Additive Manufacturing Fatigue and Fracture IV: Toward Confident Use in Critical Applications: Poster Session
Sponsored by: TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Nik Hrabe, National Institute of Standards and Technology; Steve Daniewicz, University of Alabama; Nima Shamsaei, Auburn University; John Lewandowski, Case Western Reserve University; Mohsen Seifi, ASTM International/Case Western Reserve University
Monday 5:30 PM
February 24, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr
Session Chair: Nik Hrabe, National Institute of Standards and Technology
Cancelled
A-1: As the Delamination Fracture Behavior in the AlSi10Mg DMLS Parts Built in Different Orientations: Roberto Seno1; Eder Najar Lopes2; 1CBA; 2Unicamp
Due to its lightweight, hardenability and low powder cost the AlSi10Mg additive manufactured (AM) parts has become a subject of attention in the last years in the automotive and aerospace industries. The aim of this work was to study the fracture mode of the AM samples built in different orientations (parallel and perpendicular to the build plate). Tensile and Crack Tip Opening Displacement results for as-built parallel and perpendicular samples were UTS 425 MPa, YS 266 MPa, elongation 6%, KIC 21 MPa√m, and UTS 401 MPa, YS 206 MPa, elongation 4%, KIC 15 MPa√m, respectively. Stress-relief heat treated samples (300 °C for 2 h) depict UTS 351 MPa, YS 229 MPa, elongation 7%, KIC 24 MPa√m, and UTS 339 MPa, YS 211 MPa, elongation 6%, KIC 16 MPa√m, respectively. Although the heat treatment improves the ductility there was no effect in perpendicular specimens KIC results.
A-4: Effect of Post Heat-treatment on the Microstructure, Tensile and Fatigue Properties of AlSi10Mg Alloy Manufactured by Selective Laser Melting: Tae-Hyun Park1; Min-Seok Baek1; Yongho Sohn2; Kee-Ahn Lee1; 1Inha University; 2University of Central Florida
Microstructure evolution, tensile and high cycle fatigue properties of AlSi10Mg alloys manufactured by selective laser melting were investigated according to two different post heat-treatments. Direct aging (D.A.) and T6 heat treatments were conducted respectively for SLM AlSi10Mg alloys. Regardless of post heat-treatments, AlSi10Mg alloys consisted of α-Al, eutectic Si, AlFeSi intermetallics, and nano-sized precipitates (Mg2Si). Microstructure characteristics such as molten pool, cellular-structure, and precipitates were analyzed quantitatively by OM, FE-SEM, EBSD, and TEM. Yield strengths of as-bulilt, direct-aged, and T6 heat treated alloys were 264MPa, 310MPa and 180MPa, respectively. Tensile strengths of as-built and direct-aged alloys were similar, but higher than that of T6 heat treated alloy. High cycle fatigue results showed that the direct-aged alloy had significaltly higher fatigue property compared to those of as-built and T6 alloys. Fracture surfaces and deformed microstructures were analyzed and the strengthening and fracture mechanisms of SLM built AlSi10Mg alloys were also discussed.
A-6: Fatigue Life Prediction of Additive Manufactured IN718 Superalloys: Wenye Ye1; Pankaj Kumar1; Leslie Mushongera1; 1University of Nevada, Reno
Fatigue failure of additive manufactured columnar polycrystals is often dominated by crack initiation processes, which are strongly influenced inherent defects existing in the microstructure. Internal microstructural defects such as porosity, inclusions, etc. act as stress concentration sites and preferred crack initiation zones during cyclic loading, leading to premature rupture. We use the crystal plasticity finite element approach to analyze the influence of microstructural heterogeneities on the low cycle fatigue of large-grained polycrystals. A set of microstructurally differing statistically equivalent microstructures is subjected to fatigue and crack nucleation and growth, to analyze transgranular and intergranular crack paths in dependence on microstructural characteristics. The morphology and texture characterized using EBSD and Cellular Automata are utilized to construct representative statistically equivalent microstructures. A criterion related to the energy stored in microstructures under deformation is used to predict scatter in fatigue crack nucleation life and the results compared with experimental findings.
A-9: Microstructure, High-temperature Tensile and Fatigue Properties of IN625 Manufactured by Selective Laser Melting: Tae-Hoon Kang1; Kyu-Sik Kim1; Michael Kassner2; Kwang-Tae Son2; Kee-Ahn Lee1; 1Inha University; 2University of Southern California
Microstructure, high-temperature tensile and fatigue properties of additively manufactured IN625 were investigated and compared with (conventional) wrought IN625. To obtain lower defect and uniform microstructure of selective laser melted IN625, the hot-isostatic-pressing (HIP) process was carried out at 1175℃ and 150MPa for 3 hours under Ar gas environment. Initial microstructural characteristics were analyzed by SEM, XRD, EBSD, and TEM. As a result, the SLM IN625 alloy showed to contain nano-sized precipitates (Ni3Nb, TiN). Mechanical properties were evaluated at both room temperature and 650℃. Yield strength difference between SLM IN625 (246.2MPa) and wrought IN625 (242.6MPa) was similar at 650℃. But SLM IN625 showed lower ductility (38.7%) than wrought IN625 (73%). High-temperature fatigue tests were conducted at 650℃. Fatigue limits of both alloys were higher (500MPa for SLM and 550MPa for wrought) than those yield strengths at 650℃. Based on these findings, correlations between microstructure, high-temperature deformation and fatigue mechanisms were discussed.
A-10: Microstructure, Mechanical Properties, and Fatigue Damage Mechanisms in Laser Powder Bed Al-10Si-0.4Mg Alloys: Timothy Piette1; Robert Warren1; Edward Hummelt2; Diana Lados1; 1Worcester Polytechnic Institute; 2Eaton Corporation
Laser powder bed (LPB) manufactured Al-10Si-0.4Mg was studied in as-fabricated, T6, and HIP+T6 conditions, to understand the effects of microstructure and heat treatment on mechanical properties. Tensile and fatigue crack growth (FCG) properties and behavior were compared with those of conventionally-cast counterparts and related to build orientation and post-processing conditions. The as-fabricated LPB alloys show lower FCG response compared to the conventionally-cast and heat treated LPB alloys. Anisotropic residual stresses in the as-fabricated condition affect the FCG thresholds, resulting in differences between build orientations. Heat treatments alter the microstructure, which causes loss of orientation dependence on properties, improves FCG threshold values, and changes the crack growth mechanisms. Fatigue testing in high-cycle fatigue regime was performed to relate the effects of build orientation, heat treatment, surface condition, and defect morphology and distribution (evaluated using x-ray computed tomography) to fatigue life. Recommendations for microstructure and post-processing optimization for fatigue-critical applications are provided.