Ultra-light Mg–Li alloy by design to achieve unprecedented high stiffness using the CALPHAD approach |
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| Affiliation: | 1. School of Materials Science & Engineering, Beijing Institute of Technology, No.5 South Zhongguancun Street, Haidian District, Beijing, 100081, China;2. Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, No. 5 South Zhongguancun Street, Haidian District, Beijing, 100081, China;1. SRC Thermochemistry of Materials, NUST MISIS, Leninsky prosp. 4, 119049, Moscow, Russia;2. Department of Chemistry, Lomonosov Moscow State University, 1-3 LeninskiyeGory, 119991, Moscow, Russia;3. Hampton Thermodynamics Ltd, Hampton Hill, Hampton, UK;1. College of Mechanical Engineering, Yangzhou University, Yangzhou, 225127, China;2. Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea;3. School of Mechanical and Automotive Engineering, Qilu University of Technology, Jinan, 250353, China;1. State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, School of Physical Science and Technology, Guangxi University, Nanning, 530004, China;2. Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China;3. Tech Institute of Advanced Materials & College of Materials Science and Engineering, Nanjing Tech University, Nanjing, 211816, China;4. State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, China |
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| Abstract: | Over decades, Mg–Li alloys have been widely used in aerospace industries owing to their low density (<1.65 g/cm3), medium strength (UTS: 130–200 MPa; YS: 100–170 MPa), and exceptional ductility (elongation: 5–30%). However, their stiffness is so poor (Young's Modulus: 45–47 GPa) that cannot meet many engineering design requirements such as space exploration and Lunar/Mars landing. Therefore, increasing modulus without degrading the strength and ductility of Mg–Li alloy has been a tough problem to be solved for many years. In this study, we have successfully made a significant breakthrough in improving the performance of Mg–Li alloys by inventing a new composition and a new processing route using CALPHAD for ultra-light Mg–Li alloys (density∼1.57 g/cm3), achieving high-strength (UTS: 335 MPa and YS: 290 MPa) and high-modulus (62.5 GPa). The origin of modulus improvement has been discovered by using a combination of SEM, TEM, XCT, nanoindentation, and neutron scattering experiments. Thermodynamically, it was found the high strength and modulus are attributed to the enhanced Mg–Mg bonding in the matrix and the increased elastic interaction forces from the lattice mismatch between the solute atoms and the solvent Mg. Meanwhile, the solution strengthening by lithium and precipitation hardening is discovered by inhibiting dislocation motion. Interestingly, age softening in Al–Li has been found to be a result of phase transformation from high-modulus particles into low ones using TEM, SANS, and nanoindentation tests. |
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| Keywords: | Mg-Li alloy Modulus Neutron scattering AlLi Nanoindentation Aging |
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