Additive Manufacturing Fatigue and Fracture V: Processing-Structure-Property Investigations and Application to Qualification: Microstructure-based Fatigue Studies on Additive-Manufactured Materials (Jointly Organized with Fatigue in Materials Symposium)
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; John Lewandowski, Case Western Reserve University; Nima Shamsaei, Auburn University; Mohsen Seifi, ASTM International/Case Western Reserve University; Steve Daniewicz, University of Alabama
Wednesday 2:00 PM
March 17, 2021
Room: RM 3
Location: TMS2021 Virtual
Session Chair: Garrett Pataky, Clemson University
2:00 PM Invited
Automotive-specific Requirements for Additive Manufacturing of Metal Materials: Tyson Brown1; Whitney Poling1; 1General Motors
The adoption of metal Additive Manufacturing (AM) throughout many industries – aerospace, medical, prototyping – has seen rapid advancement in the last months and years. Automotive applications for high-performance or racing vehicles can be included in those categories, but several factors have prevented the wider proliferation of metal AM to high-volume or consumer automotive applications. This talk will focus on the material considerations that affect the ability to use metal AM at an automotive scale, highlighting the need for development of new materials and process paths that improve throughput while maintaining high density and fatigue properties. These materials and processes might be considered a specialization of the metal AM market to allow greater adoption by the automotive sector.
2:30 PM
Fatigue Crack Growth and Fracture Toughness Behavior of Laser Powder Bed Fusion Titanium Alloys: Jamie Kruzic1; Tarik Hasib1; Xiaopeng Li1; 1University of New South Wales
Laser powder bed fusion (LPBF) produces unique microstructures (e.g., columnar grains, texture, etc.) that influence mechanical properties. In this work, the crack growth properties of LPBF produced CP-Ti and Ti-6Al-4V were examined at room temperature with various cracking orientations relative to the build plane and various post heat treatments, including hot isostatic pressing (HIP). Both materials showed negligible anisotropy in their fatigue growth rates and thresholds, especially when compared to a commercially produced wrought CP-Ti plate that showed large anisotropy in its fatigue threshold. Generally, the fatigue thresholds were defined by the ability to transfer slip from one α'/α lath to another, with a minor role of roughness induced crack closure. Fracture toughness results for the LPBF produced CP-Ti showed increased anisotropy compared to the fatigue thresholds. Microstructure analysis, fractography, and crack profiles were used to further understand the microstructure influence on the fracture and fatigue crack growth properties.
2:50 PM
Fatigue Crack Growth Rate of Electron Beam Melted (EBM) Titanium Alloy (Ti-6Al-4V): Effect of Crystallographic Texture and Internal Porosity: Nik Hrabe1; Jake Benzing1; Nick Derimow1; Tim Quinn1; Jolene Splett1; Lucas Koepke1; 1National Institute of Standards and Technology
The effects of crystallographic texture and internal pores on ASTM E647 fatigue crack growth rate (R = 0.1) of EBM Ti-6Al-4V were investigated by studying material in the as-built and HIPed conditions as well as in two orthogonal crack growth directions with respect to the build direction. HIPing sufficiently reduced porosity (x-ray CT), and unexpected texture variation (EBSD) was observed for this material (i.e. NOT <100>β-fiber in the build direction). Significant effect on threshold behavior and the onset of unstable crack growth was observed due to internal porosity and texture variation.
3:10 PM
Laser Powder Bed Fusion of Hydride-dehydride Ti-6Al-4V Powders: Effect of Hot Isostatic Pressing on Microstructure and Mechanical Properties: Mohammadreza Asherloo1; Ziheng Wu2; Srujana Rao Yarasi2; Muktesh Paliwal3; Mike Marucci3; Joe Capone4; Anthony Rollett2; Amir Mostafaei1; 1Illinois Institute of Technology; 2Carnegie Mellon University; 3Kymera International - Reading Alloys; 4Ametek Inc.
In powder bed additive manufacturing, it is assumed that spherical powder results in a desirable powder flowability and higher powder bed packing density. Here, we demonstrate that the bulk flow energy of hydride-dehydride (HDH) Ti-6Al-4V powder with a particle size of 50-120 μm is 341 mJ, while it is 384 mJ for spherical powder with a particle size of 20-63 μm. Laser powder bed fusion process is used to study process window (laser power-velocity) in which a relative density of > 99.5% is achieved. Selected coupons are post heat-treated via hot isostatic pressing to pinch off remnant pores. Microstructure at the cross-sections is studied by optical and scanning electron microscopies to measure solid volume fraction and study pore morphology. Synchrotron-based dynamic x-ray radiography is used to visualize real-time laser-powder interaction and possible defect formation. Mechanical performance (tensile strength, elongation and fatigue life) of the as-built and heat-treated parts are evaluated.
3:30 PM
Towards Validation for Computed Tomography Processes for Additive Manufacturing: Griffin Jones1; Jayme Keist1; Rachel Reed2; Veeraraghavan Sundar2; 1The Pennsylvania State University; 2UES Inc.
Reliable non-destructive evaluation (NDE) techniques are essential in advancing the use of additive manufacturing (AM) to reliably produce critical components. Recent studies have identified resolution limitations to X-ray computed tomography (CT), especially when denser materials are involved. In this study, we present initial results of an effort to establish comparison methods and workflows for validating CT and potentially other NDE methods, with ground truth data from automated serial sectioning on a series of AM components. An automatic defect recognition (ADR) algorithm is used to enhance efficiency of inspection with the CT process. The data was used to evaluate the effectiveness of CT at detecting AM processing flaws. CT, under certain acquisition parameters, can have a lower (<=10%) detection rate compared to that of serial sectioning. The results highlight the need for validation and resolution improvement of NDE methods in critical AM components.