Competitive relationship during fatigue-crack initiation of friction-stir-welded Al alloy

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:809

Article

Liu, Zepeng¹  Zhang, Hongxia¹  Hou, Zhenguo²  Yan, Zhifeng¹  Liaw, Peter K.³  Dong, Peng¹ 

[1] Taiyuan Univ Technol, Coll Mat Sci & Engn, Taiyuan 030024, Peoples R China

[2] CRRC Tangshan Co Ltd, Dept Special Welding Proc, Tangshan 063035, Peoples R China

[3] Univ Tennessee, Dept Mat Sci & Engn, Knoxville, TN 37996 USA

关键词: Aluminum alloy;    Surface treatment;    Stress intensity factor range;    FGA;    Fatigue life prediction;   

DOI  :  10.1016/j.msea.2021.141006

来源: Elsevier

【 摘 要 】

In the present work, uniaxial fatigue tests (R = 0.1) showed that for high-strength aluminum alloys, the crack origin also presented a tendency of transition from the outside to the inside with the stress decreasing. The interior crack-initiation mode has a characteristic of a fish-eye embracing fine granular area (FGA) originated from an inclusion. Moreover, the formation mechanism of FGA was discussed. The values of the stress intensity factor (SIF) range of a surface mode and an internal mode were calculated. The results showed that Delta K-FGA keeps constant with an average value of 1.84 MPa.m(1)(/)(2), which was close to the interior crack-growth threshold (Delta K-th, (i)), 1.911 MPa.m(1)(/)(2). Paris-Hertzberg law was used to predict the life of fatigue-crack initiation and propagation during internal fracture. The crack-growth rate within FGA and fish-eye was also estimated. Furthermore, the competitive relationship between the interior and surface cracks initiation of welded joints was discussed through the SIF range.

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