奥氏体变形及冷却速率对低碳贝氏体组织中大角晶界分布的影响

使用电子背散射衍射技术研究了低C高Mn高Nb成分设计下,非再结晶奥氏体变形及加速冷却速率对低碳贝氏体组织取向差特征和大角晶界分布的影响.结果表明,与原奥氏体晶粒内部的相变组织相比,原奥氏体晶界附近具有更高的大角晶界密度,非再结晶区奥氏体变形及快速冷却都有利于提高共格相变的驱动力、弱化变体选择以及有效增加大角晶界密度.此外,非再结晶区的大变形除了可充分压扁奥氏体晶粒和增加单位面积的奥氏体晶界密度外,还导致奥氏体晶界上细小的非共格转变铁素体晶粒生成,且这些铁素体晶粒与相邻组织表现出大取向差. 

Effect of ausforming and cooling rate on the distribution of high angle boundaries in low carbon bainitic structure

High Mn-high Nb micro-alloyed steels were investigated by electron back-scattering diffraction (EBSD) to determine the effect of cooling rate and ausforming on the characteristic of misorientation and the distribution of high angle boundaries (HABs) in low carbon bainitic microstructure. The results indicate that there is a dispersion of HABs interspacing from prior austenite grain boundaries to the grain interior. Both fast cooling and ausforming raise the drive force of coherent transformation, weaken variants selection, and are helpful for the increasing of HABs density near the boundaries and in the grains. Moreover, a larger deformation below the non-recrystallization temperature not only can flatten the austenite grains fully, but also can generate incoherent nucleation of fine ferrite grains at the prior austenite boundaries. Also the fine ferrite grains have significant misorientations with adjacent microstructure.