Strain-shock-induced early stage high pH stress corrosion crack initiation and growth of pipeline steels

[Display omitted] •Strain-shock is associated with steels having discontinuous yielding under load-control.•Effect of strain-shock exists in all stages of stress corrosion cracking during pipeline operation.•Mechanism of growth from early stage crack initiation and growth to growth above KISCC was proposed.•Microcrack initiation and coalescence to the main crack tip assisted the early stage crack growth.•Strain-shock is related to steels having discontinuous yielding under load-control, which exists in all stages of SCC during pipeline operation.•The slow strain rate testing approach could underestimate a material’s susceptibility to the SCC.•It sheds new insights into the design of materials susceptible to SCC. This investigation demonstrated the occurrence of strain-shock associated with steels having discontinuous yielding and its effect on high pH stress corrosion cracking (SCC) under load-control (e.g., internally pressurized pipeline), instead of displacement-control, for the first time. Results showed that microcrack initiation in the plastic zone and microcrack coalescence to the main crack tip were the main growth mechanism in the early stage of crack growth, distinct from the generally believed stochastic initiation and coalescence mechanisms. Discontinuous yielding associated with strain-aging would create a strain-shock effect under load-control and substantially enhance the early stage crack initiation and growth.