Additive Manufacturing: Length-Scale Phenomena in Mechanical Response: Miscellaneous II
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Meysam Haghshenas, University of Toledo; Andrew Birnbaum, Us Naval Research Laboratory; Robert Lancaster, Swansea University; Xinghang Zhang, Purdue University; Aeriel Leonard
Thursday 2:00 PM
March 23, 2023
Room: 23B
Location: SDCC
Session Chair: Robert Lancaster, Swansea University
2:00 PM
Optimization of Post-built Annealing of Ni Alloy718 Processed by Powder Bed Fusion: Jan Capek1; Efthymios Polatidis1; Magnus Niekter2; Joe Kelleher3; Nicola Casati1; Markus Strobl1; 1Paul Scherrer Institute; 2University West; 3ISIS Neutron and Muon Source
Laser powder bed fusion provides valuable prospects for nickel-based superalloys that are used in many applications. However, the microstructure and mechanical properties of these materials are especially sensitive to the manufacturing conditions and post-treatments that are applied to relieve the internal stresses, as they are susceptible to the formation of different types of precipitates, depending on the alloy chemistry, temperature and time.A combination of in situ high-temperature neutron diffraction and synchrotron X-ray diffraction was used to study the evolution of the residual stresses and precipitation in nickel based Alloy 718 for a temperature range from 600°C to 1000°C. Using the Engin-X beamline, ISIS UK, it was possible to follow the evolution of residual stresses. X-Ray diffraction data was used to evaluate the initial phase composition and its evolution during the annealing. These results allow for the optimization of one-step annealing treatments to relieve residual stresses and control the microstructure.
2:20 PM
Scale Effects in Application of Profilometry-based Indentation Plastometry (PIP) to Additively Manufactured Components: Jimmy Campbell1; John Reidy2; Animesh Bose2; Hannah Zhang3; Tony Fry3; Becky Musgrove1; Wenchen Gu1; Bill Clyne1; 1Plastometrex Ltd; 2Desktop Metals; 3National Physical Laboratory
PIP testing (https://doi.org/10.1002/adem.202100437) involves indentation of (metallic) samples, indent profile measurement and iterative FEM simulation, converging on the stress-strain relationship giving optimal agreement between measured and modelled profiles. A key feature is the scale. The deformed region has lateral dimension of ~1 mm and a depth of ~ 100 µm (requiring a load in the kN range). The tested volume is usually “many-grained”, and hence representative of the bulk, whereas most nano-indentation takes place within single grains. A systematic comparison (https://doi.org/10.1002/adem.202001496) has already confirmed the superior reliability of PIP, compared with nano-indentation-based techniques. The current work concerns (isotropic and homogeneous) AM materials, following an earlier PIP-based investigation (https://doi.org/10.2139/ssrn.3746800) into the anisotropy of AM samples. Comparisons are presented between the outcomes of PIP, a nano-indentation-based procedure and conventional tensile testing. It is clearly shown that PIP is particularly well-suited to characterization of AM components.
2:40 PM
Revealing Intragranular Orientation and Strain Evolution during Additive Manufacturing of a Stainless Steel: A Synchrotron X-ray Diffraction Study: Steve Gaudez1; Kouider Abdesselam1; Hakim Gharbi1; Zoltan Hegedues2; Ulrich Lienert2; Wolfgang Pantleon3; Manas Upadhyay1; 1Ecole Polytechnique, LMS, CNRS; 2PETRA III, DESY; 3Technical University of Denmark
During a metal Additive Manufacturing (AM) process, just after deposition, a material undergoes rapid solidification. Then, until the end of the process, it is subjected to Solid-State Thermal Cycling (SSTC). It is important to study the role of SSTC on the microstructure evolution during AM because the microstructural features affected by SSTC such as texture, internal strains, etc., determine the microstructural response. Recently, we have performed High-Resolution Reciprocal Space Mapping (HRRSM) experiments – a synchrotron-based X-ray diffraction technique - to study the role of SSTC on the evolution of intragranular orientation and strain during AM of a 316L stainless steel. The results show a significant change to the internal structure and strain due to SSTC, which will affect the eventual mechanical properties of the sample being built. The results also indirectly prove that the thermodynamic forces generated during SSTC can significantly alter the dislocation structure in the material.
