I. Brodova - Academia.edu (original) (raw)

Papers by I. Brodova

Physics of Metals and Metallography, 2020

The evolution of the structure and phase composition of the Al–Zn–Mg–Fe–Ni alloy (nikalin) during... more The evolution of the structure and phase composition of the Al–Zn–Mg–Fe–Ni alloy (nikalin) during severe plastic deformation by high pressure torsion and annealing has been investigated using high-resolution TEM techniques. The deformation of the quenched alloy has been found to result in a submicron composite comprising an Al matrix and various fine aluminides. The severe structural refinement takes place along with phase transformations, which dissolve the metastable Al3Zr-phase particles and cause the nanosized strengthening phases Т (Al2Mg3Zn3) and η' (MgZn2) to precipitate from the Al solid solution which has been supersaturated in result of quenching and deformation. Nikalin has been determined to retain its submicrocrystalline state during low-temperature annealing (200°C, 4 h) due to the barrier effect of fine hardening phase particles, fixing grain boundaries. High-temperature heating to 400°C for four hours transfers nikalin to the overaged state, in which it is characterized to consist of a recrystallized matrix with grains 2–3 µm in size, eutectic micron-sized aluminides, and stable Al2Mg3Zn3 and MgZn2-phase particles with sizes of no more or equal to 500 nm.

Physics of Metals and Metallography, 1998

Physics of Metals and Metallography, 2017

⎯The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical com... more ⎯The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical composition was 4.4Mg-0.6Mn-0.11Si-0.23Fe-0.03Cr-0.02Cu-0.06Ti wt % and Al base) under shockwave compression are presented. The submicrocrystalline structure of the alloy was produced in the process of dynamic channel-angular pressing at a strain rate of 10 4 s-1. The average size of crystallites in the alloy was 180-460 nm. Hugoniot elastic limit σ HEL , dynamic yield stress σ y , and the spall strength σ SP of the submicrocrystalline alloy were determined based on the free-surface velocity profiles of samples during shock compression. It has been established that upon shock compression, the σ HEL and σ y of the submicrocrystalline alloy are higher than those of the coarse-grained alloy and σ sp does not depend on the grain size. The maximum value of σ HEL reached for the submicrocrystalline alloy is 0.66 GPa, which is greater than that in the coarse-crystalline alloy by 78%. The dynamic yield stress is σ y = 0.31 GPa, which is higher than that of the coarse-crystalline alloy by 63%. The spall strength is σ sp = 1.49 GPa. The evolution of the submicrocrystalline structure of the alloy during shock compression was studied. It has been established that a mixed nonequilibrium grain-subgrain structure with a fragment size of about 400 nm is retained after shock compression, and the dislocation density and the hardness of the alloy are increased.

Physics of Metals and Metallography

Physics of Metals and Metallography, 2002

A new approach was employed to create a metastable supersaturated solid solution of iron in alumi... more A new approach was employed to create a metastable supersaturated solid solution of iron in aluminum and to form a precipitation-strengthened ultrafine-grained (UFG) structure in the rapidly quenched Al-5 wt % Fe alloy using severe plastic deformation (SPD) by torsion under a high pressure. In the process of short-term heating in a temperature range of 20-450°C, structural changes in the samples thus deformed were studied by transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry. An UFG structure that consists of a supersaturated solid solution of iron in aluminum with an average grain size of 150 nm and refined intermetallic particles was shown to form in the hypereutectic two-phase alloy due to rapid quenching and SPD. The aging regimes that bring about a maximum strength of the alloy were determined. Time and temperature dependences of the microhardness were studied. It was shown that the high-strength state in the alloy may be realize...

The structure of ingots of Al-Si-based casting alloys obtained using an original technique by sme... more The structure of ingots of Al-Si-based casting alloys obtained using an original technique by smelting silumins in molten haloids is discussed. The effects of the composition of ionic melts on the solidification of silumins are studied, the advantages of the new method of casting are described, and a new mechanism for the modification of the structure of castings is suggested.

