首页|Origin of surface oxidation induced the nucleation and propagation of microcracks in TNM alloy
Origin of surface oxidation induced the nucleation and propagation of microcracks in TNM alloy
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This study investigated the impact of surface degradation caused by oxygen(O)and nitrogen(N)ele-ments in the environmental atmosphere on the service failure of nearly lamellar TNM alloy.The results show that oxidation-induced phase transformations at the surface and subsurface regions strongly af-fect the alloy's tensile properties at high temperatures.The precipitation of Al2O3,which disrupts the integrity of the Ti2AlN layer,has a weaker deformation resistance capacity compared to the Z-phase.Un-der stress conditions,numerous dislocations concentrate at the Al2O3 phase,causing Al2O3 particles to easily detach and initiating crack nucleation at the Z-phase/Al2O3 interface.This is the origin of oxidation failure.Cracks nucleate at the Al2O3 detachment region,propagate,and connect with surface microcracks induced by the rough and loose outer oxide layer structure.This leads to the rapid propagation of cracks into the subsurface.The consumption of β-stabilizing elements at the surface,along with the internal dif-fusion of O and N elements into the subsurface region,results in the formation of the hard brittle Z-phase at the subsurface lamellar structure and a transition from β0 to α2 at the lamellar colony boundaries.The precipitation of α2 and Z-phase also accelerates crack propagation.In summary,the failure mode shifts from toughness fracture to brittle fracture.
Tnm alloyOxidationAl2O3Transmission electron microscopy
Yuqing Li、Hongchao Kou、Yarong Wang、Yonghao Yu、Zilong Zhang、Jinshan Li
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State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China
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