Processing,microstructural characterization and mechanical properties of a Ti2AlC/nanocrystalline Mg-matrix composite |
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| Authors: | Shahram Amini Chaoying Ni Michel W Barsoum |
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| Affiliation: | 1. Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, United States;2. Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716, United States;1. Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics Engineering, College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China;2. National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials, School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;1. School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China;2. Center of Materials Science and Engineering, School of Mechanical and Electronic Control Engineering, Beijing Jiaotong University, Beijing, 100044, China;3. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China;4. National Engineering Research Center for Semiconductor Materials, General Research Institute for Nonferrous Metals, Beijing, 100088, China;1. School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China;2. Engineering Laboratory of Nuclear Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China;1. Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA;2. School of Civil Engineering, University of Sydney, Sydney, NSW 2006, Australia;3. Department of Material Science and Engineering, Texas A&M University, College Station, TX 77843, USA |
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| Abstract: | Herein we report on the processing and microstructural characterization of 50 vol.% Ti2AlC/nanocrystalline (nc) Mg-matrix composites fabricated by pressureless melt infiltration at 750 °C for 1 h. X-ray diffraction and transmission electron microscopy both confirmed that the Mg grain size was ～35 ± 15 nm. The microstructure was also exceptionally stable; annealing for 6 h at 550 °C did not alter the size of the Mg-grains. Some Mg was dissolved in the Ti2AlC confirming the existence of a (Ti1-xMgx)2AlC solid solution, with x as high as 0.2. A small amount of Ti (3 ± 1 at.%) was also found in the Mg matrix. At 350 ± 40 the ultimate tensile strength is significantly greater than other pure Mg composites reported in the literature. At 700 ± 10 MPa, the ultimate compressive stresses of these composites were ≈ 40% higher than those of a 50 vol.% Ti3SiC2–Mg or a 50 vol.% SiC–Mg, in which the Mg-matrix grains were not at the nanoscale. The Ti2AlC/nc-Mg composites are readily machinable, stiff (≈70 GPa), strong, light (2.9 g/cm3) and exhibited exceptional damping capabilities, that increased as the square of the applied stress to stress levels of the order of ≈ 500 MPa. The energy dissipated per cycle per unit volume at such stress levels is believed to be the highest ever reported for a crystalline solid and to be due to the formation and annihilation of incipient kink bands. The technological implications of having such solids are briefly discussed. |
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