奥氏体形变对仿晶界型铁素体/粒状贝氏体复相钢组织和强韧性能的影响

INFLUENCE OF AUSTENITE DEFORMATION ON THE MICROSTRUCTURE STRENGTH AND TOUGHNESS OF THE GRAIN BOUNDARY ALLOTRIOMORPHIC FERRITE/GRANULAR BAINITE (F_(GBA)/GB) DUPLEX STEEL

通过Gleeble-1500热力模拟实验机对仿晶界型铁索体/粒状贝氏体复相钢进行了Ar_3以上不同温度、不同形变量的平面应变压缩实验。SEM和TEM观察表明,奥氏体形变不仅细化仿晶界型铁素体,而且促进先共析铁素体在原奥氏体晶内形核,从而有利于细化粒状贝氏体晶团及其内部的铁索体片条和MA岛,给出的组织变化模型可阐述形变对粒状贝氏体精细结构的影响。经过780℃下30％形变,即使在形变后空冷的条件下也获得了平均长度小于5/μm、平均宽度小于2.5μm的仿晶界型铁素体晶粒、平均粒径小于3μm的晶内铁素体,与未经过形变的试样相比,CVN常温冲击韧性值从未形变的43J提高到108J,Vickers硬度从242提高到312,为工业生产工艺的改进提供了重要根据。

The plane strain compressive deformation experiments with various deformation amounts have been carried out on the grain boundary allotriomorphic ferrite/granular bainite (F-GBA/GB) duplex steel at temperatures above A(r3) using Gleeble-1500 machine. SEM and TEM observations indicate that the prior austenite deformation not only refines the allotriomorphic ferrite grain but also promotes the nucleation of intragranular ferrite, both of which in turn contribute to the refinement of granular bainite cluster including its ferrite platelets and MA islands. A model was proposed to elucidate the effect of prior deformation on the refinement of granular bainite cluster and its detailed microstructure. For specimens deformed by 30% at 780 degreesC and subsequent air cooling, F-GBA grains of an average size less than 5 mum and intragranular ferrite grains less than 3 mum were gained. Compared with specimens without prior deformation, the Charpy V-notch (CVN) impact energy and Vickers hardness is increase from 43 J to 108 J and from 242 to 312, respectively.