Study On Ductility-Enhancing And Strengthening Mechanism Of Y Micro-Alloyed 6.5% Si High-Silicon Steel And Evolution Of Microstructure And Texture In Hot And Warm Rolling

High silicon steel owns excellent soft magnetic properties such as low iron loss,high permeability and near-zero magnetostriction.However,high silicon steel cannot be produced in large scale by conventional rolling processes due to serious hard brittle led by the existence of ordered phases?B2 and DO₃?hindering its industrial production and practical application.Therefore,Fe–6.5wt%Si alloys without Y and with 0.03wt%Y are selected as objects.Elevated temperature tensile test,hot compression test,hot and warm rolling experiments are carried out for studying the effect of Y on the ductility of Fe–6.5wt%Si alloy.The constitutive equation and processing map of two kinds of high silicon steel were established for hot and warm rolling experiment based on the processing map to study the effect of Y on the microstructure and texture evolution of hot and warm rolling.Main results of this work are as follows:?1?Y refines the grain of forging slab,reduces the domain size of ordered phase and ordering degree for hardness reduction.What's more,elongation,reduction of area and tensile strength are improved by Y addition in Fe–6.5wt%Si alloy at 200⁸00?.The increasing ductility of Fe–6.5wt%Si alloy can be attributed to grain refinement and ordering degree reduction.?2?Y increases the average deformation activation energy of high silicon steel at600⁹00?and strain rate range of 0.01¹0 s^-1,Obviously,Y reduces the instability zone condition range,expands the optimal processing condition range and greatly inhibits the microcrack growth for improving deformability.On the one hand,the grain size of the forged blank containing Y becomes finer before hot compression,which plays a role in fine grain strengthening.On the other hand,small RE inclusions such as Y₂O₃ and YS can pin grain boundaries and dislocations,strengthen grain boundaries and hinder dislocation movement,resulting in an increase in dislocation density and destroyed the ordered structure,further refining B2-ordered domains,which is conducive to plastic softening.In addition,Y increases the proportion of coincidence-site-lattice boundaries?CSL?boundary,which is beneficial to the stress release at the microcrack tip,hinders the crack expansion,and also improves the ductility of Fe–6.5wt%Si alloy.?3?Small RE inclusions hinders the movement of dislocations and forms larger shear bands during the warm rolling process.In the subsequent annealing process,Y pins the grain boundaries,hinders the migration of grain boundaries,inhibits the grain growth and reduces the recrystallization ratio,Also,Y greatly weakens the intensity of{001}<100>texture in forging slab and main texture intensity during each process,but no obvious influence on the texture type.The grains with strong{001}<100>in forging slab rotate to{001}<110>during hot rolling,then almost no changes of the texture type but the intensity weakened in the normalizing process.It is shown that crystal rotation from unstable{001}<110>to stable{112}<110>or?texture along the?orientation line can be investigated in warm rolling.After annealing,the deformed?texture transforms to recrystallized?texture,and?*texture?{h11}<1/h,1,2>?is formed.Texture transition paths of the Fe–6.5wt%Si alloys during hot and warm rolling and annealing are as shown:{001}<100>?{001}<110>?{112}<110>+{111}<uvw>?{h11}<1/h,1,2>+{111}<uvw>.