含有初始裂纹的低碳贝氏体钢的冲击韧性

Impact Toughness of Low-Carbon Bainitic Steel with Initial Cracks

通过热处理改变低碳贝氏体钢中的奥氏体及其转变物(M/A)分布形态,调整了钢的微观应力集中位置,并用弹塑性力学理论揭示了初始裂纹状态下提高贝氏体钢冲击韧性的力学机理.研究了相同化学成分的薄膜状M/A贝氏体和粒状M/A贝氏体的冲击韧度,结果表明:不论初始裂纹直接切过M/A或是绕过M/A,粒状M/A贝氏体的应力最大值集中于初始裂纹尖端,降低了材料抵抗冲击载荷的能力;杆状、薄膜状M/A贝氏体初始裂纹尖端处的应力集中位置不利于裂纹继续扩展,具有较高的冲击韧度.

An improved impact toughness of a low-carbon bainitic steel was achieved by a heat treatment that can alter the distribution map of M/A of the steel, which is the retained austenite and its transformation products, and thereby the location of the stress concentration. The mechanical mechanism contribu- ting to this improvement was revealed by elastic and plastic theorem. No matter initial cracks pass directly through M/A constituents or not, it is found that the bainitic structure with granular M/A demonstrates a deteriorated resistance to impact the load due to the significant stress concentration around the top of the initial crack, while the less severe stress concentration in the bainitic structure with film-like M/A retards the propagation of initial cracks.