The effect of loading direction on strain localisation in wire arc additively manufactured Ti-6Al-4V

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

卷:788

Article

Lunt, David¹  Ho, Alistair¹  Davis, Alec¹  Harte, Allan^1,3  Martina, Filomeno²  da Fonseca, Joao Quinta¹  Prangnell, Philip¹ 

[1] Univ Manchester, Oxford Rd, Manchester M13 9PL, Lancs, England

[2] Cranfield Univ, Welding Engn & Laser Proc Ctr, Cranfield MK43 0AL, Beds, England

[3] United Kingdom Atom Energy Author, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England

关键词: Titanium alloys;    Additive manufacturing;    Tensile;    EBSD;    Digital image correlation;    Strain localisation;   

DOI  :  10.1016/j.msea.2020.139608

来源: Elsevier

【 摘 要 】

Ti-6Al-4V microstructures produced by high deposition rate Wire Arc Additive Manufacturing (WAAM) can be both heterogeneous and anisotropic. Key features of the as-built microstructures include; large columnar beta grains, an a transformation texture inherited from the beta solidification texture, grain boundary (GB) a colonies, and Heat Affected Zone (HAZ) banding. The effect of this heterogeneity on the local strain distribution has been investigated using Digital Image Correlation (DIC) in samples loaded in tension; parallel (WD), perpendicular (ND) and at 45 degrees (45ND) to the deposited layers. Full-field surface strain maps were correlated to the underlying local texture. It is shown that loading perpendicular to the columnar beta grains leads to a diffuse heterogeneous deformation distribution, due to the presence of regions containing hard, and soft, a microtextures within different parent beta grains. The 'soft' regions correlated to multi-variant a colonies that did not contain a hard a variant unfavourably orientated for basal or prismatic slip. Far more severe strain localisation was seen in 45. ND loading at 'soft' beta grain boundaries, where single variant a GB colonies favourably orientated for slip had developed during transformation. In comparison, when loaded parallel to the columnar beta grains, the strain distribution was relatively homogeneous and the HAZ bands did not show any obvious influence on strain localisation at the deposit layer-scale. However, when using high-resolution DIC, as well as more intense shear bands being resolved at the beta grain boundaries during 45 degrees ND loading, microscale strain localisation was observed in HAZ bands below the yield point within the thin white-etching a colony layer.

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