Abstract
The fatigue behavior and fracture mechanisms of additively manufactured Ti-6Al-4V specimens are investigated in this study. Three sets of testing samples were fabricated for the assessment of fatigue life. The first batch of samples was built by using Laser-Engineered Net Shaping (LENS) technology, a Direct Energy Deposition (DED) method. Internal voids and defects were induced in a second batch of samples by changing LENS machine processing parameters. Fatigue performance of these samples is compared to the wrought Ti-6Al-4V samples. The effects of machine-induced porosity are assessed on mechanical properties and results are presented in the form of SN curves for the three sets of samples. Fracture mechanisms are examined by using Scanning Electron Microscopy (SEM) to characterize the morphological characteristics of the failure surface. Different fracture surface morphologies are observed for porous and non-porous specimens due to the combination of head write speed and laser power. Formation of defects such as pores, unmelted regions, and gas entrapments affect the failure mechanisms in porous specimens. Non-porous specimens exhibit fatigue properties comparable with that of the wrought specimens, but porous specimens are found to show a tremendous reduced fatigue strength.
Highlights
Additive manufacturing (AM) is a rapidly emerging technology for the fabrication of three-dimensional objects
The fatigue behavior of Ti-6Al-4V samples produced by Laser-Engineered Net Shaping (LENS) was analyzed
The static static strength of porous samples non-porous samples were almostidentical, identical,considerably considerably lower strength of porous samples andand non-porous samples were almost fatigue strength was observed for porous samples
Summary
Additive manufacturing (AM) is a rapidly emerging technology for the fabrication of three-dimensional objects. Unlike traditional manufacturing processes based on material subtraction (e.g., milling, turning, cutting) and forming methods (e.g., foundry, molding, stamping), AM processes are capable of building 3D geometries directly from digital models. Laser-Engineered Net Shaping (LENS) is a directed energy deposition method (DED). DED is commonly used for repair operations or to add additional material to existing components [1,2,3,4,5]. A nozzle is mounted on a multi-axis arm, which deposits melted material onto a specified surface, where it solidifies. The nozzle can move in multiple directions, and material can be deposited from any angle spanned by a 4- or 5-axis machine
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