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| MECHANISM OF HYDROGEN INDUCED DELAYED PLASTICITY |
| Chu Wuyang; Xiao Jimei (Hsiao Chi-mei); Li Shiqiong; Ju Shuyan (Beijing University of Iron and Steel Technology; Beijing) |
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Cite this article:
Chu Wuyang; Xiao Jimei (Hsiao Chi-mei); Li Shiqiong; Ju Shuyan (Beijing University of Iron and Steel Technology; Beijing). MECHANISM OF HYDROGEN INDUCED DELAYED PLASTICITY. Acta Metall Sin, 1982, 18(1): 47-57.
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Abstract For various carbon and low-alloy steels with a wide range of the tensile strength, the effect of hydrogen on the apparent yield stress, which is a necessary exterior stress to produce the local macroscopi c plasti c deformation, was investigated with smooth tensile, bending, pre-cracked type Ⅰ-, type Ⅲ- and combined type Ⅰ+Ⅲ specimens. The results show that the effect of hydrogen on the yield strength of a smooth tensile specimen is insignificant, the difference between the charged and uncharged specimens is less than 10％. However, for the smooth bending or pre-cracked Ⅰ-type specimen with a. tensile stress gradient, hydrogen can decrease the apparent yield stress considerably if the strength of steel and the amount of hydrogen entering into the specimen exceed their critical values. This is the cause of hydrogen induced delayed plastic deformation and hydrogen induced delayed cracking.The effect of hydrogen on the apparent yield stress increases with increasing strength of the steel and average hydrogen concentration in the specimen. The reduction of the apparent yield stress of charged pre-cracked specimens is more evident than that of smooth bending ones. The hydrogen induced apparent yield stress reduction is a phenomenon controlled by hydrogen diffusion, it depends markedly on the strain rate and test temperature.For type Ⅲ- cracked specimens, in which there is no hydrostatic stress the apparent torsional yield stress of the charged specimens does not decrease and K_(ⅢH)=K_(ⅢC). But hydrogen induced delayed plasticity and cracking can occur on the specific plane inclined at an angle of —45° to the original crack plane, For combined type Ⅰ+Ⅲ specimens, the apparent torsional yield stress can be decreased only when K_1 is so large that hydrogen induced delayed plasticity can occur under the action of K_1 itself.
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Received: 18 January 1982
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