Microstructural influences on fatigue crack initiation and early propagation in Ni-based superalloy
MATERIALS SCIENCE AND TECHNOLOGY(2022)
摘要
Effects of unimodal secondary gamma' size and grain orientation on fatigue crack initiation and early crack propagation at room temperature have been investigated in RR1000 alloy. Fatigue tests show cracks mainly initiated at slip bands and/or pores followed by crystallographic facet formation while more diffuse strain localisation is observed around the pores by SEM-DIC analysis. Fatigue lifetime is linked to the number of crack initiations and consequent crack coalescence, which accelerates crack propagation. Slip trace analysis with EBSD mapping shows cracks are likely to propagate along the primary active slip system with a relatively high Schmid Factor. In the tests conducted here, the stochasticity of crack initiation events has more control on the overall lifetime than variations in secondary gamma' size.
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关键词
Ni-based superalloys, fatigue crack initiation, short fatigue crack growth, microstructural effect, strain localisation, Fatigue lifetime, Crack coalescence, Secondary gamma '
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