Study On Texture Inheritance And Its Mechanism Of High Strain Steel Wire

Pearlitic steel wires and ferritic steel wires were austenitizing treated in order to investigate texture inheritance and crystallographic orientation change during the transformation.Assisted by scanning electron microscope(SEM)and electron backscatter diffraction(EBSD)analysis,microstructure and texture before and after heat treatment were measured.By studying the misorientation angle distribution and using the method of reconstructed grain,the change of crystallographic orientation during ????? transformation was investigated.The relationship between pearlite alignment and crystallographic texture of ferrite in heat-treated pearlitic wires were discussed.Transmission electron microscope(TEM)was used to observe the microstructure of wires deformed slightly after heat treatment,in order to explore the influence of orientation on dislocation generation.The mechanism of texture inheritance in diffusion phase transformation was investigated by analyzing the inherited texture of large deformation ferritic steel wires.The results show that,the intensity of <110> texture increased with the increase of original strain.The growth of preferred austenite grains,which occurred with increase of austenitizing temperature and holding time,results in enhancement of <110> texture.During ????? transformation,variant selection occurred preferably in the form of twins or variants in the same close-packed plane.The inherited texture had certain stability in the process of ????? transformation repeatedly.Hence,the product phase might be inclined to nucleate and grow in similar orientation relationship.The large deformation pearlite steel wires was heat treated in order to explore the inherited texture involved carbon diffusion,and the relationship between the pearlite lamellae and the crystallographic orientation.The results show that after the austenization and salt bath cooling,elongated pearlite grains were reverted to equiaxed shape,distribution of lamellae direction was uniform and not preferred.The <110> texture was partially conserved after ????? transformation.With the increase of cold drawing strain,the intensity of <110> texture was enhanced.As the austenitizing holding temperature and holding time increased,the intensity of <110> texture decreased.The pearlite alignment did not have restricted match relationship with the orientation of ferrite phase in the heat treated wires.There were areas that had same pearlite lamellae direction but ferrite orientation changed,as well as areas that had same ferrite orientation but pearlite lamellae direction changed.The influence of the crystallographic orientation on the deformation of grain was discussed,and the dislocations in the initial stage of pearlite steel wire deformation was observed.The results show that,though the lamellae direction might be same,the Schmid factors were different because of the difference of ferrite orientation.Thus,microstructure and crystallographic orientation should be comprehensive considered when it came to deformation.The heat treated steel wires were drawn.When the drawing strain was tiny,dislocation occurs at the interface of ferrite and cementite.When the direction of the pearlite lamellae were approximately parallel to the drawing direction,the dislocations slipped on a single active slip system.When the direction of the pearlite lamellae were in a large angle with the drawing direction,the dislocations were activated on multi-slip systems.Dislocation lines were at various orientations because of the combined restriction of pining effect of cementite and tension.While drawing strain increases slightly,dislocations began to slip and tangle.The dislocation lines distributed at positions perpendicular to <110> direction of ferrite orientation.When pearlite lamellae were parallel to <110> direction of ferrite,dislocations were easier to slide across the film.While there were a large angle between pearlite lamellae and <110> direction of ferrite,dislocation piled up and resulted in cementite lamellae distorted and broken.