Physics of Metals and Metallography, 2018

The structure and the mechanical and electrical properties of new ternary composites based on Al-... more The structure and the mechanical and electrical properties of new ternary composites based on Al-Mg deformable alloy obtained by fluid extrusion are studied. The evolution of structural and phase transformations in dissimilar fibers (Cu, Mg, and Al-Mg alloy) during thermomechanical treatment are studied using the methods of metallography, scanning electron microscopy, and hardness measurements. It is established that the strengthening of the ternary composite results from solid state reactions at the boundaries of the fiber, which lead to the formation of intermetallide phases (AlCu, Al 2 Cu, Mg 2 Cu, and MgCu 2) and nonequilibrium supersaturated solid solutions of copper in aluminum and magnesium.

Materials Science and Engineering: A, 2003

A process for increasing both strength and ductility in a brittle Al Á/5 wt.% Fe alloy by Equal C... more A process for increasing both strength and ductility in a brittle Al Á/5 wt.% Fe alloy by Equal Channel Angular Pressing (ECAP) was investigated. The increase in solid solubility of iron in the Al matrix produced by intense deformation under ECAP permitted age hardening in this alloy although it is not hardenable by conventional processing. An ultrafine-grained microstructure of 325 Á/ 450 nm was obtained in a brittle, cast Al Á/5 wt.% Fe alloy by ECAP with various numbers of passes and backpressure levels from 40 to 275 MPa. A supersaturated solid solution with a maximum solubility of 0.6 wt.% of iron in an aluminium matrix was obtained during ECAP, which allowed ageing of the conventionally non-hardenable alloy. Strength, ductility and microhardness of the cast alloy processed by the ECAP technique were significantly enhanced (e.g. strength and ductility from 102 MPa and 3.4% to 261 MPa and 5.8%, respectively). The subsequent artificial ageing resulted in a further increase in strength to 272 MPa. It was shown by scanning electron microscopy (SEM) that the type of fracture of tensile specimens taken from material subjected to ECAP was predominantly ductile. An increase in backpressure retards cracking of intermetallic particles and enhances the workability and ductility of such alloys processed by ECAP.

Physics of Metals and Metallography, 2019

Metal Science and Heat Treatment

The methods of metallographic, differential thermal and x-ray phase analysis, light and electron ... more The methods of metallographic, differential thermal and x-ray phase analysis, light and electron microscopy, and measurement of microhardness are used to study the morphological features of the structure of hypereutectic alloy Al – 30 at.% Cu formed due to cooling of liquid phase at a rate of about 2 and about 104 K/sec after superheating above the liquidus. A comparative study of structural and phase transformations in castings is performed.

Physics of Metals and Metallography

Letters on Materials

An experimental evidence of deformation twinning in coarse-grained aluminium is presented for the... more An experimental evidence of deformation twinning in coarse-grained aluminium is presented for the first time using electron backscatter diffraction technique. This phenomenon occurs when using a novel method of severe plastic deformation referred to as dynamic channel angular pressing. A pressing die had two channels of equal cross-sections intersecting at an angle of 90°. A special gun accelerated the sample up to the speed of 100 m s-1 and directed it into the die. As a result, the strain rate was about 10 5 s-1. Twin-oriented mesobands of 3 to 20 μm in width appear predominantly near grain boundaries after deformation. Crystallographic characteristics of the mesobands formed in two different grains were examined in detail. Analysis of a deviation of their misorientations from the ideal twin misorientation showed that the first mesoband family could be formed at an early stage of the first pass of the dynamic channel angular pressing, while the second family-at a later stage. The mesobands were suggested to form by successive nucleation and coalescence of microscopic twins during the shear localization. Results have shown that in aluminum, which is characterized by higher stacking fault energy and higher dislocation mobility, deformation twinning occurs only under high strain-rate dynamic deformation.

