Additive Manufacturing Fatigue and Fracture V: Processing-Structure-Property Investigations and Application to Qualification: Inconel, New Alloys, and Functional Gradients
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
Tuesday 2:00 PM
March 16, 2021
Room: RM 2
Location: TMS2021 Virtual
Session Chair: Mohsen Seifi, ASTM International/Case Western Reserve University
2:00 PM Invited
Laser Powder Bed Fusion of TiTa Alloys: Process Optimisation and Fatigue Properties: Andrey Molotnikov1; Erin Brodie2; Thomas Niendorf3; 1RMIT University, Centre for Additive Manufacturing; 2Monash University; 3University of Kassel
Additive manufacture is emerging as a viable manufacturing method for fabrication of a new type of β-titanium alloys such as TiTa. However, the addition of refractory element Ta possess some processing challenges due to its very high melting point. In this work, fabrication of multiple TiTa alloys using laser powder bed fusion (L-PBF) is reported. The optimisation of processing parameters to produce fully dense samples with a minimised volume fraction of unmelted Ta particles is discussed focusing on different processing strategies. The produced material and lattice structures were assessed for mechanical properties under static and cyclic loading. TiTa alloy showed similar strength to L-PBF titanium with half the elastic modulus and an altered microstructure caused by the ‘remelt’ scanning strategy. The alloy demonstrated a superior yield stress normalised fatigue performance compared with commercially pure Ti, and Ti-6Al-4V. The morphology of the resulting microstructures was analysed by SEM and XRD analysis.
2:30 PM
Synchrotron Imaging of the Influence of TiB2 in Suppressing Hot Cracking during Laser Powder Bed Fusion of Al-2139: David Rees1; Chu Lun Alex Leung1; Joe Elambasseril2; Sebastian Marussi1; Saurabh Shah1; Shashidhara Marathe3; Milan Brandt2; Mark Easton2; Peter Lee1; 1University College London; 2RMIT University; 3Diamond Light Source Ltd
Al-Cu-Mg-Ag alloys are ideally suited for the production of low volume specialist aerospace components by laser powder bed fusion (LPBF). However, the mechanical performance of these alloys is diminished by a high susceptibility to hot cracking, which may reduce fatigue resistance, leading to premature component fracture. We investigated two processing strategies to suppress hot crack formation by controlling the solidification behaviour and resulting microstructure: (1) TiB2 inoculant additions; and (2) in situ optimisation of the LPBF process parameters. Using high-speed synchrotron X-ray imaging, we monitored the LPBF of Al-2139 with and without the addition of TiB2 for a range of parameters. We also performed synchrotron X-ray microtomography (µCT) and electron microscopy to characterise build features detrimental to fatigue life, such as porosity, cracking, surface roughness, and microstructural inhomogeneity in terms of population, size, morphology, and location. Our results reveal possible methods to reduce crack formation during LPBF of Al-2139.
2:50 PM
Microstructural Heterogeneity and Mechanical Anisotropy of 18Ni-330 Maraging Steel Fabricated by Selective Laser Melting: The Effect of Build Orientation and Height: Yao Yi1; Kaiwen Wang2; Xiaoqing Wang3; Lin Li1; Wenjun Cai2; Samuel Kelly3; Natalia Esparragoza3; Matthew Rosser3; Feng Yan1; 1The University of Alabama; 2Virginia Polytechnic Institute and State University; 3Jacksonville State University
In this study, tensile 18Ni-300 maraging steel samples were fabricated using selective laser melting (SLM) to investigate the effects of built height and orientations on the evolution of the microstructure and the mechanical properties of the samples. The microstructure of the as-fabricated samples consists of primary α-martensite phase and fine cellular microstructure (~ 0.66 - 0.83 μm) with the retained austenite γ-phase aggregated at the boundaries of the cells, resulting in an enhanced mechanical performance compared with traditional counterparts under the same condition (without post-heat treatments). Random grain orientations with weak textures are revealed in all samples. The XY-built samples display better tensile performance when compared to the Z-built samples due to the fine grain sizes and retained γ phase. The bottom of the Z-built sample exhibits a higher hardness than other parts of the sample, which could be attributed to its finer cellular structure.
3:10 PM
Characterization of 3D-printed Metals with Ultrasonic Technique: Terence Costigan1; Ping-Chuan Wang1; Robert Van Pelt2; Aaron Nelson1; 1SUNY New Paltz; 2Sono-Tek Corporation
Additive manufacturing (AM) of metals is rapidly finding applications in various industries, but certain disadvantages inherited in AM prevent it from becoming widely adopted, including surface roughness, lack of isotropic densification and dimension accuracy, etc. Such imperfections have significant impact on product performance and reliability. The goal for this research is to develop a characterization means using ultrasonic excitation to investigate how properties and fatigue behavior of AM parts depend on fabrication factors such as density and printing orientation. A test methodology being developed employs a pair of conical stainless steel specimens with piezoelectric transducers sandwiched in between to induce vibration. In this presentation, feasibility of the test and specimen design will be demonstrated with finite element modeling. Experimental results will be summarized by comparing specimens prepared by AM with several printing conditions and by traditional machining process. The implication of using ultrasonic characterization of AM structures will be discussed.
3:30 PM Invited
Tensile and Fatigue Behavior of Cold Sprayed Material Using Heat Treated Feedstock Powders: Luke Brewer1; A. R. Webb1; Ning Zhu1; J. Brian Jordon1; 1The University of Alabama
This talk will present the impact of feedstock powder heat treatment on the tensile and fatigue properties of cold sprayed AA7075 material. The as-atomized microstructure of gas atomized powders leads to a reduction in deposition efficiency, strength, and ductility in cold sprayed materials; particularly for precipitation hardened alloys. We have produced cold sprayed materials using two types of heat treatment: full solution treatment and overaging. Cold spray deposition using helium gas was used to build samples large enough for multiple tensile and fatigue samples to be produced from cold spray-only materials. The full solution treated samples show a small increase in ductility over the as-atomized powders with a small decrease in yield strength. Overaged powders show a substantial increase in ductility but with a marked decrease in yield strength. In both cases, the heat treatment changes the nature of the fracture surface to one controlled primarily by microvoid coalescence.