Directed Energy Deposition versus Wrought Ti‐6Al‐4V: A Comparison of Microstructure, Fatigue Behavior, and Notch Sensitivity

Abstract

Laser Engineered Net Shaping (LENS), a Direct Energy Deposition (DED) additive manufacturing process is a 3D manufacturing process generally used to produce fully dense parts or to repair/add additional material to an existing component. The main aim of this work is to evaluate the fatigue behavior of LENS specimens in the presence of geometrical discontinuities and to compare its performance to the one obtained from wrought specimens. For this aim, axial fatigue tests are carried out on three sets of specimens namely, smooth, semi‐circular and V‐notched specimens to determine the fatigue strength and notch sensitivity of the LENS and wrought Ti‐6Al‐4V materials. The LENS material shows higher fatigue strength and notch sensitivity compared to wrought material which is attributed to the unique microstructural features leading to different fatigue failure mechanisms. Further, the fatigue data is assessed by use of strain energy density as a failure criterion.

Comparative Quality Control of Titanium Alloy Ti–6Al–4V, 17–4 PH Stainless Steel, and Aluminum Alloy 4047 Either Manufactured or Repaired by Laser Engineered Net Shaping (LENS)

“…Ti-6Al-4V is the most commonly processed titanium alloy, both by DED and by PBF. Its processing by LENS has also been reported [ 9 , 23 , 24 , 25 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ].…”

“…Prabhu et al [ 81 ] found that in spite of the expectation that partially melted particles at the surface would trigger crack initiation and decrease the fatigue life significantly, LENS-processed Ti-6Al-4V had fatigue life comparable to the wrought alloy, and may be used both for printing from scratch and repair without the need for HIP. Finally, Razavi and Berto [ 82 ] found that LENS-processed Ti-6Al-4V had higher fatigue life and fatigue strength compared to its counterpart wrought alloy. This was attributed to the finer grain size in the LENS alloy, which leads to higher fatigue crack nucleation time, and to the basket-weave and columnar prior β grains in its microstructure, which leads to higher degree of tortuosity and, accordingly, more roughness-induced closure effects during crack propagation [ 82 ].…”

“…Finally, Razavi and Berto [ 82 ] found that LENS-processed Ti-6Al-4V had higher fatigue life and fatigue strength compared to its counterpart wrought alloy. This was attributed to the finer grain size in the LENS alloy, which leads to higher fatigue crack nucleation time, and to the basket-weave and columnar prior β grains in its microstructure, which leads to higher degree of tortuosity and, accordingly, more roughness-induced closure effects during crack propagation [ 82 ].…”

The Low-Cycle Fatigue Behavior, Failure Mechanism and Prediction of SLM Ti-6Al-4V Alloy with Different Heat Treatment Methods

“…The function f (ϕ) presents the microporosity level ϕ. More detailed descriptions and explanations of the MSF model were reported in [45][46][47][48][49][50][51]. Among the MSF model parameters, the constants and coefficients in Equations ( 9)-( 13) for MSF prediction were calculated with reference to the experiment results herein and in [44][45][46][47][48][49][50].…”

“…More detailed descriptions and explanations of the MSF model were reported in [45][46][47][48][49][50][51]. Among the MSF model parameters, the constants and coefficients in Equations ( 9)-( 13) for MSF prediction were calculated with reference to the experiment results herein and in [44][45][46][47][48][49][50]. Some material parameters were picked from studies by Torries et al [22] and Ren [23] with similar manufacturing methods and microstructural features.…”