Additive Manufacturing of Functional, Energy, and Magnetic Materials: Additive Manufacturing of NiTi
Sponsored by: TMS Functional Materials Division, TMS: Additive Manufacturing Committee, TMS: Magnetic Materials Committee
Program Organizers: Markus Chmielus, University of Pittsburgh; Sneha Prabha Narra, Carnegie Mellon University; Mohammad Elahinia, University of Toledo; Reginald Hamilton, Pennsylvania State University; Iver Anderson, Iowa State University Ames Laboratory
Thursday 8:30 AM
March 18, 2021
Room: RM 2
Location: TMS2021 Virtual
8:30 AM
Composition Control in Laser Powder Bed Fusion Additive Manufacturing Through Differential Evaporation: Meelad Ranaiefar1; Ibrahim Karaman1; Alaa Elwany1; Raymundo Arroyave1; 1Texas A&M University
Differential evaporation during part fabrication using laser powder bed fusion additive manufacturing can contribute to variation in composition. This uncontrolled evaporation is a prevalent issue throughout the additive manufacturing process and is associated with uncontrolled changes in structure and properties, along with reduced performance of a part. However, we can utilize the underlying mechanisms of differential evaporation to direct processing parameters, control composition, tailor location specific properties, and achieve desired performance. In this work, a model for predicting differential evaporation and the associated change in composition during laser powder bed additive manufacturing is presented. This is used to investigate the effects of alloying elements and processing parameters on evaporation and composition.
8:50 AM
Toward Understanding the Effect of Selective Laser Re-melting on the Mechanical Properties of the SLM Fabricated Nitinol: Parisa Bayati1; Keyvan Safaei1; Mohammadreza Nematollahi1; Ahmadreza Jahadakbar2; Mohammad Mahtabi3; Mohammad Elahinia1; 1The University of Toledo; 2Thermomorph LLC; 3The University of Tennessee at Chattanooga
Although additive manufactured (AM) Nitinol parts exhibits acceptable shape memory and superelasticity in compression loadings, they provide a relatively weak tensile and fatigue properties in comparison to the conventionally manufactured Nitinol. As a solution to improve the mechanical properties of the AM fabricated Nitinol and to reduce the internal microvoids, we have investigated the effect of re-melting during the SLM procedure after fabricating each layer. A series of re-melting process parameters including different scanning speed and laser powers were studied through mechanical testing, DSC, and SEM analysis. We have shown that proper selection of the re-melting process parameters improves the powder bed quality of eachlayer, increases the density of the fabricated parts by up to %1.5, and reduces the top surface roughness by up to %50. Improving the density and reducing the internal voids may improve the mechanical properties, and it is also being investigated in this work.
9:10 AM
Selective Laser Melting of Defect-free NiTi SMA Parts Using a Process Optimization Framework: Lei Xue1; Chen Zhang1; Kadri Atli1; Bing Zhang1; Alaa Elwany1; Raymundo Arroyave1; Ibrahim Karaman1; 1TAMU
This study reports fully dense Nickel-titanium (NiTi) parts fabricated using laser powder bed fusion (L-PBF) and showed good ductility up to 16%, shape memory effect and partial superelasticity. The desired range of processing parameters was determined for two compositions NiTi powder guided by a framework based on single tracks experiments and an analytical model to predict the melt pool dimensions accurately. The defect free samples were fabricated and tested by following the framework. Functional properties of NiTi are highly sensitive to the composition hence the process parameters. The flexibility of parameter selection and potential composition control by elemental evaporation showed by this work may open the possibility to fabricate functional NiTi parts or device without post-processing.