Defect evolution during high temperature tension-tension fatigue of SLM AISi10Mg alloy by synchrotron tomography

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

卷:792

Article

Bao, Jianguang^1,2  Wu, Shengchuan^3,4  Withers, Philip J.⁴  Wu, Zhengkai³  Li, Fei^1,5  Fu, Yanan⁶  Sun, Wei¹ 

[1] Univ Nottingham, Dept Mech Mat & Mfg Engn, Nottingham NG7 2RD, England

[2] Aircraft Strength Res Inst, Xian 710065, Shaanxi, Peoples R China

[3] Southwest Jiaotong Univ, State Key Lab Tract Power, Chengdu 610031, Peoples R China

[4] Univ Manchester, Henry Royce Inst, Dept Mat, Manchester M13 9PL, Lancs, England

[5] Chengdu Aircraft Ind Grp CO LTD, Chengdu 610092, Sichuan, Peoples R China

[6] Chinese Acad Sci, Shanghai Adv Res Inst, Shanghai Synchrotron Radiat Facil, Shanghai 201204, Peoples R China

关键词: Defect evolution;    X-ray tomography;    High temperature;    AlSi10Mg alloys;    Additive manufacturing;   

DOI  :  10.1016/j.msea.2020.139809

来源: Elsevier

【 摘 要 】

Lack of fusion defects and porosity are inevitable characteristics of additive manufacturing and these are expected to play a key role in determining fatigue life and fatigue failure when excluding the influence of inhomogeneous microstructures. This work followed damage accumulation under tension-tension cyclic loading at 250 degrees C in situ by time-lapse synchrotron radiation X-ray micro-computed tomography (SR-mu CT) for AlSi10Mg test-pieces, produced by selective laser melting (SLM) over their complete fatigue lives (ranging from 180 to 38,000 cycles). These samples were found to accumulate widespread plastic strain each cycle in common with ultra-low cycle fatigue (UCLF) at low levels of triaxial constraint. The defects were found to elongate plastically at a rate approximately 10 times larger than their growth rate laterally. This elongation behaviour at room and elevated temperature fatigue is proportional to the accumulated longitudinal strain increment each cycle. Rotation under the influence of shear is also observed for those defects close to the surface of samples. Some defect coalescence was observed, but final failure was found to be associated with the nucleation of a high density of secondary microvoids (occurring at eutectic Si platelets) that form just prior to failure and link up by microvoid coalescence. These steps may take up approximate 90% of the fatigue life. The final stage of cyclic plasticity occurs when the longitudinal strain exceeds similar to 0.9. Our results are in line with previous models of strain accumulation and defect growth under ULCF conditions.

【 授权许可】

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