材料期刊网

采用电子通道衬度(ECC)和电子背散射衍射(EBSD)技术研究了珠光体钢丝冷拉拔过程中微观组织的变化、铁素体微区取向与织构演变. 结果表明, 珠光体变形组织中存在剪切带(S带),它们的出现与渗碳体片条和拉拔方向之间的夹角有关: 夹角越大, S带越多.随着拉拔应变量的增大, 纵截面上珠光体片条逐渐转向拉拔方向, S带方向与拉拔方向的夹角逐渐减小. 珠光体内的S带会引起铁素体晶粒局部微区取向急剧变化, 从而使原有的珠光体团分裂成若干个由铁素体大角度晶界相隔的区域. 钢丝拉拔过程中形成平行于拉拔方向的铁素体<110>丝织构, 随着应变量的增大, 平行于拉拔方向的铁素体<110>丝织构增强, 其它丝织构组分减弱; 靠近钢丝中心区域内的<110>丝织构增强幅度大于其它区域.

Cold drawn high–carbon pearlitic steel wires have the highest strength of all mass–produced steel materials and are widely used in industry for a variety of applications, including cables for suspension bridges, steel cords for automobile tires and springs. At present the maximum tensile strength of high–carbon steel wires has already reached a value of 5.7 GPa. The properties of steel wires, including strength, fatigue properties and torsinal properties, are deeply affected by microstructure and ferritic micro–orientation and texture in the deformed pearlite. In this study, the evolutions of microstructure and ferritic micro–orientation and texture were investigated in a pearlitic steel wire during cld drawing using electron channel contrast (ECC) and electron backscatter diffraction (EBSD) techniques. The results show that there exist shear–bands (S–bands) in the deformed pearlite microstructure. Their appearance is related to the angle between cementite plates and the drawing axis: the larger the angle is, the more S–bands appear in the structure. The pearlite structure turns to the drawing direction and the angle between S–band and drawing axis decreases with the increase of strain.  The S–bands in the deformed pearlite colony induce the rapid change of local orientation of ferrite, and make the pearlite colony subdivide into several areas by high angle boundaries of ferrite. The strog h110i fibre texture f ferrite parallel to the drawing direction forms with the increase of strain, but the intensity of h110i fibre texture of ferrite is inhomogeneous from the cetre to surface in longitudinal section with the strongest in the centre and the weakest near the urface.