Additive Manufacturing of Metals: Microstructure, Properties and Alloy Development: Al-based Alloys
Program Organizers: Prashanth Konda Gokuldoss, Tallinn University of Technology; Juergen Eckert, Erich Schmid Institute of Materials Science; Zhi Wang, South China University of Technology
Monday 8:00 AM
October 18, 2021
Room: A115
Location: Greater Columbus Convention Center
Session Chair: Jovid Rakhmonov, Northwestern University
8:00 AM
Additively Manufactured ALSi10Mg Thin Fins via Laser Powder Bed Fusion: A Parametric Analysis: Adnen Mezghani1; Abdalla Nassar2; Timothy Simpson1; 1Pennsylvania State University; 2Applied Research Laboratory
Laser Powder Bed Fusion (LPBF) Additive manufacturing (AM) of heat exchangers (HEX), compared to traditional manufacturing methods, offers greater design freedom and potential for light-weighting, and topology optimization. AM thus enables considerable increase in performance. However, process limitations and build defects (e.g., minimum feature size limits and unwanted porosity) are serious obstacles facing the advancement of AM of HEX devices. In this study, single-scan and double-scan fins were fabricated to investigate the effects of rescanning strategy, inclination angle, laser power, and laser scan speed on the thickness, porosity, and surface roughness of thin fins fabricated in the aluminum alloy AlSi10Mg. A processing map is developed, allowing for the prediction and control of fin thickness and porosity, given a fin inclination angle. An anticipated future outcome of this work is the development of a process framework for LPBFAM of heat exchangers.
8:20 AM
Effect of Direct Metal Laser Sintering Build Parameters on Defects and Ultrasonic Fatigue Performance of Additively Manufactured AlSi10Mg: Robert Rhein1; Qianying Shi2; Srinivasan Arjun Tekalur1; J Wayne Jones2; Jason Carroll1; 1Eaton Corporation; 2University of Michigan
The high cycle fatigue behavior of additively manufactured AlSi10Mg is evaluated using ultrasonic fatigue as a means to accelerate fatigue testing. Build parameters during the additive manufacturing process are varied, and their effect on defect type, size, and distribution is determined. These defects in turn are found to influence fatigue behavior, which is analyzed using the Murakami model. The ultrasonic fatigue test results are interpreted in the context of applied stress intensity factor and an optimized fatigue limit fit. Two different kinds of physical behavior, representing Murakami dependence and a long crack regime are found to best correlate the fatigue life behavior. This information can be used to tailor defect size, type, and distribution to obtain necessary high cycle fatigue properties.
8:40 AM
Effects of Process Parameters, Post-processing, and Defects on Tension and Fatigue Properties of LPBF AlSi10Mg: Austin Ngo1; Collin Sharpe1; Varthula Jayasekera2; Brett Conner2; Holly Martin2; Christopher Tuma1; John Lewandowski1; 1Case Western Reserve University; 2Youngstown State University
Mechanical testing specimens of AlSi10Mg were fabricated via LPBF. Specimens were built in XY and Z orientations using multiple parameter sets, including optimized parameter sets to establish the baseline material properties and sub-optimal parameter sets to systematically induce lack of fusion defects of varying sizes. Multiple types of post-processing heat treatments were applied to the baseline and defect-induced specimens to study the effects of T6 heat treatment and/or HIP on defect population and mechanical properties. Specimens were machined for tension testing, constant amplitude fatigue testing, and three-point bend fatigue crack growth testing. Defect characteristics collected by metallography and fractography are compared across build parameter sets. Crack front plastic zone size is calculated and discussed in terms of interactions with defects and microstructure. The effects of build parameters, build orientation, post-processing, and lack of fusion defects on the subsequent mechanical properties will be covered.
9:00 AM
Effects of Process Parameters and Defects on S-N Fatigue of LPBF AlSi10Mg: Collin Sharpe1; Austin Ngo1; Christopher Tuma1; Michael Shinohara1; Holly Martin2; John Lewandowski1; 1Case Western Reserve University; 2Youngstown State University
The effects of changes in process parameters and resulting defects on tension and S-N fatigue behavior of additively manufactured AlSi10Mg have been determined through fatigue testing of cylindrical samples according to ASTM E466. Samples were prepared under the following conditions: nominal + HIP (A), large defects + HIP (B), small to medium defects + HIP (G), many defects + HIP (D), large defects with no HIP (E), and small to medium defects with no HIP (F). Optical and SEM images of the fracture surfaces have been captured and used to quantify fatigue-initiating defects, including those that did not produce catastrophe. Differences in the characteristics and number of defects that initiated fatigue cracking will be reviewed in conjunction with the tension and S-N data.
9:20 AM
Process Optimization and Microstructural Analysis for Laser Powder Bed Fusion of AlMgZr Alloy: Nellie Pestian1; Thomas Carmody1; Dan Satko1; Evan Diewald2; Christian Gobert2; Anthony Rollett2; Jack Beuth2; Ayman Salem1; Nam Phan3; Jan Kasprzak3; 1MRL Materials Resources LLC; 2Carnegie Mellon University; 3Naval Air Systems Command
The utilization of additively-manufactured (AM) aluminum parts for aerospace applications requires the avoidance of hot tearing cracks that plague the AM of conventional alloys (e.g. Al 6xxx and 7xxx series). While various nucleates have been demonstrated to enable crack-free AM of high-strength Al alloys, Zr-based alloys are capturing a lot of attention due to lower cost. In this presentation, we introduce a laser powder bed fusion (LPBF) process map for a novel AlMgZr alloy. This multi-dimensional process map includes the effect of laser power, scan speed, hatch spacing, and spot size. A model-based design of experiments was used to predict the volume of the melt pool using analytical and numerical predictions based on a volumetric heat source model. Microstructure and defect evolution were captured in cuboid coupon samples using conventional metallography and microCT. A process window for minimum defects is presented with a path for ICME-based scaling to part level.
9:40 AM
Characterization of Near-eutectic Al-Ce with Sc and Zr Microadditions Processed by Rapid Laser Remelting: Jovid Rakhmonov1; Clement Ekaputra1; David Weiss2; David Dunand1; 1Northwestern University; 2Eck Industries, Inc.
The creep resistance of additively-manufactured near-eutectic Al-Ce alloys can be substantially improved by microadditions of Sc and Zr to form thermally-stable, L12-type nanoprecipitates in the α-Al phase upon subsequent aging. In this study, an Al-Ce-Sc-Zr alloy is first produced by conventional casting, then subjected to laser remelting to mimic the high cooling rates offered by powder-bed laser fusion. The as-cast and laser-remelted alloys are then aged to induce the precipitation of L12-type Al3(Sc,Zr) nanoprecipitates. Microstructure and property evolutions following laser remelting and subsequent aging are investigated using SEM, TEM and hardness testing. The results are compared with those of the cast alloy subjected to the same aging heat treatment. Significant improvements in hardness upon aging of the laser-remelted alloy are explained by the combination of a fine eutectic microstructure and high number density of L12-type nanoprecipitates.