Additive Manufacturing Fatigue and Fracture: Effects of Surface Roughness, Residual Stress, and Environment: Session VII
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; Steve Daniewicz, University of Alabama; Mohsen Seifi, ASTM International/Case Western Reserve University
Thursday 2:00 PM
March 23, 2023
Room: 22
Location: SDCC
Session Chair: Dillon Watring, National Science Foundation
2:00 PM Invited
Process-structure-property Relationships of Additively Manufactured Materials: Challenges and Opportunities: Pooriya Nezhadfar1; 1GE Aviation
There are still challenges associated with additive manufacturing (AM) decelerating its adoption to various industrial sectors for fabricating parts being deployed in fatigue critical applications. This is attributed to the process-induced defects, i.e., residual stress, surface roughness, and volumetric defects, which deteriorate the fatigue and fracture of AM materials. There are also challenges to regulate the source of variabilities in AM; the above-mentioned defects can vary from AM technique-to-AM technique, machine-to-machine, and even build-to-build for a single material system. Accordingly, it is essential to understand the process-structure-property (PSP) relationships of additively manufactured materials. There have been efforts conducted by research organizations and industrial corporations to enhance the fatigue performance of materials via feedstock optimization, process parameter modification, and post-process treatments (i.e., thermal heat treatment, surface treatment). This talk aims to review the PSP relationships for various AM materials, challenges, and possible opportunities to enhance fatigue performance of AM materials.
2:30 PM
High Cycle Fatigue Properties of Laser Metal Deposited Waspaloy: Romain Bordas1; Jonathan Cormier1; Patrick Villechaise1; Azdine Nait-Ali1; André Malié2; Alice Cervellon2; Roland Fortunier3; 1Ensma - Institut Pprime - Upr Cnrs 3346; 2Safran Aircraft Engines; 3LTDS, école centrale Lyon / ENISE, on secondment to ENSMA
Two different sets of manufacturing parameters were tested to produce two batches of LMD-processed Waspaloy specimens : one with a significant amount of porosity and another with a low amount. Then, HCF tests were performed at 700 °C, 80 Hz and with a stress ratio of 0.05, the maximum applied stress ranging from 50 % to 90 % of the Yield Stress. One single trend has been identified from the S-N diagram regardless of the porosity characteristics. However, two types of crack initiation mechanism have been observed: crack initiation at large sub-surface pores inherited from the LMD process and crack initiation with a crystallographic facet. In both cases, a crystallographic crack propagation from the crack initiation site has been observed whatever the localisation and nature of the initiation site. In this presentation, a special focus will be paid to the first stage of crack propagation from the critical sites.
2:50 PM
Comparison of Fatigue Properties, Fractography, and Microstructures of Laser Powder Bed Fusion Al 6XRAM2, 7XRAM2, and 7A77 Aluminum Alloys: Teri Juarez1; Molly Hwang1; Bryan McEnerney1; 1NASA JPL
Advanced aluminums are of significant interest in the design and implementation of robotic spaceflight hardware. A critical factor for a number of systems is the fatigue response, which has not been studied in-depth in these advanced aluminums. The fatigue behavior, microstructure, and fractography of Al 6XRAM2, Al 7XRAM2, and Al 7A77, produced via laser powder bed fusion were investigated, and compared to their wrought analogues. Fatigue testing was performed at 60 Hz, with a R = -1 value at 50% of yield strength, at room temperature, based upon empirical data. The fatigue behaviors and fracture morphology will be discussed, as well as some discussion of the potential root cause of the variation seen from the wrought alloys.
3:10 PM
CuCrZr Processed by Laser-Based Powder Bed Fusion - Processability and Influence of Heat Treatment on Electrical Conductivity, Microstructure and Mechanical properties: Thomas Wegener1; Julian Koopmann2; Julia Richter1; Philipp Krooß1; Thomas Niendorf1; 1University of Kassel; 2Group Research, Volkswagen AG
Due to outstanding properties copper (Cu) and Cu alloys represent one of the major groups of commercial metals with respect to production and consumption. However, the low strength of copper is referred to as the main drawback. CuCrZr represents a candidate to satisfy strength limitations by aging heat-treatments. Conventional manufacturing becomes extremely challenging when machining of complex components is required. Identification of processing routes, such as Laser-Based Powder Bed Fusion (PBF-LB), can be seen as a crucial step towards time and cost efficient production of CuCrZr.The current study focusses on the influence of heat treatments on microstructure and mechanical properties, especially in the low-cycle-fatigue regime, of CuCrZr processed by PBF-LB. Results are discussed based on microstructural investigations (SEM and CT)and on fracture surface analysis, providing novel insights on the role of geometrical parameters to the process window allowing for robust and reliable establishment of solid structures.