Metal Science and Heat Treatment, 2008

ABSTRACT The main regular changes in the structure of aluminum alloys with transition metals in a... more ABSTRACT The main regular changes in the structure of aluminum alloys with transition metals in a wide range of crystallization conditions are considered depending on the structural state of their melts. The effect of complex treatment (rapid hardening and torsional severe plastic deformation under pressure) on formation of nanostructured alloys is considered.

Letters on Materials, 2013

Metal Science and Heat Treatment, 2015

Crystallization kinetics of Mg 84 Ni 12.5 Y 3.5 amorphous ribbons produced by the melt-spinning m... more Crystallization kinetics of Mg 84 Ni 12.5 Y 3.5 amorphous ribbons produced by the melt-spinning method, was studied by DSC analysis and X-ray diffraction. The effect of heating rate (from 2 to 240 K min -1 ) was investigated in the temperature range from 298 to 673 K. The results showed that the crystallization process took place in two stages: a) crystallization of part of the amorphous matrix to an intermediate phase and hcp-Mg, and b) transformation of the intermediate phase and the remaining amorphous material to Mg 2 Ni+Mg (solid solution of Y in Mg). Increasing the heating rate from 2 to 240 K min -1 results in increases of the temperature difference between the twostep crystallization of the first stage transformation processes from 33 to 56 K and in increases of the temperature difference between the two-stage transformation from 62 to 97 K.

Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2008

ABSTRACT Processes of structure formation in iron-containing silumins remelted in a salt melt are... more ABSTRACT Processes of structure formation in iron-containing silumins remelted in a salt melt are analyzed. The effects of the chemical composition and temperature-time characteristics of the ionic medium on the phase composition of metallic materials are studied. The salt melt-silumin system is modeled in thermodynamic terms.

Journal of Physics: Conference Series, 2008

Processes of structure formation in iron-containing silumins made by smelting in a salt melt are ... more Processes of structure formation in iron-containing silumins made by smelting in a salt melt are studied. The effect of the composition and the temperature-time characteristics of the ionic medium on the phase composition of metallic materials is analyzed. The ‘salt melt - silumin’ system is simulated in thermodynamic terms.

Journal of Physics: Conference Series, 2008

ABSTRACT The technique of rotating oscillation damping of a crucible filled in with the melt unde... more ABSTRACT The technique of rotating oscillation damping of a crucible filled in with the melt under investigation was used for measurement of viscosity of the Mg-based AZ91D commercial alloy with various additions of calcium. The viscosity was measured in liquid state in temperature interval from 600 up to 840°C. The comparative metallographic investigation of the structure of samples with calcium content of 0.0, 0.4, 0.6 and 0.8 wt.% which were crystallized just after re-melting at the temperature of 640°C and after heating in liquid state up to 850°C were made. It was shown that the thermal treatment of samples in liquid state is accompanied by considerable changes in the cast structure that forms after the crystallization of the samples.

Le Journal de Physique IV, 2000

ABSTRACT The dimensions of characteristic zones of transformations related to the high-strain-rat... more ABSTRACT The dimensions of characteristic zones of transformations related to the high-strain-rate deformation of the alloy in the solid state and its melting in stress waves, as well as partial evaporation of the shocked melt during unloading into the central cavity that is formed behind the front of a spherically divergent shock wave have been determined. The chosen regime of the explosive loading of the sphere led to melting at the isentrope and at the adiabat in shock waves in various zones along the radius, and to the subsequent formation of two zones with "cast" structures differing in the grain size, degree of supersaturation of the α-solid solution, and the size and shape of the precipitated aluminide particles. In the zone that undenvent melting and high-rate solidification, metastable aluminides A13Hf were revealed inside the adiabatic shear bands. The main features of the evolution of the structures of the matrix and the aluminides in the field of the solid-state transformation were revealed. As a result of high-rate loading and subsequent unloading, the brittle phase was shown to undergo fragmentation and fracture, while the aluminum matrix acquires the structure of a hot-worked material.

