Quantitative characterization of machining-induced white layers in Ti-6Al-4V

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

卷:764

Article

Brown, M.^1,6  Crawforth, P.²  M'Saoubi, R.³  Larsson, T.³  Wynne, B.⁴  Mantle, A.⁵  Ghadbeigi, H.⁶ 

[1] Univ Sheffield, Ind Doctoral Ctr Machining Sci, Adv Mfg Res Ctr Boeing, Rotherham S60 5TZ, S Yorkshire, England

[2] Univ Sheffield, Adv Mfg Res Ctr Boeing, Rotherham S60 5TZ, S Yorkshire, England

[3] Seco Tools AB, Mat & Technol Dev, SE-73782 Fagersta, Sweden

[4] Univ Sheffield, Dept Mat Sci & Engn, Sir Robert Hadfield Bldg,Mappin St, Sheffield S1 3JD, S Yorkshire, England

[5] Rolls Royce PLC, Mfg Technol, Derby, England

[6] Univ Sheffield, Dept Mech Engn, Sir Frederick Mappin Bldg,Mappin St, Sheffield S1 3JD, S Yorkshire, England

关键词: White layer;    Surface integrity;    Titanium;    Machining;    Characterization;   

DOI  :  10.1016/j.msea.2019.138220

来源: Elsevier

【 摘 要 】

Machining-induced white layers can affect the functional performance of engineered components, due to the resulting mechanical and microstructural properties. Destructive inspection methods such as cross-sectional microscopy are typically used to identify white layers, however, these methods are inherently costly and time-consuming. It is, therefore, desirable to detect this anomalous surface feature using non-destructive methods which requires improved knowledge around the characteristics of white layers. The present paper reports on the characterization of white layers formed during machining of Ti-6Al-4V, to aid future development of a reliable non-destructive assessment method. The microstructure of the material in the white layer was found to have a basal (0002) alpha-hexagonal close packed texture and there was no evidence of an alpha ->beta phase transformation during white layer formation. The white layer has a highly refined grain structure with an increased nanohardness of up to 15% compared with the bulk material. It is proposed that white layers in Ti-6Al-4V are formed by continuous dynamic recrystallization driven by severe plastic deformation during machining. According to the measured micro-mechanical properties of the white layer, suitable non-destructive testing methods are suggested for the detection of this surface feature.

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