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GMAW and GTAW 3D printing microsctructure literature review

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This literature review supports the work of the Open-source metal 3-D printer.

Contents

GMAW[edit]

Most of the GMAW papers are papers focused on getting good 3-D print quality, but very few look at the effects of microstructure on print properties.

Heard, D. W., Brophy, S., & Brochu, M. (2012). Solid freeform fabrication of Al-Si components via the CSC-MIG process.' 'Canadian Metallurgical Quarterly',' '51'(3), 302–312.'[edit]

  • 4 layers of 4047 were GMAW 3-D printed onto 6061 coupons and an analogous Al alloy (Al-12%Si) was cast.
  • Properties and microstructures of the as-printed 4047 were compared with the as-cast material.
  • SDAS analysis of the 3-D printed layers showed a coarsening of the SDAS with increasing layer height. Authors attributed this to heat build-up in the 6061 print substrate and a subsequent reduction of cooling rate in the sample.
  • Faster cooling changed the eutectic structure to a more fibrous shape. Slower cooling created a eutectic structure that was more acicular.
  • The authors also compared microstructures in 3 layers of weld with and without a 5 minute cooling period between each layer. A 5 minute cooling period between layers produced a consistent SDAS size in subsequent printed layers (i.e. layer 1 SDAS = layer 2 SDAS).
  • Dendritic structures in the 1st print layer weren’t aligned  competitive growth of dendrites. Growth direction directly affected by direction of heat flux. Since the 1st layer is in direct contact with a substrate, there’s a two-dimensional heat flux and 2 different preferred growth orientations were observed via XRD: (111) and (200).
  • As more layers were printed, dendritic structures had a more aligned and consistent growth direction. Heat extraction mostly one-dimensional. Preferential solidification orientation was in the (200).
  • Hardness and flexural strength were characterized. Flexural strength of the 3-D printed material was statistically equivalent to the cast counterpart. Flexural strain of 3-D printed 4047 was less than that of the cast Al-12%Si.
  • Fracture surfaces of the 3-D printed and cast specimens were compared. Cast sample failed by brittle failure along the eutectic Si plates. The 3-D printed sample exhibited dimples (plastic deformation prior to failure) attributed to a change in morphology and a size reduction of the Si particles.

Meng, F. J., Ba, D. M., Yin, F. L., & Du, J. (2014). Microstructure Analysis on GMAW Additive Manufacturing Parts Constrained by Electromagnetism.' 'Advanced Materials Research',' '887-888', 1152–1155.[edit]

  • GMAW 3DP of H08Mn2Si steel onto hot rolled 45 steel metal.
  • Electromagnetic field was applied to reduce and improve microstructure – not described in detail though.
  • Microstructure in the middle of layers is fine equiaxed ferrite. At layer boundaries the microstructure transitions to coarse ferrite. Microstructure is coarser at layer boundaries because part of the previously printed layer is remelted.

Song, Y.-A., Park, S., Choi, D., & Jee, H. (2005). 3D welding and milling: Part I–a direct approach for freeform fabrication of metallic prototypes. 'International Journal of Machine Tools and Manufacture',' '45'(9), 1057–1062.[edit]

  • This paper mostly focuses on a description of their welding and milling system.
  • ER70S-6 steel wire was welded onto steel. Their print quality was atrocious (re: top of Figure 5) but milling after every layer significantly improved print quality.
  • Microstructure was finer where there was faster cooling (first printed layers). Microstructure was coarser where there was slower cooling (top layers). The samples were harder where there was a finer microstructure.
  • Table 1 includes a comparison of this 3D welding and milling density, accuracy, surface roughness, and mechanical strength with those of parts produced by other 3D printing processes.

Zhu, S., Li, C., Shen, C.-D., & Liu, J. (2010).'Microstructure and micro mechanical property of part formed by GMAW surfacing rapid prototyping' '(Vol. 419–420).[edit]

  • The abstract doesn’t mention control of the microstructure, but the microstructures of the steel 3-D printed parts were at least evaluated.
  • The authors made their own wire (could be useful for troubleshooting our wire making).

GTAW-Based 3-D Printing Microstructure-Related Papers[edit]

Baufeld, B., Brandl, E., & van der Biest, O. (2011). Wire based additive layer manufacturing: Comparison of microstructure and mechanical properties of Ti–6Al–4V components fabricated by laser-beam deposition and shaped metal deposition. Journal of Materials Processing Technology, 211(6), 1146–1158.[edit]

  • As-fabricated and heat treated specimens were analyzed, both for Laser beam weld 3DP and GTAW based 3DP.
  • This paper seems to mostly focus on microstructural characterization, small deviations to discuss fatigue testing and hardness results.
  • Both methods exhibited elongated grains, layered surfaces, and banded meso-structures.
  • Finer microstructures exhibited at the top layers. Coarser microstructures near specimen bottom.

