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在钢的应力腐蚀开裂敏感性测定中,新近的趋向是应用使用预裂试样的断裂力学方法[1]。这种方法可以消除使用光滑试样所经常遇到的点蚀形成之始发期。这些蚀坑起应力集中源的作用,由此产生应力腐蚀开裂。界限应力强度,称为K_(ISCC),已经由许多钢和合金中观察到,在应力强度高于该值的情况下发生应力腐蚀开裂。已经证实,K_(ISCC)与环境无关,而与预存裂纹的尖端形成拉延区相对应。拉延区一旦形成,就有助于其后的开裂过程,这是因为它作为裸露金属对原子氢释放起促进作用。而氢的释放又使裂纹尖端金属脆化,更进一步导至裂纹扩展和金属裸露。
In the determination of the susceptibility to stress corrosion cracking of steel, a recent trend is to apply the fracture mechanics method using pre-cracked specimens [1]. This method eliminates the onset of pitting corrosion often encountered with smooth specimens. These pits act as sources of stress concentration, resulting in stress corrosion cracking. Boundary stress intensity, known as K_ (ISCC), has been observed in many steels and alloys and stress corrosion cracking occurs at stresses above this value. It has been confirmed that K_ (ISCC) has nothing to do with the environment, but corresponds to the formation of drawing zone at the tip of the pre-stored crack. The draw zone, once formed, contributes to the subsequent cracking process because it acts as a bare metal to promote the release of atomic hydrogen. The release of hydrogen, in turn, embrittles the crack tip metal, further leading to crack propagation and metal nudity.