Origin of surface oxidation induced the nucleation and propagation of microcracks in TNM alloy  

作　　者：Yuqing Li Hongchao Kou Yarong Wang Yonghao Yu Zilong Zhang Jinshan Li 

机构地区：[1]State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072,China

出　　处：《Journal of Materials Science & Technology》2024年第35期16-26,共11页材料科学技术(英文版)

基　　金：supported by the National Science and Technology Major Project(No.J2019-VI-0011-0125);Shaanxi Provincial Innovation Capacity Support Plan(No.2023-CX-TD-47);the ND Basic Research Funds of NPU(No.G2022WD).

摘　　要：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 Al_(2)O_(3),which disrupts the integrity of the Ti_(2)AlN layer,has a weaker deformation resistance capacity compared to the Z-phase.Un-der stress conditions,numerous dislocations concentrate at the Al_(2)O_(3)phase,causing Al_(2)O_(3)particles to easily detach and initiating crack nucleation at the Z-phase/Al_(2)O_(3)interface.This is the origin of oxidation failure.Cracks nucleate at the Al_(2)O_(3)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 ofβ-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 fromβ0 toα2 at the lamellar colony boundaries.The precipitation ofα2 and Z-phase also accelerates crack propagation.In summary,the failure mode shifts from toughness fracture to brittle fracture.

关 键 词：Tnm alloy OXIDATION Al_(2)O_(3) Transmission electron microscopy 

分 类 号：TG1[金属学及工艺—金属学]