Additive Manufacturing: Length-Scale Phenomena in Mechanical Response: Small Scale Mechanical Testing/Microstructural Features I
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
Monday 8:30 AM
March 20, 2023
Room: 23B
Location: SDCC
Session Chair: Meysam Haghshenas, University of Toledo
8:30 AM Introductory Comments
8:35 AM Invited
Estimating Bulk Uniaxial Mechanical Properties of AM Alloys with Instrumented Indentation: Berkovich Hardness, Spherical Stress-Strain Curves, and Small Punch Testing: Jordan Weaver1; 1National Institute of Standards and Technology
Advanced indentation testing provides high-throughput, location specific mechanical property measurements. This is critical for additive manufacturing, which requires rapid characterization tools to speed the development of new processes and materials and local characterization tools to quantify location specific process-structure-property relationships that frequently exist in AM parts. Three types of indentation tests (Berkovich micro-indentation, spherical micro-indentation, and small punch testing) were used on a variety of AM alloys with varying microstructures. The results are critically compared against tensile properties. A framework for high-throughput experiments will be discussed along with measurement science needs for advanced indentation testing characterization of AM alloys.
8:55 AM
An Indentation Study of Mechanical Properties of Laser Powder-Bed-Fusion Fabricated Stainless Steels: Yu-Keng Lin1; Alberico Talignani1; Raj Sanjaykumar Patel2; Roger Qiu3; Kelvin Xie2; Jenn-Ming Yang1; Yinmin (Morris) Wang1; 1University of California, Los Angeles; 2Texas A&M University; 3Lawrence Livermore National Laboratory
Steep thermal gradient and high cooling rate of laser powder-bed-fusion processes engender highly non-equilibrium microstructures. Due to the complexity of the heating-cooling cycles, the microstructure of additively manufactured stainless steels is highly inhomogeneous. In this work, the micro/nano-indentation testing and microstructural characterizations were performed to probe the location-specific features and their correlations with the resultant mechanical properties of 316L stainless steel fabricated by laser powder-bed-fusion (L-PBF). The study revealed strong location-dependent mechanical properties and gained new insights on the variations of microstructures and mechanical properties within a part fabricated by L-PBF. We expect that these results will help improve the additive manufacturing design for future applications. The work at LLNL was performed under the auspices of the US Department of Energy under Contract No. DE-AC52-07NA27344.
9:15 AM Invited
Nanomechanical and Microstructural Characterization of Additively Manufactured Parts Fabricated via High-velocity Laser Accelerated Deposition: Keivan Davami1; Nicholas Brooks1; 1University of Alabama
A novel additive manufacturing technique called High-Velocity Laser Accelerated Deposition (HVLAD) where thin films of material are bonded together layer-by-layer using a high intensity laser is reported. This method is a non-fusion-based technique and does not rely on the thermal effects of laser, rather it uses its mechanical effects similar to the laser peening process. The laser beam is used to generate a pressure wave to accelerate the films, layer-by-layer, with a high velocity towards a substrate to create a bond. This process is repeated until a desired thickness, or a three-dimensional object is created. Nanomechanical characterization techniques are used to evaluate the mechanical properties of the deposited material as well as the substrate. Scanning electron microscopy is used to investigate the microstructure. A correlation is drawn between the microstructure and mechanical properties. The HVLAD method is capable of depositing a wide range of materials.
9:35 AM
Nanoindentation Assisted Measurements of Hierarchical Mechanical Properties in Additively Manufactured Martensitic Steel: Ankita Roy1; Abhijeet Dhal1; BA McWilliams1; Kyu C Cho1; Clara M Mock1; Rajiv Mishra1; 1University of North Texas
Construction of spatial heterogeneity guide maps provide effective guidance regarding mechanical behavior of additively manufactured materials. High resolution measurements of micromechanical properties become an integral part of the studies in additive manufacturing since the mechanical behavior of the individual nano scale phases are responsible for determining the overall mechanical response of the material. Thus, the characterization and quantification of these constituent phases hold the answer to the overall property improvement, calibration, and quality certification of any additively manufactured alloy. In this research a high throughput nanoindentation method for such measurements has been proposed at multiple scales which can be extrapolated to deduce the overall mechanical behavior of additively manufactured alloys. Various aspects and characteristics of the nanoindentation curves are carefully interpreted to extract information about the micromechanical response at various length scale.
