Using Nanofibers to Make Ultra Fine Grained 7075 Aluminum
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Using Nanofibers to Make Ultra Fine Grained 7075 Aluminum Patrick McManus Department of Chemistry, University of Wisconsin Oshkosh, Oshkosh, WI 54901 Abstract The demand for stronger and lighter materials in aerospace has driven material science to develop numerous discoveries over the past century. Since the beginning of metallurgy, heat treating metal has been used to reduce the grain size of the material in order to increase its strength. My research has been centered around the idea that the ability to control nanofibers diameter and orientation make them an ideal candidate to engineer the grain size and orientation in a stamp forging process. By electrospinning 7075 aluminum alloy into nanofibers and heat treating the fibers to form a hybrid nanoparticle fiber form, the grain size can be dramatically reduced from (figure 1) the m to the nm scale (figure 2). Figure 2: ZnO nanofibers heat at 600 ℃ for 12 hours forming a hybrid nanoparticle fiber. Discussion The idea of forming ultra fine grained Al7075 is based on my ongoing research into ZnO nanofibers which formed a unique structure when heated to 600 ℃ (Figure 2). The addition of these structures significantly increased the surface area of the fibers which are typically smooth. This has led to my conclusion that if this nanofiber structure can be replicated in Al7075, they can be stamp forged to bring the crystals into cohesion, forming a significantly stronger form of the metal with significantly smaller grains forming interlocking nanostructures. This will in theory not only increase the dispersion of forces between grains but also along the fiber lattice, reinforcing the grain to grain bonds. Stamp forging will also eliminate deviations in structures like grain flow ( figure 3). Grain flow is a product of casting molten metal and can lead to the propagation of cracks and intergranular corrosion once they are formed. Current methods of producing UFG aluminum typically use cryogenic freezing. This process, while simpler, will not create grain sizes as small or have interwoven grain latices like that made from nanofibers. Procedure This research is still in development and formulation has been the primary results so far. Any future methods or formulation may be subject to significant deviation from what is listed here.The metal salts were first combined to make the 7075 alloy, combining by weight 76 parts aluminum acetate, 5 parts zinc acetate, 1 part copper acetate, and 2 parts magnesium acetate. The metal salt combination was then mixed in a 1:4 ratio with water. A separate polymer solution was then made by mixing a 1:5 ratio of PVP and ethanol. The metal solution was then combined under high mixing with the PVP solution at a 1: 2.2 ratio. To this was added 1% by weight DTAB to act as a surfactant and the sol-gel was left to mix under high stirring at STP for 24 hrs. The electrospinning process was performed using an 18 ga needle extruding 3.4 L/min of sol-gel at a distance of 20 cm from the collection plate. The applied voltage was set to 20 kV and the fibers were collected over a period of 46 hrs. The next steps to producing the nanofibers will be heating them in a furnace under an inert atmosphere to remove the polymer and prevent atmospheric oxidation of the Al7075 as it forms. SEM, XRD, and BET will be used to analyse the samples final results. Figure 1 : a. Grain structure of Al7075 (S., Sivasankaran & Ramkumar, Et al. 2019) Figure 3 : Grain flow of a traditionally forged and machined component. (J. Walters, C. Van Tyne, 2014) Conclusion While this research is still in the formulation phase of development, the concept shows promise for developing a new form of a widely used material. While the scaling up of electrospinning nanofiber technology is the main constraint for mass production of this material, the potential benefits make ultra fine grained Al7075 a practical choice for specialized parts in aerospace. References 1. S., Sivasankaran & Ramkumar, K R & Al-Mufadi, Fahad & Irfan, Osama. (2019). Effect of TiB2/Gr Hybrid Reinforcements in Al 7075 Matrix on Sliding Wear Behavior Analyzed by Response Surface Methodology. Metals and Materials International. 10.1007/s12540-019-00543-5 2. J. Walters, C. Van Tyne, Grain Flow in Forgings. Forge, Oct. 6, 2014 https://www.forgemag.com/articles/84265-grain-flow-in-forgings---the-basics
Transcript of Using Nanofibers to Make Ultra Fine Grained 7075 Aluminum
Using Nanofibers to Make Ultra Fine Grained 7075 AluminumPatrick McManus
Department of Chemistry, University of Wisconsin Oshkosh, Oshkosh, WI 54901Abstract
The demand for stronger and lighter materials in aerospace has driven material science to develop numerous discoveries over the past century. Since the beginning of metallurgy, heat treating metal has been used to reduce the grain size of the material in order to increase its strength. My research has been centered around the idea that the ability to control nanofibers diameter and orientation make them an ideal candidate to engineer the grain size and orientation in a stamp forging process. By electrospinning 7075 aluminum alloy into nanofibers and heat treating the fibers to form a hybrid nanoparticle fiber form, the grain size can be dramatically reduced from (figure 1) the 𝝁m to the nm scale (figure 2).
