Additive Manufacturing: Processing Effects on Microstructure and Material Performance: Process Variables II
Sponsored by: TMS: Additive Manufacturing Committee
Program Organizers: Eric Lass, University of Tennessee-Knoxville; Joy Gockel, Wright State University; Emma White, DECHEMA Forschungsinstitut; Richard Fonda, Naval Research Laboratory; Monnamme Tlotleng, University of Johannesburg; Jayme Keist, Pennsylvania State University; Hang Yu, Virginia Polytechnic Institute And State University
Wednesday 8:30 AM
February 26, 2020
Room: 6E
Location: San Diego Convention Ctr
Session Chair: Joy Gockel, Wright State University
8:30 AM
Additive Manufacturing of Crack-prone Materials: A Process-and material-based Approach to Parameter Development: Austin Dicus1; 1Carpenter Technology
As additive manufacturing (AM) continues to find applications in aerospace, power generation, oil/gas, and medical markets, there is a desire to identify AM parameter sets for crack-prone alloys. These materials are difficult to weld because they are susceptible to hot cracking, strain-age cracking and thermal stresses. In laser powder bed fusion (LPBF) processes, conventional energy density equations consider process parameters but ignore machine and material properties. Carpenter Technology has developed a new approach that integrates process, machine and materials parameters, and leads to the suppression of porosity and cracking. Usage of this approach aides in the development of parameter sets for existing alloys and accelerates the design of new alloys specifically tailored to LPBF AM. Examples of crack-free AM Hastelloy® and Custom 465® are reviewed. Microstructures in as-built and as-aged conditions along with performance of a high-γ’ Ni-base and a Co-Ni superalloy specifically optimized for AM are also discussed.
8:50 AM
Eliminating Micro-cracking in Inconel 713ELC Fabricated by a Powder-bed-fusion Additive Manufacturing with Electron Beam: Yuchao Lei1; Kenta Aoyagi1; Dong-Soo Kang2; Kosuke Kuwabara2; Kinya Aota2; Akihiko Chiba1; 1Institute for Materials Research, Tohoku University; 2Global Research & Innovative Technology Center (GRIT), Hitachi Metals, Ltd.
Inconel 713ELC (IN713-ELC) is one of γ’ precipitate strengthened superalloy, which exhibits excellent resistance to mechanical degradation at a temperature range of 650 ~ 980 °C. IN713-ELC is usually manufactured by casting due to its poor hot workability. Recently, producing IN713-ELC parts by electron beam melting (EBM), one of the additive manufacturing technologies, has been of attractiveness in the industry because EBM can provide near-net shape metal parts. In this study, through an efficient method for optimizing process parameters based on support vector machine (SVM) [1], samples with superior mechanical properties have been manufactured. Moreover, parameters leading to crack-free samples were successfully extracted from SVM predicted process map. Finally, the cracking mechanism was discussed based on the comprehensive study by comparing the cracked sample, crack-free sample, and Inconel 718 with small cracking susceptibility. [1] K. Aoyagi, et al., Additive Manufacturing, 27 (2019) 353-362.
9:10 AM
Selective Laser Melting Fabrication of Ultra-high Strength Martensitic Steel: Raiyan Seede1; David Shoukr1; Bing Zhang1; Austin Whitt1; Sean Gibbons2; Philip Flater2; Alaa Elwany1; Raymundo Arroyave1; Ibrahim Karaman1; 1Texas A&M University; 2Air Force Research Laboratory
Ultra-high strength steels (UHSSs) have attracted increasing interest for their use in the automotive and aerospace industries and in defense applications due to their high yield strengths and reasonable ductility. The Air Force Research Laboratory recently developed a relatively inexpensive UHSS called AF9628. This martensitic steel can exhibit strengths greater than 2 GPa with more than 10% elongation with proper microstructural refinement, in particular via refinement in prior austenite grain size. In an effort to produce high strength parts with a high degree of control over geometry, this work studies the effect of selective laser melting (SLM) process parameters on the mechanical properties of AF9628. Fully dense samples were achieved over a range of process parameters. Ultimate tensile strengths of up to 1.43 GPa and elongations of up to 12.3% were observed in as-printed specimens. Variation in process parameters did not significantly affect the mechanical response under compression.