3:30 PM Break
3:50 PM
Development of Post-process Heat Treatments Strategy for an Additively Ti-B2 Reinforced AlCu Alloy: Francesco Careri1; Raja Khan2; Moataz Attallah1; 1University of Birmingham; 2TWI Ltd
This work aims to develop a novel customised Heat Treatment for an AlCu-TiB2 alloy (A205) processed using Laser Powder Bed Fusion, and to assess the influence on the microstructural and mechanical properties. In particular, the influence of standard and novel Heat treatment strategies on cast and as-deposited material was assessed through different advanced investigation methods (e.g. fatigue, creep) to evaluate the differences between the traditional and novel manufacturing techniques of High-strength aluminium alloys. Calorimetric studies and electron microscopy were performed to understand the ageing kinetics of the alloy system. Simple ageing simulations were developed to rationalise the ageing behaviour.
4:10 PM
Capturing Cracking during Blown Powder Additive Manufacturing Using Correlative Synchrotron X-ray and IR Imaging: David Rees1; Tristan Fleming2; Xianqiang Fan1; Yuze Huang3; Imogen Cowley1; Sebastian Marussi1; Robert Atwood4; Martyn Jones5; Ben Saunders5; Cu Lun Alex Leung1; Peter Lee1; 1University College London; 2Queen's University; 3Coventry University; 4Diamond Light Source Ltd; 5Rolls-Royce plc
Directed energy deposition (DED) of high gamma prime Ni-superalloys enables the fabrication and repair of complex safety-critical aerospace components. However, these materials are susceptible to hot cracking during DED due to extreme thermal gradients and fast solidification rates. The underlying mechanisms and strategies for cracking mitigation are unclear due to difficulties observing the problem as it occurs. Therefore, we used our bespoke DED process replicator to study the development of hot cracking, using high-speed synchrotron X-ray radiography and correlative infrared (IR) imaging. Our results show hot cracking in real time during DED of CM247LC and 718Plus, with cracking localized to seeded valleys in pre-built samples. We see when cracking occurs in relation to the number of layers built and the position of the molten pool, how crack propagation accelerates with subsequent processing, and the morphology of crack from initiation to completion of the build, along with the accompanying thermal history.
4:30 PM
Residual Stress Induced Fracture of As-Fabricated Laser Powder Bed Fusion Parts: Albert To1; Hai Tran1; 1University of Pittsburgh
Residual stress is believed to be the main cause of cracking of a part during the build process of laser powder bed fusion. A systematic investigation on the residual stress-induced cracking issue is presented. Simulations based on the modified inherent strain method and experiments were used to investigate the residual stress and fracture in Inconel 718 parts manufactured by laser powder bed fusion (L-PBF). The results show that the modified inherent strain method can accurately predict the residual stress, and together with the J-integral approach, fracture can also be predicted with good accuracy. This model is also being applied to simulate crack delamination at the solid/support interface in additively manufactured parts. The results of this work may shed light on the cracking issue in components processed by laser powder bed fusion (L-PBF).
4:50 PM Cancelled
Surface Roughness Measurements of Laser Deposited AlCoCrFeNiTi and AlCoCrFeNiCu High Entropy Alloys for Aerospace Applications: Modupeola Dada1; Patricia Popoola1; 1Tshwane University of Technology
Investigating the surface roughness of metals in the field of precision engineering is vital because surface roughness explains if there are any irregularities on the surface of the as-built aerospace components, which can be nucleation sites for corrosion. In this study, AlCoCrFeNiTi and AlCoCrFeNiCu high entropy alloys were produced via laser metal deposition and the comparative study of two surface roughness (Ra) measuring instruments were used; Gwydion software and a stylus Profilometer. The results showed that the AlCoCrFeNiTi HEA had a higher degree of surface roughness variation; hence, a rougher surface than the AlCoCrFeNiCu HEA, however, the 3D plots and data analysis showed the AlCoCrFeNiCu HEA had more texture. This study also showed that the surface measurements taken from the stylus Profilometer were comparable and in good correlation with the statistical analysis.