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. Justin Mincey 1, Rongmei Niu 2, Yan Xin 2, Ke Han 2 1. Chemistry Department, Bethune-Cookman University, Daytona Beach, FL 32114 2. Division of Material.

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Presentation on theme: ". Justin Mincey 1, Rongmei Niu 2, Yan Xin 2, Ke Han 2 1. Chemistry Department, Bethune-Cookman University, Daytona Beach, FL 32114 2. Division of Material."— Presentation transcript:

1 . Justin Mincey 1, Rongmei Niu 2, Yan Xin 2, Ke Han 2 1. Chemistry Department, Bethune-Cookman University, Daytona Beach, FL Division of Material Science & Technology, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL Introduction & Objective Experimental & Methods Results & Discussion Conclusion References Acknowledgement Preparation: Cold Rolling: From initial thickness of 2.2 mm to 0.22mm with thickness reduction of 48%. Heat Treatment: The samples were annealed at 820˚C for 1 hour before next cold rolling and it reached 39% total reduction thickness The final rolled samples were aged at 500˚C for 2 hours. Buehler Mounting was used to create a mold or puck around the sample for easier analysis and handling to exam it on the SEM. The samples in the puck were grinded using silicon carbide grinding papers before placed on the Buehler Vibratory Polisher vibration for polishing for 5-6 hours using a mix of 0.25 alumina oxide powder and deionized water. Tensile sample strips were punched using a puncher. Maraging steels are high strength alloys. Their strength can reach up to 2500 MPa. These steels are a special class of low-carbon ultra-high- strength steels which derive their strength not from carbon, but from precipitation of inter-metallic compounds. The principal alloying element is 15 to 25% nickel. Secondary alloying elements are added to produce intermetallic precipitates, which include cobalt, molybdenum, and titanium. Original development was carried out on 20 and 25% Ni steels to which small additions of Al, Ti, and Nb were added. The balance of the alloying elements is Fe. Because of their high strength, the NHMFL is interested in using them as reinforcement materials for high field magnets [1]. However, before applications, significant amount of research is required. One of the areas is to understand if the thin strips or sheets can be made to reach strength in a range of higher than 2000 MPa. The REU program is part of this endeavor. Above: We made the puck with the sample and used the Instron Wilson Tukon 2100 Micro-Indentation. This uses a very small diamond tip to create indentations on the sample surface. This was to obtain hardness data for the samples. We found that the aged samples had hardness around 829 and the non-aged sample that had a hardness around 470. Energy dispersive x-ray spectrum in the SEM shows the elemental components of the sample being Co, Mo, Ti, Fe, and Ni, with 49wt%Co, 6wt%Mo, 0.7wt%Ti, 34wt%Fe and 10wt%Ni. Methods/Testing: Microindetation Chemical Etching of Maraging Steel - 95 mL of ethanol and 5 mL HNO 3 Scanning Electron Microscope (SEM) Tensile Test To the right: The colored graph shows the strain distributions of the material. The graph indicates an inhomogeneous stress distribution. Around file number 115 is where the stress starts giving away. Therefore, modified grips are required to measure the strain distributions. Below: The tensile samples of the Maraging Steel were place in the MTS to acquire the stress-strain curve. Currently, the stress-strain curve provides yield strength of 1700 MPa. However, the existing grips cannot withstand the stress of the materials. More tests are required to verify the results with modified grips. I would like to thank my mentor Dr. Yan Xin, for offering insight, guidance, expertise, and patience for my development as a future scientist. Also to Dr. Jun Lu, Dr. Ke Han, and Dr. Rongmei Niu; thank you for teaching all the different techniques for the labs. I also like to thank the Mr. Jose Sanchez and Ms. Patricia Dixon at National High Magnetic Field Laboratory of Florida State University for giving me the opportunity to be a part of this great REU program, I am truly grateful. To the following others: Dr. Alexis Brooks-Walter, Dr. Christopher A. Davis, Dr. Herbert Thompson and Faculty of SSEM, Bethune-Cookman University, Florida-Georgia Louis Stokes Alliance for Minority Participation (FGLSAMP). This work was funded by the NSF Cooperative Agreement DMR , NSF DMR , Florida State University and the National High Magnetic Field Laboratory. We have studied this 350 Maraging Steel that went through a cold rolling and aged heat treatment. We have found that the aged and cold rolled reached a hardness of 828 that gives a 76% over the sample that was non-aged. This show that when Maraging Steel increased strength after going through a aged heat treatment. Also, there is not a appreciable anisotropy along and perpendicular to the rolling directions. Tensile testing is not conclusive due to experimental difficulties because of the high strength of the materials, and further tensile testing are needed. [1] Han, K., Strength and Ductility of Nanostructured Composites with Co- Deformable Components (invited paper), Materials Science Forum, , (2010)


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