Effect Of High Plasticity Sleeve On The Microstructure And Mechanical Behavior Of Mg-based Bimetal Plates

Mg-based bimetallic composites have attracted extensive attention in lightweight field for their excellent comprehensive properties.In this paper,Mg-based composite plate with high plastic sleeve was successfully prepared by co-extrusion.The effects of volume fraction and interface characteristics of high plastic sleeve on microstructure,texture and mechanical properties of Mg-based composite plate in extruded and annealed states were systematically studied.In addition,the effect of the volume fraction and interface characteristics of the high plastic sleeve on the microstructure and mechanical behavior of the rolled composite plate was also studied.The results of this paper show that:(1)The interface of the extrusion and annealed Mg-based composite plate is well combined,and there is no obvious crack.An obvious intermetallic compound is formed at the interface of the extruded AZ31/1100 composite plate.The diffusion layer thickness is about3 μm,and the diffusion layer thickness increases significantly with the increase of annealing time.There is no obvious intermetallic compound formation at the interface of AZ31/ZG21 composite plate before and after annealing.Different interface characteristics will significantly affect the interface structure of the rolled composite plate.When the thickness of the interfacial diffusion layer is about 3 μm,the diffusion layer is broken obviously in some areas of the composite plate after rolling.When the diffusion layer thickness is about 110 μm,the diffusion layer at the interface of the rolled composite plate is broken seriously.(2)The high plasticity ZG21 Mg sleeve and 1100 Al sleeve have little effect on the microstructure and texture of AZ31 core in extruded and annealed state.The average grain size of AZ31 core in extruded composite plate is 3 μm.After annealing,the average grain size of AZ31 core is obviously increased,and the texture types are mainly typical basal texture(<0002>∥ND).After rolling,the grain size of Mg and Al components of the composite plate is obviously refined,and the texture type of Mg components is still typical basal texture.(3)The interface characteristics of the extruded Mg-based composite plate have little effect on the plasticity of the plate,but the volume fraction of the high plastic sleeve has a significant effect on the plasticity of the extruded Mg-based composite plate.With the increase of the volume fraction of high plastic sleeve,the plasticity of Mg-based composite plate increases significantly.After annealing,the interface characteristics and the volume fraction of high plastic sleeve affect the plasticity of Mg-based composite plate.With the increase of diffusion layer thickness,the elongation of composite plate decreases greatly.Regardless of interface characteristics,the plasticity of annealed composite plate increases with the increase of volume fraction of high plastic sleeve.The volume fraction and interface characteristics of high plastic sleeve affect the plasticity of composite plate after rolling.The elongation of the composite plate increases with the increase of the volume fraction of the high plastic sleeve.Compared with the composite plate before rolling,the elongation of the composite plate after rolling is lower and decreases significantly with the increase of diffusion layer thickness.(4)The volume fraction of high plastic sleeve and interface characteristics have little influence on the applicability of the rule of mixtures(ROM)for the extruded Mg-based composite plates.The experimental elongations of the extruded AZ31/1100 and AZ31/ZG21 plates are close to the predicted ones,and the deviation between the predicted ones and the experimental ones is less than 3%.Different interface characteristics significantly affect the applicability of the ROM for the elongation of annealed Mg-based composite plates.When the thickness of the interfacial diffusion layer is about 95-155 μm,the elongation of the annealed AZ31/1100 plate is significantly different from the predicted elongation,and the deviation increases with the increase of annealing time,and the maximum deviation can reach16.1% after annealing for 10 h.When there is no obvious diffusion layer at the interface,the elongation of annealed AZ31/ZG21 sheet is very close to the predicted value of the ROM,and the deviation from the experimental value is less than 3%.