Physics of Metals and Metallography, 2020

The evolution of the structure and phase composition of the Al–Zn–Mg–Fe–Ni alloy (nikalin) during... more The evolution of the structure and phase composition of the Al–Zn–Mg–Fe–Ni alloy (nikalin) during severe plastic deformation by high pressure torsion and annealing has been investigated using high-resolution TEM techniques. The deformation of the quenched alloy has been found to result in a submicron composite comprising an Al matrix and various fine aluminides. The severe structural refinement takes place along with phase transformations, which dissolve the metastable Al3Zr-phase particles and cause the nanosized strengthening phases Т (Al2Mg3Zn3) and η' (MgZn2) to precipitate from the Al solid solution which has been supersaturated in result of quenching and deformation. Nikalin has been determined to retain its submicrocrystalline state during low-temperature annealing (200°C, 4 h) due to the barrier effect of fine hardening phase particles, fixing grain boundaries. High-temperature heating to 400°C for four hours transfers nikalin to the overaged state, in which it is characterized to consist of a recrystallized matrix with grains 2–3 µm in size, eutectic micron-sized aluminides, and stable Al2Mg3Zn3 and MgZn2-phase particles with sizes of no more or equal to 500 nm.

Physics of Metals and Metallography, 1998

Physics of Metals and Metallography, 2017

⎯The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical com... more ⎯The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical composition was 4.4Mg-0.6Mn-0.11Si-0.23Fe-0.03Cr-0.02Cu-0.06Ti wt % and Al base) under shockwave compression are presented. The submicrocrystalline structure of the alloy was produced in the process of dynamic channel-angular pressing at a strain rate of 10 4 s-1. The average size of crystallites in the alloy was 180-460 nm. Hugoniot elastic limit σ HEL , dynamic yield stress σ y , and the spall strength σ SP of the submicrocrystalline alloy were determined based on the free-surface velocity profiles of samples during shock compression. It has been established that upon shock compression, the σ HEL and σ y of the submicrocrystalline alloy are higher than those of the coarse-grained alloy and σ sp does not depend on the grain size. The maximum value of σ HEL reached for the submicrocrystalline alloy is 0.66 GPa, which is greater than that in the coarse-crystalline alloy by 78%. The dynamic yield stress is σ y = 0.31 GPa, which is higher than that of the coarse-crystalline alloy by 63%. The spall strength is σ sp = 1.49 GPa. The evolution of the submicrocrystalline structure of the alloy during shock compression was studied. It has been established that a mixed nonequilibrium grain-subgrain structure with a fragment size of about 400 nm is retained after shock compression, and the dislocation density and the hardness of the alloy are increased.

Physics of Metals and Metallography

Physics of Metals and Metallography, 2002

A new approach was employed to create a metastable supersaturated solid solution of iron in alumi... more A new approach was employed to create a metastable supersaturated solid solution of iron in aluminum and to form a precipitation-strengthened ultrafine-grained (UFG) structure in the rapidly quenched Al-5 wt % Fe alloy using severe plastic deformation (SPD) by torsion under a high pressure. In the process of short-term heating in a temperature range of 20-450°C, structural changes in the samples thus deformed were studied by transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry. An UFG structure that consists of a supersaturated solid solution of iron in aluminum with an average grain size of 150 nm and refined intermetallic particles was shown to form in the hypereutectic two-phase alloy due to rapid quenching and SPD. The aging regimes that bring about a maximum strength of the alloy were determined. Time and temperature dependences of the microhardness were studied. It was shown that the high-strength state in the alloy may be realize...

The structure of ingots of Al-Si-based casting alloys obtained using an original technique by sme... more The structure of ingots of Al-Si-based casting alloys obtained using an original technique by smelting silumins in molten haloids is discussed. The effects of the composition of ionic melts on the solidification of silumins are studied, the advantages of the new method of casting are described, and a new mechanism for the modification of the structure of castings is suggested.