Horii, T., Kirihara, S., & Miyamoto, Y. (2008). Freeform fabrication of Ti–Al alloys by 3D micro-welding. Intermetallics, 16(11–12), 1245–1249.[edit]

  • Micro-GTAW
  • Used several 200 µm Ti and Al wires and two separate wire feeders
  • Analyzed properties of 3 different ratios of Ti to Al wire additions; they also purposely made a sample with a compositional gradient
  • Some microstructural images and comparison to phase diagram. Worth looking at.

Horii, T., Ishikawa, M., Kirihara, S., Miyamoto, Y., & Yamanaka, N. (2007). Development of Freeform Fabrication of Metals by Three Diminsional Micro-Welding. Solid State Phenomena, 127, 189–194.[edit]

Horii, T., Kirihara, S., & Miyamoto, Y. (2009). Freeform fabrication of superalloy objects by 3D micro welding. Materials & Design, 30(4), 1093–1097.[edit]

  • Same system described in the 2008 Horii paper
  • Authors printed Inconel 600 alloy
  • Comparison of bead stability based on type of tungsten electrode, “slope up time”.
  • Microstructures given. The layers in Figure 7 look just like what we usually see in 3-D printed 4000 series Al.
  • Authors characterized mechanical properties

Jandric, Z., Labudovic, M., & Kovacevic, R. (2004). Effect of heat sink on microstructure of three-dimensional parts built by welding-based deposition. International Journal of Machine Tools and Manufacture, 44(7–8), 785–796.[edit]

  • AISI 1018 steel GTAW 3DP
  • Performed microstructural analysis on fusion and heat affected zones of the welds
  • This study seems very similar to the work our enterprise teams did this year. The authors of this study looked at the effect of apparent heat sink size on 3DP cooling and properties.
  • The fusion zone contained coarse columnar dendrites governed by constitutional super cooling
  • The top layer of all of the welds exhibited equiaxed dendrites but the underlying layer microstructures varied depending on the amount of heat extraction. The “best” microstructure achieved with samples with the most uniform heat transfer.
  • More acicular ferrite was formed in samples welded on a larger volume heat sink (i.e., more cooling)
  • Samples were harder in the top layer and softest in the first layer although this trend was slight.
  • Future work cited: In order to improve GTAW 3DP print quality, heat input into weld should be adjusted based upon volume of the heat sink so that the same max temp is applied to all layers.

Ma, Y., Cuiuri, D., Hoye, N., Li, H., & Pan, Z. (2015). The effect of location on the microstructure and mechanical properties of titanium aluminides produced by additive layer manufacturing using in-situ alloying and gas tungsten arc welding. Materials Science and Engineering: A, 631, 230–240.[edit]

  • Twin wire feeders to feed in ~1mm diameter wire
  • For printing with GTAW their print quality doesn’t look that much nicer than ours.
  • Microstructural characterization – layered structures like ours
  • Also performed EDS, harness measurements, and tensile properties
  • Comparisons of microstructure to Ti-Al phase diagram

Ma, Y., Cuiuri, D., Hoye, N., Li, H., & Pan, Z. (2014). Characterization of In-Situ Alloyed and Additively Manufactured Titanium Aluminides. Metallurgical and Materials Transactions B, 45(6), 2299–2303.[edit]

  • Seems like an introductory paper to their 2015 paper.

Terakubo, M., Oh, J., Kirihara, S., Miyamoto, Y., Matsuura, K., & Kudoh, M. (2005). Freeform fabrication of titanium metal by 3D micro welding.Materials Science and Engineering: A, 402(1–2), 84–91.[edit]

  • Ti printing via pulsed GTAW 3-D printing
  • Tested two different types of shield gas (Ar and Ar-4% Hydrogen)
  • PV study: Effects of arc current on bead height, contact angle, bead size
  • Some microstructures given
  • Performed Vickers hardness

Wang, H., Jiang, W., Ouyang, J., & Kovacevic, R. (2004). Rapid prototyping of 4043 Al-alloy parts by VP-GTAW. Journal of Materials Processing Technology, 148(1), 93–102.[edit]

  • Variable Polarity (VP) GTAW 3-D Printed 4043. 4043 was printed on 6061 aluminum plate. A 120-layer cylinder was printed. Each weld layer had a height of 0.2-0.45mm depending on printer & welder parameters.
  • Authors observed a layered microstructure (like my Mechanical Properties paper results) in which layers of coarse microstructure would yield to layers of fine microstructure.
  • Average SDAS in upper layers is approximately 4µm and approximately 8 µm in lower regions.
  • Fastest cooling was reported in the top layers.
  • Cooling rates in this type of 3DP are faster than those reported for traditional fusion welding (no specific numbers given).

Not sure if GMAW or GTAW[edit]

Li, C., Zhu, S., Shen, C.-D., & Liu, J. (2010). Microstructure and micro mechanical properties of mild-steel parts fabricated by surfacing rapid forming. Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment, 31(4), 45–49.[edit]

  • They manufactured their own metal cored wires.
  • Layered characteristics observed in the microstructure. Pearlite decreases and ferrite (I’m assuming acicular ferrite) increases at higher layers as opposed to initially printed layers.