形变温度对中碳钢组织转变的影响

INFLUENCE OF DEFORMATION TEMPERATURE ON THE MICROSTRUCTURE TRANSFORMATION IN MEDIUM CARBON STEEL

热模拟单向压缩下中碳钢形变温度低于Ad3(786℃)点时,析出形变诱导铁素体(DIF),DIF量随形变温度降低而提高;在低于750℃形变时,DIF量远高于平衡态铁素体含量54%.DIF析出时碳原子高度富集在铁素体晶界和铁素体/奥氏体界面.在低于A1(719℃)等温处理时,高于Ad3点形变试样中,奥氏体转变为铁素体+片层状珠光体;低于Ad3点但高于Ar3(645℃)点形变时,未转变奥氏体转变为铁素体+片层状珠光体+晶界渗碳体;稍高于Ar3点形变时,将获得铁素体+弥散渗碳体的球化组织.

During uniaxial hot compression for a medium carbon steel, the deformation induced ferrite (DIF) appeared when deformed temperatures lower than A(d3) (786 V). The volume fraction of DIF increases with decreasing deformation temperature, especially when deformed temperatures lower than 750 degrees C the volume fraction of DIF increases significantly, which is far beyond the equilibrium ferrite fraction of 54%. With the increase of DIF, more and more carbon atoms were rejected into the boundaries of ferrite and interfaces of ferrite/untransformed austenite. During isothermal holding below A(1) (719 degrees C) temperature just after deformation, supercooled austenite would decompose to different structures in three different ways: when the deformation temperature is higher than A(d3), conventional ferrite-lamellar pearlite structure was obtained; when the deformation temperature is lower than A(d3) whereas higher than Ar-3 (645 degrees C), retained austenite transformed to ferrite-lamellar or degenerated pearlite-grain boundary cementite; when the deformation temperature decreased to just above A(d3), a microstructure different from lamellar pearlite was obtained, which consisted of fine cementite particle and ferrite.