【摘要】 利用热模拟压缩变形实验研究了低碳含铌钢基于过冷奥氏体动态相变细晶双相钢的组织控制。相变前的奥氏体状态(再结晶奥氏体或形变奥氏体组织)及Nb的存在状态对动态相变有较大的影响。结果表明,由于铌在再结晶奥氏体中主要以固溶状态存在,其固溶拖曳作用延迟了铁素体动态相变,要求在动态相变中施以大的应变量才能获得细小马氏体岛弥散分布于细晶铁素体中的双相组织;形变奥氏体中,大部分铌在奥氏体未再结晶区形变中应变诱导析出,动态相变中固溶铌拖曳作用的降低以及未再结晶区形变对奥氏体有效晶界面积(Sv)的提高均有利于铁素体在动态相变中快速形核,在小应变量下即可获得铁素体晶粒为1~2μm,马氏体岛<1μm的超细晶双相组织。更多还原

【Abstract】 The effect of Nb on dynamic transformation and the microstructure control of ultra-fine grained dual phase steel based on the dynamic transformation of supercooled austenite were studied using hot compression simulation machine.The dynamic transformation was affected strongly by the status of Nb and austenite (recrystallized or deformed).The results show that Nb is mainly solutioned in recrystallized austenite,which restrained the dynamic transformation of ferrite through drag effect of Nb and is not benefit for obtaining fine grained dual phase microstructure with minor martensite islands distributing in ferrite matrix uniformly with low strain.In deformed austenite,significant strain-induced precipitation of Nb(C,N) occurres during the deformation in unrecrystallized zone of austenite.The weakening of drag effect of solute Nb and increasing of S_v value in the deformed austenite enhance the nucleation of ferrite during the dynamic transformation.In the Nb-microalloyed steel,fine grained dual phase steel with ferrite grain size of 1～2μm and martensite islands smaller than 1μm can be obtained by controlling dynamic transformation of deformed austenite with relatively low strain.更多还原