The Research Of The Formation Process Of The Intracrystalline Shear Bands In Fe/Fe And Fe/Ni Laminated Composite

Multi-layered composite materials have been payed much attention due to their excellent combination of physical,chemical and mechanical properties,which is attributed to the very high volume density of boundaries and interfaces within the matrix.The mechanic dissimilarity of each constitute inside the composite material leads to the stress incompatibility among boundaries and interfaces.This stress incompatibility also result in the formation of shear band at the boundary and interface,thus changing the performance of matrix material.As one of the most important microstructure during metal rolling deformation,the formation of shear band,including its size,density,angle and orientation,is significantly affected by the cold rolling reduction,and affects remarkably the formation of primary recrystallization texture.Up to date,much attention has been paid on the mechanistic investigation into the formation of macroscopic shear bands,but researchers also sees a paucity of literature focusing on the formation behavior of intracrystalline shear bands in multilayered compsite materials.In this thesis,Fe/Fe and Fe/Ni composite materials were successfully prepared by hot roll bonding.The evolution of shear bands in the multi-layer metal composite during cold rolling and recrystallization nucleation was studied.Effect of bcc/bcc and fcc/bcc on intracrystalline shear bands behavior in bcc metal was studied.The main findings are as follows:(1)As the reduction rate increasing,the fraction of intracrystalline shear bands area in Fe layers in the multi-layer composite board increases.The Goss orientation is the main nucleation orientation of shear band in Fe layers.The change of accuracy of Goss orientation in Fe/Fe composite is slight when rolling reduction increases from 60%to 80%.The accuracy of Goss orientation in Fe/Ni composite is higher under 80%rolling reduction than 60%reduction.(2)The Fe/Fe interface stimulates the initiation of intracrystalline shear bands.The number of shear bands increases continually as the reduction rate increasing to 80%.The additional shearing stress on the Fe/Ni interface promotes the earlier initiation of shear bands.The number of shear bands increases with strain,stabilizes after 60%reduction,and decreases after 80%reduction.(3)The effect of interfaces on the recrystallized Goss texture depends on the cold rolling reduction.The area fraction of Goss orientation in Fe/Ni composite is higher than Fe/Fe composite under 60%reduction rate.The area fraction of Goss orientation in Fe/Ni composite decreases and the area fraction of Goss orientation in Fe/Fe composite increases to a higher level than Fe/Ni composite under 60%reduction rate.