Abstract
In this study, the tensile deformation behavior of an electron beam melted Ti−6Al−4V alloy was examined by in situ X-ray diffraction (XRD) line-profile analysis. The as-built Ti−6Al−4V alloy specimen showed a fine acicular microstructure that was produced through the decomposition of the α′-martensite during the post-melt exposure to high temperatures. Using high-energy synchrotron radiation, XRD line-profile analysis was successfully applied for examining the evolution of dislocation structures not only in the α-matrix but also in the nanosized, low-fraction β-phase precipitates located at the interfaces between the α-laths. The results indicated that the dislocation density was initially higher in the β-phase and an increased dislocation density with increasing applied tensile strain was quantitatively captured in each constitutive phase. It can be thus concluded that the EBM Ti−6Al−4V alloy undergoes a cooperative plastic deformation between the constituent phases in the duplex microstructure. These results also suggested that XRD line-profile analysis combined with highenergy synchrotron XRD measurements can be utilized as a powerful tool for characterizing duplex microstructures in titanium alloys.
Highlights
There has been a strong interest in additive manufacturing (AM), known as three-dimensional (3D) printing, as a revolutionized production route for industrial parts with complicated and/or optimized shapes
In electron beam melting (EBM) system, a highenergy electron beam is selectively scanned over a metal powder bed to produce three-dimensional (3D) parts via stacking the series of thin melted layers, which represent two-dimensional (2D) slices produced from a 3D computer-added design (CAD) model, in a layer-by-layer manner
It was found that the dislocation density values for both α- and β-phases increased simultaneously during tensile deformation
Summary
There has been a strong interest in additive manufacturing (AM), known as three-dimensional (3D) printing, as a revolutionized production route for industrial parts with complicated and/or optimized shapes. Among several metal AM processes that have been proposed so far, electron beam melting (EBM), a powder-bed-fusion AM process, is promising for fabricating more complicated geometries and realizing acceptable mechanical properties. The highly localized heat input and limited volume of the melt pool realize rapid cooling [4,5,6,7,8,9], resulting in a β → α′ martensitic transformation in Ti−6Al−4V alloy during the EBM process [9,10].
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