Additive Manufacturing: Nano/Micro-mechanics and Length-scale Phenomena: Defects and Damage/Deformation Mechanisms and Mechanical Properties
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Meysam Haghshenas, University of Toledo; Robert Lancaster, Swansea University; Andrew Birnbaum, Us Naval Research Laboratory; Jordan Weaver, National Institute Of Standards And Technology; Aeriel Murphy-Leonard, Ohio State University
Thursday 8:30 AM
March 3, 2022
Room: 260A
Location: Anaheim Convention Center
Session Chair: Robert Lancaster, Swansea University; Jordan Weaver, National Institute Of Standards And Technology
8:30 AM
Deciphering the Fundamental Cause of Shape Distortion in Sintering-based Additive and Non-additive Manufacturing Processes: Sandra Ritchie1; Sasa Kovacevic1; Prith Deshmukh1; Sinisa Mesarovic1; Rahul Panat1; 1Carnegie Mellon University
Sintering of nano and/or microparticles is a critical step in many advanced manufacturing processes. Particle consolidation and sintering has been shown to result in shape distortion. Using aerosol jet printing to create various freestanding structures of assembled nanoparticles, we study the mechanisms of shape distortion and developed a model to explain and predict this behavior. Experimental results show that those structures exhibit measurable distortion in the form of permanent curvature upon sintering (with no porosity gradients), indicating mass transport. We hypothesize that temperature difference causes an uneven onset of sintering and shrinkage, which induces mass transport in the direction of the thermal gradient, effectively lengthening areas which heat more slowly. A macroscopic continuum model is developed for nonhomogeneous sintering. The computational results show a remarkable agreement with experiments. Parameters fitted to a series of experiments on the same powder, with different geometries and temperature gradients, exhibit numerical consistency
8:50 AM
Mechanical Properties of Tantalum Cold Sprayed Deposits: Insight Into the Interstitial Hydrogen Content and Powder Size Distribution Effects: Mahsa Amiri1; Kliah Soto Leytan1; Daniel R. Mumm1; Lorenzo Valdevit1; 1University of California, Irvine
Experimental and computational approaches were utilized to understand the influence of interstitial hydrogen in particle deformation, jetting and metallurgical bonding, and mechanical properties of cold-sprayed coatings of tantalum. Micro-tensile and micro-compression samples were extracted from particles of powder-feedstocks with different hydrogen contents and particle sizes, as well as from localized regions of sprayed coatings. SEM and HRTEM were used to analyze the microstructures of the coatings and deformed micro-test samples. The deformation of tantalum with varying H contents was studied via molecular-dynamics simulations, at strain rates representative of those expected during the cold-spray impact. The results suggest that low H contents does not cause embrittlement or significant deterioration of mechanical properties. The different behaviors observed in micro-mechanical tests of the coatings are instead attributed to the quality of bonding at the inter-splat boundaries and differences in the network of defects in the coatings resulting from different particle sizes, oxide nature and thickness.
9:10 AM Cancelled
Deformation Mechanism of Selective Laser Melted 316L Stainless Steel and Its Cellular Substructure Dependence: Feng He1; 1State Key Laboratory of Solidification Processing
The selective laser melted (SLM) 316L stainless steel (316L SS) has shown superior tensile ductility and doubled yield strength compared to its wrought counterpart. The significantly improved yield strength has been attributed to the unique cellular substructures that are featured by Cr/Mo-segregation and trapped dislocations. However, the excellent tensile ductility was still vaguely ascribed to pronounced deformation twinning without clear reasons. The effect of cellular substructure on the deformation mechanism also remains unrevealed. In the present study, we investigated the deformation mechanism of the SLM 316L SS using comprehensive transmission electron microscope (TEM) analysis. Besides active deformation twinning, deformation faulting and dislocation cell refinement were also featured during the whole tensile deformation. Deformation faulting and dislocation cell refinement synergistically dominate the deformation behavior at low strain levels, and deformation twinning and faulting play a crucial role at medium and high strain levels. The cellular substructure dependence was also discussed.
9:30 AM
Capturing the Effects of Grain Boundaries and Intersplat Boundaries on Deformation Behavior of Cold Sprayed Components: Yubraj Paudel1; Ryan Cochran1; Shiraz Mujahid1; Kyle Considine1; Hongjoo Rhee1; 1Mississippi State University
Cold spraying is a solid-state deposition process at a lower than melting temperature that can produce nanostructured coatings with negligible grain growth, wrought-like microstructure, near-theoretical density, and minimal compressive residual stresses. Microstructural characterization of cold sprayed Al6061 alloy showed a grain distribution with smaller grains across the intersplat boundary region and larger grains within the powder particles. In this work, full-field crystal plasticity fast-Fourier transform (CPFFT) simulation was used to understand the effects of such grain topology on deformation behavior of cold sprayed components. The study showed the differences in deformation behavior across the substrate-powder boundary, intersplat boundary, as well as within a powder particle. The simulation results were also compared with the deformation behavior of rolled Al6061 alloy.
9:50 AM Break
10:10 AM
Probing Heterogenous Mechanical Properties in AM Materials Due to Melt Pool Boundaries: John Fite1; Timothy Weihs2; John Slotwinski1; Suhas Eswarappa Prameela2; 1JHU Applied Physics Lab; 2Johns Hopkins University
Powder Bed Fusion (PBF) is an additive manufacturing (AM) process capable of producing metal parts with a wide variety of complex and intricate components. AM parts are often treated as uniform bulk materials, however, our initial results on AlSi10Mg suggest that AM parts may in some ways resemble a composite material where different microstructural regions- corresponding to the melt pool boundaries in laser AM parts- each have unique local mechanical properties. We perform in-situ SEM microtensile experiments to measure ductility and tensile strength for AlSi10Mg samples. Microstructural differences of melt pools are correlated to tradeoffs in mechanical properties and deformation mechanisms.
10:30 AM
Hardening Rate Dependent Deformation Behavior of Additively Manufactured Inconel 718 during Nano-scratch: Mustafa Rifat1; Saurabh Basu1; 1Pennsylvania State Unversity
In the present study, the effect homogenization and solution annealing heat treatment on the deformation behavior of Direct Metal Laser Sintered Inconel 718 during nano-scratching is investigated. Two samples- one as-printed and another heat treated were nano-scratched using 1mN and 2mN loads, respectively, ensuring similar scratch depths. Electron Backscattered Diffraction (EBSD) and Atomic Force Microscopy (AFM) were implemented to characterize the microstructure and scratch profile, respectively. Subsequently, a scale-free isotropic finite element framework was used to extract the strain tensor with which Taylor factor of various grains in nano-scratch-like deformation was calculated. Using this information, the influence of hardening rate on pileup formation during nano-scratch was analyzed. These preliminary results suggest a strong influence of dislocation escape from surface as a contributing mechanism towards pileup formation during nano-scratch.