9:30 AM
Surface Roughness of Hastelloy-X Components Manufactured by Selective Laser Melting: Yang Tian1; Dacian Tomus1; Aijun Huang1; Xinhua Wu1; 1Monash University
Poor surface quality presents a major limitation to the widespread use of selective laser melting (SLM) technology. In this study, systematic research has been carried out to study the influences of different processing parameters and scanning strategies on surface roughness of SLMed Hastelloy X using EOSM280 machine. Processing window is proposed which would provide support to identify appropriate processing conditions and meet specific demand. An optimum condition for achieving the lowest roughness for up-skin and down-skin surface has been obtained respectively. Surface characterizations revealed that melt pool shape and the presence of partially melted particles are vital factors in determining the surface profile and resultant roughness in the final parts. Computer simulation was also used to investigate the heat conduction through powder and solid and their contributions to the roughness on these two types of surfaces. The simulated result has been found to be consistent with the measured.
9:50 AM
Gas Atomization and Powder Bed Fusion Optimization Studies for the Al10SiMg Alloy: Sharon Park1; George Benson1; Thinh Huynh1; Holden Hyer1; Le Zhou1; Edward Dein1; Yongho Sohn1; 1University of Central Florida
perimental investigations were carried out to optimize gas atomization and laser powder bed fusion (PBF) for Al10SiMg alloy. Atomization parameters, such as gas pressure, melt temperature and melt flow rate were correlated to the powder yield, particle size distribution and microstructure with due respect to particle size distribution suitable for PBF. Powder bed fusion parameters such as laser power, scan speed, hatch spacing and slice thickness were independently varied to examine the influence of particle size distribution and powder recycling on the density, microstructure and mechanical behavior of as-built Al10SiMg alloy. Excellent “printability,” well-documented for Al10SiMg alloy was observed for a wide range of laser PBF parameters, particle size distribution, and powder recycling. Defects arising from insufficient melting or evaporation/boiling associated with particle size distribution and continued powder reuse provided some insight to the absorption-melting-solidification characteristics of Al10SiMg alloy during PBF.
10:10 AM Break
10:30 AM
Towards an Integrated Experimental and Computational Framework for Large-scale Metal Additive Manufacturing: Xiaohua Hu1; Andrzej Nycz1; Yousub Lee1; Benjamin Shassere1; Srdjan Simunovic1; Mark Noakes1; Yang Ren2; Xin Sun1; 1Oak Ridge National Laboratory; 2Argonne National Laboratory
Using the Metal Big Area Additive Manufacturing (MBAAM) system, a thin steel wall was manufactured from a low carbon steel wire. The wall was then characterized comprehensively by high-throughput high-energy X-ray diffraction (HEXRD), electron backscatter diffraction (EBSD), and in-situ HEXRD tensile tests. With the predicted temperature histories from the finite element-based additive manufacturing process simulations, the correlations between processing parameters, microstructure, and properties were established. The correlation between the final microstructure with the predicted temperature history is well explained with the material's continuous cooling transformation (CCT) diagram calculated based on the composition of the low carbon steel wire. The measured mechanical strength is then related to the microstructural feature size (grain or lath size) observed in those locations. A good correlation is found between the mechanical properties, microstructure features and the temperature history at various locations of the printed wall.
