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Shift of the phase equilibria in nanograined materials
Shift of the phase equilibria in nanograined materials, Mehaanikateaduskond, Lembit Kommel.
Shift of the phase equilibria in nanograined materials
Shift of the phase equilibria in nanograined materials
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Severe plastic deformation (SPD) is a novel materials processing technique which allows producing bulk nanomaterials. In addition to significant grain refinement, SPD also causes phase transformations in the material during treatment (at ambient temperature and during short processing times). SPD can induce the decomposition of a supersaturated solid solution, dissolution of phases, amorphization of crystalline phases, synthesis of the low-temperature allotropic modifications, and nanocrystallization in the amorphous matrix. The fundamental goal of the project is to find a common denominator of these seemingly contradictory processes. The aim is to be able to predict the changes in phase composition caused by the SPD. For this purpose the concept of effective temperature (shift of the phase equilibria) originally developed for materials under severe irradiation will be used for the SPD. The investigations will be performed on the NdFeB-based hard magnetic materials, NiTi- and CuAlNi-ba
Severe plastic deformation (SPD) is a novel materials processing technique which allows producing bulk nanomaterials. In addition to significant grain refinement, SPD also causes phase transformations in the material during treatment (at ambient temperature and during short processing times). SPD can induce the decomposition of a supersaturated solid solution, dissolution of phases, amorphization of crystalline phases, synthesis of the low-temperature allotropic modifications, and nanocrystallization in the amorphous matrix. The fundamental goal of the project is to find a common denominator of these seemingly contradictory processes. The aim is to be able to predict the changes in phase composition caused by the SPD. For this purpose the concept of effective temperature (shift of the phase equilibria) originally developed for materials under severe irradiation will be used for the SPD. The investigations will be performed on the NdFeB-based hard magnetic materials, NiTi- and CuAlNi-ba
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Partner 3. Dr. Lembit Kommel / Tallinn University of Technology, Tallinn, Estonia
The team of Dr. Kommel (7 members): Dr. Valdek Mikli, Dr. Irina Hussainova, Dr. Mart Viljus, Dr. Olga Volobueva, Dr. Mart Saarna, and M.Sc. Rainer Traksmaa. The general objective of present project is design via SPD the nanomaterials with improved mechanical and physical properties. The research is complemented by revealing the principal mechanisms of the evolution of microstructure and properties of ultrahigh-strength nanostructured metals, composites and alloys reinforced by CNT-s (via powder compaction). New precipitations/crystallites nucleation and growth at SPD and driving the solid state step-by-step heat treatment will utilized for additional increase of mechanical properties via interdiffusion processes between phases, phase transformation, phase equilibria, etc. Depending on cumulative strain [1, 2] the dislocations density in pure niobium (Nb) varies from 5.0E+10 to 2.0E+11 cm-2 and it was maximal for Nb which has minimal electrical conductivity, maximal value of hkl-parameter and maximal microstresses at atomic level. As a result of hard cyclic viscoplastic (HCV) deformation [3-5] of UFG pure copper the HAGB-s microstructure with low dislocation density will formed, electrical conductivity increased up to 103% IACS and impact toughness, ductility and viscoplasticity properties as well as uniform elongation at tension improved.
The team of Dr. Kommel will lead the Task 6 “Characterization of mechanical properties.” The static mechanical tests will be performed (tension tests) as well as cyclic fatigue tests. Team 2 will also perform the SPD of the CuCr- and CuHf- based alloys using the ECAP. The data obtained by Partner 6 will also be used by Partner 2 in their MD, MC and KMC modelling and by Partner 5 in their calculations based on statistical mechanics (polycluster models). The team of Prof. Kommel has long year-experience in collaboration with Coordinator team.
List of recent relevant publications
1. L. Kommel, V. Mikli, R. Traksmaa, M. Saarna, A. Pokatilov, S. Pikker, I. Kommel, Influence of the SPD processing features on the nanostructure and properties of a pure niobium. Mater. Sci. Forum 667-669 (2011) 785-790.
2. L. Kommel, N. Laev, Mechanism for single crystal refinement in high purity niobium during equal-channel angular pressing. Mater. Sci. (Medžiagotyra) 14-4 (2008) 319-323.
3. L. Kommel, Properties development of ultrafine-grained copper under hard cyclic viscoplastic deformation. Mater. Letters 64 (2010) 1580-1582.
4. L. Kommel, Metals microstructure improving under hard cyclic viscoplastic deformation. Mater. Sci. Forum 584-586 (2008) 361-366.
