Jorge Mireles

Development of a Fused Deposition Modeling System for Low Melting Temperature Metal Alloys

This research focused on extending the applications of fused deposition modeling (FDM) by extrusion and deposition of low melting temperature metal alloys to create three-dimensional metal structures and single-layer contacts which may prove useful for electronic interconnects. Six commercially available low melting temperature solder alloys (Bi36Pb32Sn31Ag1, Bi58Sn42, Sn63Pb37, Sn50Pb50, Sn60Bi40, Sn96.5Ag3.5) were tested for the creation of a fused deposition modeling for metals (FDMm) system with special attention given to Sn–Bi solders. An existing FDM 3000 was used and two alloys were successfully extruded through the systems extrusion head. Deposition was achieved through specific modifications to system toolpath commands and a comparison of solders with eutectic and non-eutectic compositions is discussed. The modifications demonstrate the ability to extrude simple single-layer solder lines with varying thicknesses, including sharp 90 deg angles and smooth curved lines and showing the possibility of using this system for printed circuit board applications in which various connections need to be processed. Deposition parameters altered for extrusion and the deposition results of low melting temperature metal alloys are introduced.

Analysis and correction of defects within parts fabricated using powder bed fusion technology

Quality assurance is an important topic for additive manufacturing (AM) and often seen as a requirement for the transition and adoption of the technology toward fabrication of end use applications. As AM technologies are used for production, it is necessary to ensure high quality, repeatable, and reproducible components are manufactured. Various nondestructive examination techniques have been used to evaluate AM-fabricated parts to determine part quality post-fabrication (e.g. scanning and/or microstructural characterization). In situ monitoring methods have been developed for AM technologies to enable defect detection and have potential to be used for in situ monitoring and correction of fabrication anomalies (e.g. undesired temperature gradients and porosity). In this research, defects (e.g. pores) were seeded into parts fabricated using the powder bed fusion AM process, electron beam melting, and monitored using in situ infrared (IR) thermography. Results from layerwise thermography were compared with results obtained using computer tomography (CT) scanning techniques. Although the measured geometry of the seeded defects between IR thermography and CT was substantially different (area difference of ~60%), the thermographs did provide a good indication of defects present within a fabricated part. Furthermore, defect correction methods were evaluated including post-processing methods such as hot isostatic pressing as well as in situ correction methods such as layer re-melting. Re-melting a porous layer successfully corrected defects and demonstrates a potential method for in situ defect correction if implemented in future systems equipped with automatic feedback control of powder bed fusion processes.

Enhancement of Low-Cycle Fatigue Performance From Tailored Microstructures Enabled by Electron Beam Melting Additive Manufacturing Technology

Electron beam melting (EBM) additive manufacturing (AM) technology has allowed the layerwise fabrication of parts from metal powder precursor materials that are selectively melted using an electron beam. An advantage of EBM technology over conventional manufacturing processes has been the capability to change processing variables (e.g., beam current, beam speed, and beam focus) throughout part fabrication, enabling the processing of a wide variety of materials. In this research, additional scans were implemented in an attempt to promote grain coarsening through the added thermal energy. It is hypothesized that the additional energy caused coarsening of Ti-6Al-4V microstructure that has been shown to increase mechanical properties of as-fabricated parts as well as improve surface characteristics (e.g., reduced porosity). Fatigue testing was performed on an L-bracket using a loading configuration designed to cause failure at the corner (i.e., intersection of the two members) of the bracket. Results showed 22% fatigue life improvement from L-brackets with as-fabricated conditions to L-brackets with a graded microstructure resulting from the selective addition of thermal energy in the expected failure region. Three L-brackets were fabricated and exposed to a triple melt cycle (compared to the standard single melt cycle) during fabrication, machined to specific dimensions, and tested. Results for fatigue performance were within ∼1% of wrought L-brackets. The work from this research shows that new design procedures can be implemented for AM technologies that involve evaluation of stress concentration sites using finite element analysis and implementation of scanning strategies during fabrication that help improve performance by spatially adjusting thermal energy at potential failure sites or high stress regions.

High-kinetic inductance additive manufactured superconducting microwave cavity

Investigations into the microwave surface impedance of superconducting resonators have led to the development of single photon counters that rely on kinetic inductance for their operation, while concurrent progress in additive manufacturing, “3D printing,” opens up a previously inaccessible design space for waveguide resonators. In this manuscript, we present results from the synthesis of these two technologies in a titanium, aluminum, vanadium (Ti-6Al-4V) superconducting radio frequency resonator which exploits a design unattainable through conventional fabrication means. We find that Ti-6Al-4V has two distinct superconducting transition temperatures observable in heat capacity measurements. The higher transition temperature is in agreement with DC resistance measurements, while the lower transition temperature, not previously known in the literature, is consistent with the observed temperature dependence of the superconducting microwave surface impedance. From the surface reactance, we extract a London ...

Optical fabrication of lightweighted 3D printed mirrors

Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM) 3D printing technologies were utilized to create lightweight, optical grade mirrors out of AlSi10Mg aluminum and Ti6Al4V titanium alloys at the University of Arizona in Tucson. The mirror prototypes were polished to meet the λ/20 RMS and λ/4 P-V surface figure requirements. The intent of this project was to design topologically optimized mirrors that had a high specific stiffness and low surface displacement. Two models were designed using Altair Inspire software, and the mirrors had to endure the polishing process with the necessary stiffness to eliminate print-through. Mitigating porosity of the 3D printed mirror blanks was a challenge in the face of reconciling new printing technologies with traditional optical polishing methods. The prototypes underwent Hot Isostatic Press (HIP) and heat treatment to improve density, eliminate porosity, and relieve internal stresses. Metal 3D printing allows for nearly unlimited topological constraints on design and virtually eliminates the need for a machine shop when creating an optical quality mirror. This research can lead to an increase in mirror mounting support complexity in the manufacturing of lightweight mirrors and improve overall process efficiency. The project aspired to have many future applications of light weighted 3D printed mirrors, such as spaceflight. This paper covers the design/fab/polish/test of 3D printed mirrors, thermal/structural finite element analysis, and results.

Mechanical Behavior of Differently Oriented Electron Beam Melting Ti–6Al–4V Components Using Digital Image Correlation

Mechanical properties of additive manufactured metal components can be affected by the orientation of the layer deposition. In this investigation, Ti–6Al–4V cylindrical specimens were fabricated by electron beam melting (EBM) at four different build angles (0 deg, 30 deg, 60 deg, and 90 deg) and tested as per ASTM E8 Standard Test Methods for Tension Testing of Metallic Materials. With the layer-by-layer fabrication suggesting granting anisotropic properties to the builds, strain fields were recorded by digital image correlation (DIC) in the search for shear effects under uniaxial loads. For the validation of this measuring method, axial strains were measured with a clip extensometer and a virtual extensometer, simultaneously. Failure analysis of the specimens at different orientations was conducted to evidence the recording of shear strain fields. The failure analysis included fractography, optical micrographs of the microstructure distribution, and failure profiles displaying different failure features associated with the layering orientation. Additionally, an experimental study case of how the failure mode of components can potentially be designed from the fabrication process is presented. At the end, remarks about the shear effects found, and an insight of the possibility of designing components by failure for safer structures are discussed. [DOI: 10.1115/1.4040553]