interface of the magnesium matrix caused by the large deformation and the excessive heat was generated by the plastic work,resulting in the growth of the magnesium side grains caused by the increasing temperature of the magnesium matrix.The shearing test was carried out on the composite plates.When the shear strength of the Al/Mg composite plates was low,the shear fracture occurred at the interface with brittle fracture feature.While the fracture morphology presented ductile fracture with high shear strength,the fracture occurred on the Mg-alloy side.The thermocouple wire was inserted at the interface of the Al/Mg magnesium composite slab,and the interface temperature change during the rolling of the composite plate was measured.The influence of the interface temperature on the bonding properties of the composite plate and the microstructure of the magnesium matrix was studied.The final results show that when the interface temperature is above 410 ° C,the effect of the AZ31 B metallographic structure begins to exceed the strain.And the change in the bonding strength of the composite plate corresponds to the difference in magnesium grain size.