Combining with the results of implant test, the conclusion that the main reason of dropping the strength of Austenite zone is the micro-crack located in the tip of flake graphite and Marten site is drawn.

• 结合插销试验结果提出了马氏体相变过程中，在片状石墨尖端及马氏体组织中造成的微裂纹是奥氏体区强度下降并进而在外力作用下断裂的主要原因。