C－Mn焊缝裂纹试样低温解理断裂机理

Cleavage Fracture Mechanisms of C-Mn Weld at Low Temperature in Precracked Specimens

在系列低温下，对Ｃ－Ｍｎ焊缝进行了裂纹张开位移（ＣＯＤ）试验，测量了力学性能和断口微观参数，对疲劳裂纹前端形核并长大的微孔和解理微裂改进行了观察。根据实验结果对Ｃ－Ｍｎ焊缝ＣＯＤ试样的低温解理断裂机理进行了分析，发现在低温区，Ｃ－Ｍｎ焊缝的解理断裂临界事件随温度升高发生由起裂控制，第二相、夹杂物尺寸微裂纹扩展控制和铁素体晶粒尺寸微裂纹扩展控制的转变，并对发生这种转变的微观机制进行了分析。

In this investigation,a series of crack opening displacement(COD)tests are car-ried out at several low temperatures for C-Mn weld steel.The mechanical properties and mi-croscopic parameters on facture surfaces were measured.The distributions of the elongatedcavities and the cleavage microcracks in front of fatigue crack tips are observed. Based on theexperimental results,the cleavage facture micromechanism of the COD specimen for C-Mnweld steel at low temperature are analysed,It is found that,with increasing temperature,thecritical event of the cleavage fracture changes fron the initiation controled to the propagationcontroled due to second phase or inclusion-sized microcrack as well as ferrite grain-sized mi-crocrack,and the micromechanism of this change is analysed.