Physics of Metals and Metallography, 2018

The structure and the mechanical and electrical properties of new ternary composites based on Al-... more The structure and the mechanical and electrical properties of new ternary composites based on Al-Mg deformable alloy obtained by fluid extrusion are studied. The evolution of structural and phase transformations in dissimilar fibers (Cu, Mg, and Al-Mg alloy) during thermomechanical treatment are studied using the methods of metallography, scanning electron microscopy, and hardness measurements. It is established that the strengthening of the ternary composite results from solid state reactions at the boundaries of the fiber, which lead to the formation of intermetallide phases (AlCu, Al 2 Cu, Mg 2 Cu, and MgCu 2) and nonequilibrium supersaturated solid solutions of copper in aluminum and magnesium.

Materials Science and Engineering: A, 2003

A process for increasing both strength and ductility in a brittle Al Á/5 wt.% Fe alloy by Equal C... more A process for increasing both strength and ductility in a brittle Al Á/5 wt.% Fe alloy by Equal Channel Angular Pressing (ECAP) was investigated. The increase in solid solubility of iron in the Al matrix produced by intense deformation under ECAP permitted age hardening in this alloy although it is not hardenable by conventional processing. An ultrafine-grained microstructure of 325 Á/ 450 nm was obtained in a brittle, cast Al Á/5 wt.% Fe alloy by ECAP with various numbers of passes and backpressure levels from 40 to 275 MPa. A supersaturated solid solution with a maximum solubility of 0.6 wt.% of iron in an aluminium matrix was obtained during ECAP, which allowed ageing of the conventionally non-hardenable alloy. Strength, ductility and microhardness of the cast alloy processed by the ECAP technique were significantly enhanced (e.g. strength and ductility from 102 MPa and 3.4% to 261 MPa and 5.8%, respectively). The subsequent artificial ageing resulted in a further increase in strength to 272 MPa. It was shown by scanning electron microscopy (SEM) that the type of fracture of tensile specimens taken from material subjected to ECAP was predominantly ductile. An increase in backpressure retards cracking of intermetallic particles and enhances the workability and ductility of such alloys processed by ECAP.

Physics of Metals and Metallography, 2019

Metal Science and Heat Treatment

The methods of metallographic, differential thermal and x-ray phase analysis, light and electron ... more The methods of metallographic, differential thermal and x-ray phase analysis, light and electron microscopy, and measurement of microhardness are used to study the morphological features of the structure of hypereutectic alloy Al – 30 at.% Cu formed due to cooling of liquid phase at a rate of about 2 and about 104 K/sec after superheating above the liquidus. A comparative study of structural and phase transformations in castings is performed.

Physics of Metals and Metallography

Letters on Materials

An experimental evidence of deformation twinning in coarse-grained aluminium is presented for the... more An experimental evidence of deformation twinning in coarse-grained aluminium is presented for the first time using electron backscatter diffraction technique. This phenomenon occurs when using a novel method of severe plastic deformation referred to as dynamic channel angular pressing. A pressing die had two channels of equal cross-sections intersecting at an angle of 90°. A special gun accelerated the sample up to the speed of 100 m s-1 and directed it into the die. As a result, the strain rate was about 10 5 s-1. Twin-oriented mesobands of 3 to 20 μm in width appear predominantly near grain boundaries after deformation. Crystallographic characteristics of the mesobands formed in two different grains were examined in detail. Analysis of a deviation of their misorientations from the ideal twin misorientation showed that the first mesoband family could be formed at an early stage of the first pass of the dynamic channel angular pressing, while the second family-at a later stage. The mesobands were suggested to form by successive nucleation and coalescence of microscopic twins during the shear localization. Results have shown that in aluminum, which is characterized by higher stacking fault energy and higher dislocation mobility, deformation twinning occurs only under high strain-rate dynamic deformation.