5. L. Kommel, I. Hussainova, O. Volobueva, Microstructure and properties development of copper during severe plastic deformation. Mater. & Design 28 (2007) 2121-2128.
The Partner has different ECAP set-ups for bulk metals, alloys and composites (two ECAP dies with circular, 16 mm and square, 14.5x14.5 mm, cross-sections of channels. The channels of ECAP die intersect under angle of  = 90°. The new designed multi-pass angular pressing (MPAP) die has three with step-by-step decreased channels which are interbreed under angle of  = 120°. The processed samples have length of 120-140 mm. The ECAP die has electrical pre-heating up to temperature of 500 °C. For study of mechanical properties the servo hydraulic dynamic and fatigue testing systems INSTRON-8516 (100 kN), Hardness- and Universal hardness testers (Zwick/Roell etc.), Nanoindentation tester (NanoTest NTX testing centre, Micro Materials Ltd.) are available.
Partner 3. Dr. Lembit Kommel / Tallinn University of Technology, Tallinn, Estonia
The team of Dr. Kommel (7 members): Dr. Valdek Mikli, Dr. Irina Hussainova, Dr. Mart Viljus, Dr. Olga Volobueva, Dr. Mart Saarna, and M.Sc. Rainer Traksmaa. The general objective of present project is design via SPD the nanomaterials with improved mechanical and physical properties. The research is complemented by revealing the principal mechanisms of the evolution of microstructure and properties of ultrahigh-strength nanostructured metals, composites and alloys reinforced by CNT-s (via powder compaction). New precipitations/crystallites nucleation and growth at SPD and driving the solid state step-by-step heat treatment will utilized for additional increase of mechanical properties via interdiffusion processes between phases, phase transformation, phase equilibria, etc. Depending on cumulative strain [1, 2] the dislocations density in pure niobium (Nb) varies from 5.0E+10 to 2.0E+11 cm-2 and it was maximal for Nb which has minimal electrical conductivity, maximal value of hkl-parameter and maximal microstresses at atomic level. As a result of hard cyclic viscoplastic (HCV) deformation [3-5] of UFG pure copper the HAGB-s microstructure with low dislocation density will formed, electrical conductivity increased up to 103% IACS and impact toughness, ductility and viscoplasticity properties as well as uniform elongation at tension improved.
The team of Dr. Kommel will lead the Task 6 “Characterization of mechanical properties.” The static mechanical tests will be performed (tension tests) as well as cyclic fatigue tests. Team 2 will also perform the SPD of the CuCr- and CuHf- based alloys using the ECAP. The data obtained by Partner 6 will also be used by Partner 2 in their MD, MC and KMC modelling and by Partner 5 in their calculations based on statistical mechanics (polycluster models). The team of Prof. Kommel has long year-experience in collaboration with Coordinator team.
List of recent relevant publications
1. L. Kommel, V. Mikli, R. Traksmaa, M. Saarna, A. Pokatilov, S. Pikker, I. Kommel, Influence of the SPD processing features on the nanostructure and properties of a pure niobium. Mater. Sci. Forum 667-669 (2011) 785-790.
2. L. Kommel, N. Laev, Mechanism for single crystal refinement in high purity niobium during equal-channel angular pressing. Mater. Sci. (Medžiagotyra) 14-4 (2008) 319-323.
3. L. Kommel, Properties development of ultrafine-grained copper under hard cyclic viscoplastic deformation. Mater. Letters 64 (2010) 1580-1582.
4. L. Kommel, Metals microstructure improving under hard cyclic viscoplastic deformation. Mater. Sci. Forum 584-586 (2008) 361-366.
5. L. Kommel, I. Hussainova, O. Volobueva, Microstructure and properties development of copper during severe plastic deformation. Mater. & Design 28 (2007) 2121-2128.
The Partner has different ECAP set-ups for bulk metals, alloys and composites (two ECAP dies with circular, 16 mm and square, 14.5x14.5 mm, cross-sections of channels. The channels of ECAP die intersect under angle of  = 90°. The new designed multi-pass angular pressing (MPAP) die has three with step-by-step decreased channels which are interbreed under angle of  = 120°. The processed samples have length of 120-140 mm. The ECAP die has electrical pre-heating up to temperature of 500 °C. For study of mechanical properties the servo hydraulic dynamic and fatigue testing systems INSTRON-8516 (100 kN), Hardness- and Universal hardness testers (Zwick/Roell etc.), Nanoindentation tester (NanoTest NTX testing centre, Micro Materials Ltd.) are available.