板条马氏体钢的断裂韧性与缺口韧性、拉伸塑性的关系

THE RELATIONSHIP BETWEEN FRACTURE TOUGHNESS AND NOTCH TOUGHNESS, TENSILE DUCTILITIES IN LATH MARTENSITE STEEL

研究了超高强度板条马氏体钢的平面应变断裂韧性与缺口韧性、拉伸塑性之间的关系。实验结果表明，断裂韧性受控于裂尖前沿很小范围内（1—2倍临界裂纹张开位移c）显微组织的微观塑性，钝缺口韧性、拉伸塑性则受控于奥氏体晶粒尺寸或板条束直径。特征距离与裂纹尖端钝化所产生的有效变形区尺寸（2c）相对应。并提出断裂韧性与缺口韧性、拉伸塑性的关系取决于尖裂纹前沿有效变形区尺寸（2c）与原奥氏体晶粒尺寸（dγ）的相对大小。当2c＞（1－2dγ）时。

The relationship between fracture toughness and notch toughness, tensile ductilities in lath martensite steel has been investigated. The experimental results show that fracture toughness is controlled by microplastisity in the small local region (1 to 2 times the crack tip opening displacements c at critical) ahead of the crack tip, whereas blunt notch toughness, tensile ductility is controlled by austenite grain size (dγ) or martensite packet diamiter (dp). The characteristic distance corresponds to the extent of effective deformed region (2c) resulted from blunting of crack tip. The relationship between fracture toughness and notch toughness 、tensile ductility depends on the relative size of effective influence region (2c) and austenite grain. When 2c> (1 - 2dγ), the fracture toughness coincides with notch toughness, tensile ductility.