10:50 AM
The Effects of Alloy Composition on Microstructure and Mechanical Properties of Duplex Stainless Steel Produced by Additive Manufacturing: Andrew Iams1; Todd Palmer1; 1Pennsylvania State University
While additive manufacturing shows great promise for production of complex part geometries and for repair applications of many alloy systems, the additive manufacturing of duplex stainless steel alloys have been limited by the inability to maintain a balanced ferrite/austenite microstructure in the as-deposited condition. In order to investigate the impact of the complex thermal histories inherent to the additive manufacturing process on the microstructure and mechanical properties, a laser-based directed energy deposition process was used to fabricate lean (UNS S32101), standard (UNS S32205), and super (UNS S32507) duplex structures. The effects of post-process hot isostatic pressing on duplex stainless steel microstructures and properties are also investigated.
11:10 AM
3D Characterization of Alpha Phase Morphology and Variant Selection in EBM Ti-6Al-4V: Ryan DeMott1; Phillip Stephenson1; Peter Collins2; Nima Haghdadi1; Xiaozhou Liao3; Simon Ringer3; Sophie Primig1; 1UNSW Sydney; 2Iowa State University; 3University of Sydney
The microstructure of Ti-6Al-4V is in large part determined by alpha variant selection during the beta-to-alpha transformation. This can result in complex microstructures and significantly impact mechanical properties through the formation of macro-textured regions. The extreme thermal gradients and cyclic thermal loading in additive manufacturing processes can lead to variations in the alpha variant selection behavior and final morphology.In this work, Ti-6Al-4V blocks were built using electron beam melting (EBM) with three different scan strategies: linear, random, and Dehoff, in order to generate different thermal histories. The microstructures were characterized using 2D and 3D EBSD and variations in alpha lath morphology, alpha variant selection, and prior and retained beta textures were observed across the three different builds. Examining these complex microstructures in 3D allows new insights into beta to alpha phase transformation and the competing mechanisms of alpha variant selection.
11:30 AM
Study the Effect of Thermal Signatures on Microstructural Variation of EBM Additively Manufactured Ti-6Al-4V Builds: Meiyue Shao1; Chris Blackwell1; Sriram Vijayan1; Sabina Kumar2; Sudarsanam Babu2; Joerg Jinschek1; 1The Ohio State University; 2University of Tennessee
In the electron beam melting - additive manufacturing (EBM-AM) process, materials experience complex thermal signatures affecting microstructure and, ultimately, the mechanical properties of the final AM build. Here, we investigate the variability in microstructure of EBM-AM Ti-6Al-4V (Ti64) blocks, built with different beam fill strategies. To achieve statistically significance in our characterization approach and be able to correlate the results with subsequent mechanical property measurements, we quantify the complex variations in microstructural features, such as alpha lath thickness, beta phase width and phase fraction, at well-chosen locations throughout the AM build. SEM and EBSD images as well as EDS maps were acquired. The quantification of microstructural features has been automated using specific MIPAR software recipes. EDS maps provide correlative information about local chemical composition variations. These results, obtained from EBM-AM Ti64 blocks, are correlated to the thermal signatures used in the EBM process with varying beam fill strategies.
11:50 AM Cancelled
The Microstructures and Mechanical Properties at Different Forming Positions of A Box-shaped Ti-6Al-4V Alloy Part Fabricated by Selective Laser Melting: Jingbo Gao1; Deliang Zhang*1; 1Northeastern University
A box-shaped Ti-6Al-4V (wt.%) alloy part was fabricated by selective laser melting (SLM) with gas atomized powder and annealed at 800℃ for 2 h. The microstructures and mechanical properties at various positions of the part were studied. The microstructures at all positions consisted of α lamellae with lengths of 50-100 μm and widths of 0.2-2 μm. {101 ̅2} and {112 ̅0} texture was observed. The α lamellae in the top area far away from the substrate were finer than those in the bottom area, and the former exhibited a better combination of yield strength (965 MPa), ultimate tensile strength (1043 MPa) and elongation to fracture (11.1%) than the latter (961 MPa, 1042 MPa and 8.1%). The microstructures and mechanical properties did not vary much with the horizontal distances from the centerline.