Additive Manufacturing: Nano/Micro-mechanics and Length-scale Phenomena: Small Scale Mechanical Testing/Microstructural Features I
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

Tuesday 2:30 PM
March 1, 2022
Room: 260A
Location: Anaheim Convention Center

Session Chair: Meysam Haghshenas, University of Toledo; Joy Gockel, Colorado School of Mines

2:30 PM Introductory Comments

2:35 PM  
High-throughput Synthesis and Testing of Novel Alloys for Additive Manufacturing: Madelyn Madrigal-Camacho1; Kendrick Mensink1; Guillermo Aguilar1; Suveen Mathaudhu1; 1University of California-Riverside
    The development of alloys for additive manufacturing often concentrates on minor variations to existing alloys created for cast or forged applications, without fully considering the thermo-mechanical processing conditions unique to 3D printing methods. At the same time, the size, scale and control limitations of typical machines prevents high throughput development and testing of alloys. In this talk, we present preliminary results on the use of conventional ball-milling equipment for alloy development, simple lasers for powder sintering, and nanomechanical characterization to project full-scale properties. Preliminary examples of this approach will be presented for conventional AM alloy compositions along with novel nanocrystalline alloy printed materials.

2:55 PM  
Bridging the Deformation Length-scales in Additively Manufactured Metals via In Situ Mechanical Testing: Yinmin (Morris) Wang1; 1University of California, Los Angeles
    Additive manufactured (AM) metals such as 316L stainless steels and Ti-6Al-4V (Ti64) alloys often have microstructural length-scales that span several orders of magnitude. It is thus of tremendous challenge to understand the deformation behavior of these materials at multiple length-scales. This presentation will report our recent effort to explore the deformation mechanisms of two commonly studied AM alloys (316L and Ti64), via in situ synchrotron x-ray diffraction mechanical testing. The influences of micro-residual stresses and porosities on tensile behavior are investigated. We discuss the implications of these results to the practical applications of these materials, and elaborate mitigation strategies to these issues encountered in laser power-bed-fusion additive manufacturing.

3:15 PM  
What Can We Learn from Micromechanical Testing: A Case Study for EBM-produced Ti-6Al-4V: Sezer Ozerinc1; 1Middle East Technical University
    Micromechanical testing, an approach that has been mostly limited to nanoindentation in the 1990s, now consists of numerous powerful tools applicable to a wide range of materials and structures. Micropillar compression and cantilever bending experiments are just two examples among many recently developed techniques, which have enabled direct measurements of fundamental mechanical properties such as yield strength and fracture toughness at the nanoscale. The implications of nanomechanical testing for additive manufacturing (AM) are twofold. Firstly, mapping-based approaches can probe the changes in local mechanical properties due to variations in processing conditions and thermal history, especially in the build direction. Secondly, AM-produced alloys' microstructure is often different from the conventionally manufactured counterparts, and small-scale testing provides insight into the associated structure-property relationships. This presentation provides an overview of some recent findings on these matters, with an emphasis on our recent work on Ti-6Al-4V parts produced by electron beam melting.

3:35 PM  
The Effect of Microstructural Features on the Mechanical Properties of Additively Manufactured Metals and Alloys: Ajit Achuthan1; 1Clarkson University
    The additive manufacturing (AM) technologies of metals and alloys produce highly heterogeneous microstructures consisting of grains and subgrain features of various characteristic length scales. This is due to the relatively high cooling rates of AM. Thus, AM offers a unique opportunity to generate optimal microstructures that produce desirable sets of local mechanical properties. Leveraging this opportunity requires the development of a better understanding of the process-microstructure-properties relationship. In this talk, we present recent advances made in understanding the effect of microstructural features on mechanical properties of additively manufactured metals and alloys. We specifically discuss the effect of cellular subgrain features of 316L stainless and the lamellar subgrain features of Ti6Al4V formed in direct energy deposition (DED) AM. New insights gained from an in-situ characterization study of the deformation at microscopic length scale and the development of constitutive models that account for the effect of cellular subgrain features will be presented.

3:55 PM Break

4:15 PM  
NOW ON-DEMAND ONLY - Effect of Cr Addition on the Microstructure and Mechanical Properties of Additively Manufactured GRCop-84: Ajay Bhagavatam1; Husam Alrehaili1; Guru Dinda2; Golam Newaz1; 1Wayne State University; 2Savannah River National Laboratory
    GRCop-84 (Cu-8Cr-4Nb) offers potential for high-heat-flux applications and is designed specifically for rocket engine main combustion chamber liners. In this research, the effect of Cr addition to GRCop-84 alloy is investigated to assess the composition-structure-property relationship. Near 100% dense samples were successfully deposited using laser metal deposition (LMD) with successive addition of Cr (0.5, 1.0, 1.5, 5, and 10 wt.%) to the GRCop-84. Microstructural investigation revealed the presence of Cr2Nb intermetallic, egg-shaped Cr particles, and Cu-Cr fiber-like eutectic phases with primary Cu matrix. Interestingly, the eutectic phase was primarily observed along the Cu cell boundaries. The length of the eutectic fibers grew from 0.3 to 1.7 μm, and the resulting hardness increased from 143 to 171 HV with the addition of Cr from 0.5 to 10 wt.%, respectively. These promising preliminary results show improvement in mechanical properties of GRCop-84 alloy with the addition of Cr and better overall performance.

4:35 PM  Cancelled
In Situ Investigation on the Multi-scale Deformation Mechanisms in Additively Manufactured Hierarchical Boron Nitride Nanotube Based Composites: Tyler Dolmetsch1; Tanaji Paul1; Cheng Zhang1; Benjamin Boesl1; Arvind Agarwal1; 1Florida International University
    In this study, hierarchical boron nitride nanotube (BNNT) reinforced composites were created using a layer-by-layer additive manufacturing approach that sandwiches aligned BNNT mats, fibers, and foams (high-volume of BNNTs) into BNNT reinforced resins (low-volume of BNNTs). In situ mechanical testing was performed inside a scanning electron microscope to provide real-time visualization of deformation and failure mechanisms such as nanotube pull-out and crack bridging at multiple scale lengths. The unique deformation mechanisms of high-volume fraction BNNT layers are investigated using in situ tension, compression, and indentation techniques. Localized indentation was used to probe the interfacial interactions and strength of these high-volume fraction layers with the surrounding polymer matrix. Cyclic loading and unloading were performed to study the fatigue, creep, and failure mechanisms of the composites under dynamic loading. Finally, in situ high-temperature indentations was conducted to gain a fundamental understanding of the elevated temperature mechanics of these hierarchical composites.