用钻孔压缩法在20钢、45钢、20CrMnTi钢内部引入裂纹,然后对含内部裂纹的试样进行不同加热温度和不同保温时间的热处理,采用光学显微镜及扫描电镜观察分析了裂纹愈合程度,研究了内部裂纹热处理愈合的形态变化规律.结果表明:结构钢内部裂纹愈合过程主要经历三个阶段；裂纹形变区的再结晶及其晶粒长大是结构钢内部裂纹愈合的主要机制,原子扩散是裂纹愈合的物质基础;裂纹愈合的内在驱动力为裂纹引起的系统能量的增高；裂纹愈合存在一临界愈合能量场因子,当内在与外界驱动能之和大于临界愈合能量场因子时,裂纹能愈合,反之裂纹不能愈合.

Internal cracks was introduced into 20,45 and 20CrMnTi steel by compressing drilled hole method,and then the cracked samples were heated at different temperatures for different times.Optical microscope and SEM are employed to examine the healing degree of the internal cracks.And the healing mechanism of the internal cracks by heat treatment were studied.The results indicate that there are three obvious stages during the cracks healing process and the main healing mechanisms of the internal cracks in structural steels are recrystallization and grain growth.The substance foundation of crack healing is atomic diffusion.The raise of strain energy or lattice distortion energy caused by the generation of the crack is the internal driving power of cracks healing.There should be a critical energy factor of crack healing.When the sum of the internal driving power and external driving power is higher than the critical energy factor,the cracks are healed.Otherwise,the crack can not be healed.