Figure 2: ZnO nanofibers heat at 600 ℃ for 12 hours forming a hybrid nanoparticle fiber.
DiscussionThe idea of forming ultra fine grained Al7075 is based
on my ongoing research into ZnO nanofibers which formed a unique structure when heated to 600 ℃ (Figure 2). The addition of these structures significantly increased the surface area of the fibers which are typically smooth. This has led to my conclusion that if this nanofiber structure can be replicated in Al7075, they can be stamp forged to bring the crystals into cohesion, forming a significantly stronger form of the metal with significantly smaller grains forming interlocking nanostructures. This will in theory not only increase the dispersion of forces between grains but also along the fiber lattice, reinforcing the grain to grain bonds. Stamp forging will also eliminate deviations in structures like grain flow ( figure 3). Grain flow is a product of casting molten metal and can lead to the propagation of cracks and intergranular corrosion once they are formed. Current methods of producing UFG aluminum typically use cryogenic freezing. This process, while simpler, will not create grain sizes as small or have interwoven grain latices like that made from nanofibers.
ProcedureThis research is still in development and formulation has been the primary results
so far. Any future methods or formulation may be subject to significant deviation from what is listed here.The metal salts were first combined to make the 7075 alloy, combining by weight 76 parts aluminum acetate, 5 parts zinc acetate, 1 part copper acetate, and 2 parts magnesium acetate. The metal salt combination was then mixed in a 1:4 ratio with water. A separate polymer solution was then made by mixing a 1:5 ratio of PVP and ethanol. The metal solution was then combined under high mixing with the PVP solution at a 1: 2.2 ratio. To this was added 1% by weight DTAB to act as a surfactant and the sol-gel was left to mix under high stirring at STP for 24 hrs. The electrospinning process was performed using an 18 ga needle extruding 3.4 𝝁L/min of sol-gel at a distance of 20 cm from the collection plate. The applied voltage was set to 20 kV and the fibers were collected over a period of 46 hrs. The next steps to producing the nanofibers will be heating them in a furnace under an inert atmosphere to remove the polymer and prevent atmospheric oxidation of the Al7075 as it forms. SEM, XRD, and BET will be used to analyse the samples final results.
Figure 1 : a. Grain structure of Al7075 (S., Sivasankaran & Ramkumar, Et al. 2019)
Figure 3 : Grain flow of a traditionally forged and machined component. (J. Walters, C. Van Tyne, 2014)
ConclusionWhile this research is still in the formulation phase of
development, the concept shows promise for developing a new form of a widely used material. While the scaling up of electrospinning nanofiber technology is the main constraint for mass production of this material, the potential benefits make ultra fine grained Al7075 a practical choice for specialized parts in aerospace.
References1. S., Sivasankaran & Ramkumar, K R & Al-Mufadi, Fahad & Irfan, Osama. (2019). Effect of TiB2/Gr Hybrid Reinforcements in Al 7075 Matrix on
Sliding Wear Behavior Analyzed by Response Surface Methodology. Metals and Materials International. 10.1007/s12540-019-00543-52. J. Walters, C. Van Tyne, Grain Flow in Forgings. Forge, Oct. 6, 2014 https://www.forgemag.com/articles/84265-grain-flow-in-forgings---the-basics
