Additive Manufacturing Benchmarks 2022 (AM-Bench 2022): Residual Strain/Stress and Distortion III
Program Organizers: Brandon Lane, National Institute of Standards and Technology; Lyle Levine, National Institute of Standards and Technology
Wednesday 1:30 PM
August 17, 2022
Room: Cabinet/Judiciary Suite
Location: Hyatt Regency Bethesda
Session Chair: Thien Phan, Lawrence Livermore National Laboratory
1:30 PM Invited
In-situ Heat Treatment of Additively Manufactured Ti-6Al-4V: Donald Brown1; Maria Strantza2; M Rafailov3; Eloisa Zepeda-Alarcon1; Darren Pagan4; 1Los Alamos National Laboratory; 2Lawrence Livermore National Laboratory; 3Nuclear Research Center; 4Cornell University
Additive Manufacture offers reductions in cost and waste in the production of metallic components as well as the ability to create optimized topologies that are not achievable through conventional manufacturing. To date, few AM components have been qualified for high-consequence structural applications because of insufficient knowledge of the process/structure/property relationship. AM Ti64 has received attention because of the high material cost and the innate ability of AM to minimize material waste. The much higher cooling rates associated with AM result in distinct and metastable microstructures and, subsequently, distinct material properties compared to conventional components. AM Ti64 components are usually heat treated to drive the as-built microstructure closer to a wrought equivalent in microstructure and properties. We have collected diffraction data during heat-treating of AM Ti64 to monitor the microstructural evolution. The evolution of the phase fraction, texture, internal stress and dislocation density during heat treatment will be presented.
2:00 PM
Design for Printing Success Using Additive Manufacturing Process Simulation: Xueyong Qu1; Jacob Rome1; Glenn Bean1; 1The Aerospace Corporation
Additive manufacturing (AM) can make parts with sophisticated geometry to exploit design and manufacturing freedom. The powder bed fusion AM process has unique printing failure modes, such as the recoater blade colliding with an unfinished part. AM process simulation (AMPS) uses finite element analysis to predict residual stress and distortion during the printing process. AMPS is utilized to evaluate severity of recoater blade collision for an aluminum bi-axial fatigue test coupon. Initial design had a high chance of recoater blade collision, even while following existing guidelines for the overhang angle. Prediction from AMPS is used to modify the design to improve the probability of printing success. It was found that reducing printing height, increasing overhang angle, and adding support structures significantly reduced the probability of blade collision. The modified design was printed without failure. The iterative design process, AMPS results, and calibration of AMPS simulation will be presented.
2:20 PM
(On-Demand) The Effect of Heat Input on Residual Stress Buildup in Selective Laser Melting of Ti6AL4V: Londiwe Motibane1; 1CSIR
Residual stress in Selective Laser Melting is affected by several process parameters. High-speed Selective Laser Melting uses a high laser power to achieve fast scanning and therefore high heat input (laser power/laser scanning speed). In most commercial systems, lower heat inputs are attained in comparison. The residual stress build-up in both high heat-input and low heat-input systems was quantified to benchmark the residual stress in high-speed selective laser melting. Cantilever specimen deflections were similar with a spread of approximately l = 3.5mm. The very near surface stresses measured by XRD were much higher for high-speed SLM while the stress distribution as you move away from the very near surface up to 0,8mm in depth measured by hole-drilling, were similar for high heat-input and low heat-input SLM systems. The effect of heat input was found more apparent in the very near top surfaces and not as much in bulk stresses.
2:40 PM
(On Demand) Computationally Derived Correlations Between Segregation, Microstructure Variations and Process-induced Cracks in AM: Chizhou Fang; Hector Basoalto1; Magnus Anderson1; Yu Lu2; Prashant Jadhav1; Sourabh Supanekar2; Mohammad Ahmed2; 1University of Sheffield; 2University of Birmingham
A multiscale materials modelling framework for selective laser melting (SLM) of precipitate strengthened nickel-based superalloys is presented. The approach accounts for physical phenomena over a number of length and temporal scales associated with solid-liquid-vapour transitions, solidification microstructures (grains and precipitation of γ′) and defects, as well as the development of residual stress states. Numerical simulations of the emerging microstructure and properties as a function of process parameters are presented with a high γ′ volume fraction superalloy. Correlations between processing conditions and failure are explored through assessing the predicted chemical segregation and the mechanical driving forces acting on grain boundaries using crystal plasticity. From the numerical solutions of the microstructure, composition and mechanical fields correlations for process induced conditions are established. The model predictions are compared with available experimental characterisation of AM builds, and show reasonable agreement.