China
Africa
Explore chapters and articles related to this topic
2-D Based Nanostructures and Their Machining Challenges
Published in Subhash Singh, Dinesh Kumar, Fabrication and Machining of Advanced Materials and Composites, 2023
K. Santhosh Kumar, Subhash Singh
Certain polycrystalline materials at a particular temperature and strain rate demonstrated a greater plastic deformation (about 100–1000%) without any fracture or necking propagation. Such kinds of behaviour are called superplasticity, which characteristically arises in substances with ultra-fine grains and above their melting temperatures [26]. The rate of deformation that promotes the superplasticity nature is inversely proportionate to the square of the grain sizes. The thermal stability of 2-D nanostructures and deficit of grain growth should be contemplated for benefit of their superplastic behaviour.
Smart Machining Processes
Published in E. S. Gevorkyan, M. Rucki, V. P. Nerubatskyi, W. Żurowski, Z. Siemiątkowski, D. Morozow, A. G. Kharatyan, Remanufacturing and Advanced Machining Processes for New Materials and Components, 2022
E. S. Gevorkyan, M. Rucki, V. P. Nerubatskyi, W. Żurowski, Z. Siemiątkowski, D. Morozow, A. G. Kharatyan
Nanocrystalline (NC) materials with a grain size in the range of 1–100 nm have emerged as a new class of materials with unusual structures (Mohamed and Li, 2001). Because of such characteristics, these materials exhibit unique microstructures in which the volume of grain boundary is significant and affects various physical, electrical, chemical, magnetic, and deformation properties in the ultrafine grain size range. One of the most important features of NC materials is an interesting possibility to address the low strain rates of the superplastic region, usually 10−5 to 10−2 s−1, too slow to be economically suitable for a variety of industrial applications. Mohamed and Li (2001) emphasize that as the grain size decreases from micrometer to nanometer, the superplastic region can be transposed to high strain rates or observed at lower temperatures, exhibiting a high strain rate and/or low-temperature superplasticity. Wang, Jiang et al. (2020) report properties of bulk nanocrystalline Mg fabricated by cryomilling and spark plasma sintering with an average grain size of 74 nm. They note superplastic strain of ~120% during compression at room temperature with a strain rate of up to 10−2 s−1, as well as an increased strain rate sensitivity.
Hot Deformation Characteristics of Magnesium Alloys
Published in Leszek A. Dobrzański, George E. Totten, Menachem Bamberger, Magnesium and Its Alloys, 2020
Rajendra Laxman Doiphode, S.V.S. Narayana Murty, Bhagwati Prasad Kashyap
Study of high temperature flow properties is important for optimizing the manufacturing processes (4). Superplasticity is the ability of a polycrystalline material to exhibit, in a generally isotropic manner, very high elongations, and prior to failure. If the material is superplastic, then by using the required air/gas flow pressure, the products can be manufactured easily. This will improve the productivity. Under some limited experimental conditions, the material can be pulled out to exhibit a very large neck free elongation prior to failure. These high tensile elongations are examples of the occurrence of superplasticity.
Effects of CCEP and Sc on superplasticity of Al–5.6Mg–0.7Mn alloys
Published in Materials and Manufacturing Processes, 2018
Sheng-Long Lee, Chun-Hung Yen, Yu-Chih Tzeng, Jo-Kuang Nieh, Hui-Yun Bor, Gung-Hui Liu
Under the absolute melting temperature (Tm) and strain rate (10−5–10−3 s−1), a material can exhibit an extraordinarily large elongation called superplasticity. Superplasticity is divided into two types: internal stress and fine structure superplasticity. In general, superplastic behavior is achieved by grain boundary sliding in materials having very fine and equiaxed grains, wherein these grains are stable at high temperature and high-angle boundary conditions. Two typical routes of controlling the fine and stable grain structure in Al–Mg alloys are through addition of transition elements and technology process to control fine-grain formation.[12,13] The addition of trace amounts of Mn, Zr, and Sc elements during the production of an Al–Mg alloy can also effectively refine the grains in the cast ingot and improve the mechanical strength.[9,10,14,15] The beneficial effects of the combination of additions of Mn, Sc, and Zr to Al-based alloys in terms of improved precipitation and suppression of recrystallization have also attracted significant attention in the literature.[16,17] Of the aforementioned elements, Sc is compatible with the formation of Al3Sc phase during the casting process. The crystal structure is similar to that of α-Al, and it is beneficial to α-Al nucleation,[10,18,19] prompting grain refinement during the casting of the Al alloy.
Material model calibration for superplastic forming
Published in Inverse Problems in Science and Engineering, 2019
Superplasticity is the almost neck-free elongation of several hundreds of per cent that can be observed in some metals when a metal with certain metallurgical properties is strained at a certain strain rate and temperature. These metallurgical properties usually include small, equiaxed grains that are typically less than in diameter. Ti-6Al-4V exhibits superplastic behaviour at strain rates less than s−1 at temperatures greater than 900C [1].