调质态07MnNiMoDR钢脆性断裂机制及冲击功离散性

测试了调质态07MnNiMoDR钢的冲击功,研究了其在DBTT区间的脆性断裂机制.结果表明,调质态07MnNiMoDR钢在DBTT区间的解理断裂由贝氏体束尺寸控制;存在一个临界尺寸,当形成于贝氏体束内的微裂纹尺寸达到这个临界值,并在正应力作用下穿过贝氏体束界扩展至相邻贝氏体束时,发生脆性解理断裂.另外,在DBTT区间的冲击断裂过程中,粗大贝氏体束的离散分布将使得脆性断裂载荷值不稳定,并最终导致冲击功出现离散.因此,通过控制调质态07MnNiMoDR钢中贝氏体束尺寸并使其均匀分布,能够有效提高其在DBTT区间的冲击功及降低冲击功离散性.

Brittle Fracture Mechanism and Impact Energy Scattering of Quenched and Tempered 07MnNiMoDR Steel

The impact energy of quenched and tempered (Q&T) 07MnNiMoDR steel was measured. The brittle fracture micro-mechanism in the ductile-brittle transition temperature (DBTT) region was studied. The results showed that the brittle fracture behavior is controlled by bainitic packets size. A critical packet size exists. When a micro-crack formed in the bainitic packet with a size exceeding the critical size propagates into adjacent packets under normal stress， brittle cleavage fracture occurs. The discrete distribution of the coarse bainitic packets leads to the scatter of brittle fracture load， which results in the impact energy scattering. It is suggested that homogenizing the distribution of fine bainitic packet sizes is an effective method of improving the impact energy and reducing its scattering in the DBTT region.