3:00 PM
Combined Effects of Pre-straining and Hydrogenation on the Nanomechanical Behavior of Selectively Laser Melted High-/medium-entropy Alloys: Zhe Gao1; Dong-Hyun Lee2; Yakai Zhao3; A-Hyun Jeon1; Upadrasta Ramamurty3; Jae-il Jang1; 1Hanyang University; 2Chungnam National University; 3Nanyang Technological University
The combined effects of pre-straining and hydrogenation on the nanomechanical behavior of selectively laser melted high-/medium-entropy alloy samples are explored. A series of nanoindentation experiments were performed on the samples that were pre-strained to different levels of strain and then electrochemically hydrogenated. The results were analyzed in comparison with those of conventionally manufactured samples and discussed in terms of the role of pre-strain in the plastic deformation of the face-centered-cubic high-/medium-entropy alloys in both hydrogen-charged and uncharged states.
3:20 PM Break
3:40 PM
A Micropillar Compression Investigation into the Plastic Flow Properties of Additively Manufactured Alloys: Ramamurty Upadrasta1; Shi-hao Li1; 1Nanyang Technological University
The role of Solidification cells and high density of dislocations, common features in alloys processed using laser powder bed fusion (L-PBF) and directed energy deposition (DED), on the plastic properties was investigated via the micropillar compression on 316L stainless steel and the Inconel 718. The variations in the yield strength with the pillar size are similar to those reported on pillars fabricated from pre-strained Ni but are opposite to those reported on pillars of crystalline alloys. The mechanical responses of the pillars with and without cell boundaries (CBs) are similar, which suggests that the high density of dislocations—-and not the CBs—-determine the strength of the AM alloys. Further, results suggest that the dislocation networks significantly enhance dislocation storage, leading to bulk-like deformation behavior and superior work hardening capability in the L-PBF pillars with larger diameters.
4:00 PM
An Efficient Method for the Prediction of Mechanical Properties from the Microstructures of Additively Manufactured Parts: Nathan March1; Dayalan Gunasegaram1; 1CSIRO
The mechanical properties of additively manufactured (AM) parts are of critical importance in determining their suitability for their intended application. Due to the spatial variation in the microstructure of AM parts caused by local cooling rates, AM parts can have anisotropic, location-specific mechanical properties, which cannot be measured efficiently with physical testing. This motivates the need for the prediction of mechanical properties using computational homogenization (CH). CH is a mathematical technique that allows for the calculation of mechanical properties and associated quantities. We discuss the implementation of CH for AM parts implemented with a Fast Fourier Transform-based numerical solution technique. Our results demonstrate the accuracy and efficiency of CH for AM parts allowing for: a reduction in the amount of destructive and expensive physical testing required for qualification and certification; the completion of a missing link in the process-structure-performance relationship in the ICME paradigm; and faster and more efficient builds.
4:20 PM
Investigation of the Mechanical Properties in Additively Manufactured Haynes 230 Alloy with Hierarchical Microstructure: Bo Yang1; Zhongxia Shang1; Jie Ding1; Jack Lopez1; Tianyi Sun1; William Jarosinski2; Yifan Zhang3; Nicholas Richter1; Haiyan Wang1; Xinghang Zhang1; 1Purdue University; 2Praxair Surface Technologies; 3Los Alamos National Laboratory
Laser powder bed fusion (L-PBF) has gained wide attention in the recent years owning its abilities to produce alloys in a near-net-shape manner and to introduce unique microstructure via rapid laser heating and quenching. Haynes 230 is a solid-solution-strengthening nickel-based superalloy with excellent corrosion resistance and high temperature mechanical properties. In this study, well-dispersed M6C carbide precipitates enriched with W and Mo, with an average particle size of ~100 nm, were introduced into Haynes 230 alloy by heat treating the L-PBF processed Haynes 230 alloy with dislocation cell walls. The nano-sized carbides align along <100> directions with an average spacing of 500 nm. The introduction of such structure significantly enhances the work hardening capability of the alloy and alters its deformation mechanism. Mechanical tests in both bulk and micro scales were used to investigate the mechanism for the improved mechanical properties and explore the potential in alloy engineering with L-PBF.