基于过冷奥氏体动态相变的热轧TRIP钢组织控制 Ⅰ.原始奥氏体晶粒尺寸

MICROSTRUCTURE CONTROL OF HOT ROLLED TRIP STEEL BASED ON DYNAMIC TRANSFORMATION OF UNDERCOOLED AUSTENITE I.Prior Austenite Grain Size

通过热模拟压缩实验,研究了铁素体相变前的奥氏体晶粒尺寸对基于动态相变的热轧C-Mn-Al-Si系TRIP钢组织及力学性能的影响。结果表明,减小原始奥氏体晶粒尺寸,可促进动态相变时的铁素体相变动力学,有利于铁素体、贝氏体及残余奥氏体等相分布更为均匀,获得的贝氏体束及贝氏铁素体尺寸较小,残余奥氏体的体积分数及C含量均较高,细小的颗粒状残余奥氏体数量较多且弥散分布,因此可获得具有较高强度和优良塑性的热轧TRIP钢。

Low-alloy multiphase transformation-induced plasticity（TRIP） steels offer excellent mechanical properties combining high-strength levels with a well ductility.This results from the complex synergy between different phases,i.e.,ferrite,baintie and retained austenite in them.An in-depth understanding of the novel hot rolled TRIP processing based on dynamic transformation of undercooled austenite（DTUA） is required to study the microstructure evolution under different treatment conditions. The parameters determining the stability of the metastable austenite and mechanical property of TRIP steel were revived and investigated experimentally,with a special attention paid to the effect of prior austenite grain size and cooling rate after DTUA on its microstructure and mechanical property. The results show that the kinetics of ferrite during DTUA is accelerated when the prior austenite grain size is small.In addition,reducing the grain size of austenite,the distribution of ferrite,bainite and retained austenite becomes more uniform.Moreover,the size of bainite packets and bainitic ferrite becomes smaller,the volume fraction and carbon content of retained austenite higher,and the finer granular retained austenite vast and distributed uniformly,which result in the investigated steel having a higher strength and ductility.