9:55 AM Invited
Nanoindentation Response of Wire-arc Additive Manufactured and Friction Stir Modified Cu-Al-Ni Alloy: Farzad Khodabakhshi1; Adrian P. Gerlich1; Mohsen Mohammadi2; 1University of Waterloo; 2University of New Brunswick
Friction stir processing (FSP) technology was implemented to modify the microstructure of wire-arc additive manufactured (WAAM) nickel-aluminum bronze (Cu-Al-Ni) alloy and correspondingly improve its functional properties for possible marine applications. To this end, the localized mechanical response of stirred regions processed under various parameters was evaluated using micro-mechanical characterization based on nanoindentation experiments. Then, the incipient plasticity behaviors and strength trends are discussed in correlation with the microstructural features of the stir zone (SZ) at different processing parameters concerning the alloy's primary WAAM state.
10:15 AM Break
10:35 AM Invited
The Effect of Nano-scale Porosity on the SCC Behavior of AM 17-4PH in the Peak- and Over-aged Condition: James Burns1; Trevor Shoemaker1; Zach Harris1; 1University of Virginia
Recent work has shown increased SCC susceptibility in AM 17-4PH when compared to its wrought equivalent. In particular, AM crack growth rates were shown to be up to five-times faster than wrought 17-4PH under cathodic electrochemical potentials. These differences are evaluated in the context of a micro-mechanical damage model that links the sensitivity of the local crack dip damage evolution to the underlying microstructural features. This analysis paradigm enables an unambiguous investigation of the role of AM specific microstructures on the resulting macroscale engineering properties. This presentation will focus on the important impact of nano-scale porosity on the SCC susceptibility and how the sensitivity of these features vary between a peak-age (H900) and overaged (H1025) temper. The results from this work are intended to rigorously identify microstructural features leading to deficiencies in AM 17-4PH SCC behavior so that they may be targeted for amelioration in future AM processing modifications.
10:55 AM
Length Scale Effects of Nanoindentation on Additively Manufactured Stainless Steel: Kunqing Ding1; Yin Zhang1; Andrew Birnbaum2; John Michopoulos2; David McDowell1; Ting Zhu1; 1Georgia Institute of Technology; 2US Naval Research Laboratory
Additively manufactured (AM) metallic materials often exhibit superior yield strength and strain hardening due to printing-induced sub-micron dislocation cell structures. Nanoindentation is recently used to probe the mechanical properties of both printed layers and stainless steel base plate with and without annealing treatment. We perform gradient plasticity finite element (GPFE) simulations to capture the nanoindentation size effect. GPFE simulations also enable us to approximately extract the uniaxial stress-strain behavior of printed layers and base plates from their nanoindentation responses at large indenter depths. Our results indicate that printing-induced dislocation cells play a significant role in the nanoindentation responses in both size dependent and independent regimes. This work underscores the interplay of length scale effects due to nanoindentation and printing-induced microstructure.
11:15 AM Invited
Micromechanical Testing of Additively Manufactured Materials and Structures: Opportunities for a Better Understanding of the Structure-Property Relationships: Sezer Ozerinc1; 1Middle East Technical University
With the recent advances in force & displacement sensing technology and instrumentation, micromechanical testing has become a powerful tool to investigate mechanical behavior at the small scale. Micromechanics, originally focused on the testing of small-scale materials, is finding a wider range of applications in probing bulk materials’ mechanical behavior. Additively manufactured materials and structures exhibit complicated microstructures, including heterogeneities, anisotropic features, interfaces, and gradients. The length scales of these vary from micro- to nanoscale, rendering micromechanical testing an excellent tool to probe the associated mechanical behavior.In this talk, I will give an overview of our recent work and the progress in the micromechanics community that enables effective characterization of the mechanical properties at the small scale, and I will discuss the implications of these advancements for additive manufacturing research.