Metal Science and Heat Treatment, 2008

ABSTRACT The main regular changes in the structure of aluminum alloys with transition metals in a... more ABSTRACT The main regular changes in the structure of aluminum alloys with transition metals in a wide range of crystallization conditions are considered depending on the structural state of their melts. The effect of complex treatment (rapid hardening and torsional severe plastic deformation under pressure) on formation of nanostructured alloys is considered.

Letters on Materials, 2013

Metal Science and Heat Treatment, 2015

Crystallization kinetics of Mg 84 Ni 12.5 Y 3.5 amorphous ribbons produced by the melt-spinning m... more Crystallization kinetics of Mg 84 Ni 12.5 Y 3.5 amorphous ribbons produced by the melt-spinning method, was studied by DSC analysis and X-ray diffraction. The effect of heating rate (from 2 to 240 K min -1 ) was investigated in the temperature range from 298 to 673 K. The results showed that the crystallization process took place in two stages: a) crystallization of part of the amorphous matrix to an intermediate phase and hcp-Mg, and b) transformation of the intermediate phase and the remaining amorphous material to Mg 2 Ni+Mg (solid solution of Y in Mg). Increasing the heating rate from 2 to 240 K min -1 results in increases of the temperature difference between the twostep crystallization of the first stage transformation processes from 33 to 56 K and in increases of the temperature difference between the two-stage transformation from 62 to 97 K.

Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2008

ABSTRACT Processes of structure formation in iron-containing silumins remelted in a salt melt are... more ABSTRACT Processes of structure formation in iron-containing silumins remelted in a salt melt are analyzed. The effects of the chemical composition and temperature-time characteristics of the ionic medium on the phase composition of metallic materials are studied. The salt melt-silumin system is modeled in thermodynamic terms.

Journal of Physics: Conference Series, 2008

Processes of structure formation in iron-containing silumins made by smelting in a salt melt are ... more Processes of structure formation in iron-containing silumins made by smelting in a salt melt are studied. The effect of the composition and the temperature-time characteristics of the ionic medium on the phase composition of metallic materials is analyzed. The ‘salt melt - silumin’ system is simulated in thermodynamic terms.

Journal of Physics: Conference Series, 2008

ABSTRACT The technique of rotating oscillation damping of a crucible filled in with the melt unde... more ABSTRACT The technique of rotating oscillation damping of a crucible filled in with the melt under investigation was used for measurement of viscosity of the Mg-based AZ91D commercial alloy with various additions of calcium. The viscosity was measured in liquid state in temperature interval from 600 up to 840°C. The comparative metallographic investigation of the structure of samples with calcium content of 0.0, 0.4, 0.6 and 0.8 wt.% which were crystallized just after re-melting at the temperature of 640°C and after heating in liquid state up to 850°C were made. It was shown that the thermal treatment of samples in liquid state is accompanied by considerable changes in the cast structure that forms after the crystallization of the samples.

Le Journal de Physique IV, 2000

ABSTRACT The dimensions of characteristic zones of transformations related to the high-strain-rat... more ABSTRACT The dimensions of characteristic zones of transformations related to the high-strain-rate deformation of the alloy in the solid state and its melting in stress waves, as well as partial evaporation of the shocked melt during unloading into the central cavity that is formed behind the front of a spherically divergent shock wave have been determined. The chosen regime of the explosive loading of the sphere led to melting at the isentrope and at the adiabat in shock waves in various zones along the radius, and to the subsequent formation of two zones with "cast" structures differing in the grain size, degree of supersaturation of the α-solid solution, and the size and shape of the precipitated aluminide particles. In the zone that undenvent melting and high-rate solidification, metastable aluminides A13Hf were revealed inside the adiabatic shear bands. The main features of the evolution of the structures of the matrix and the aluminides in the field of the solid-state transformation were revealed. As a result of high-rate loading and subsequent unloading, the brittle phase was shown to undergo fragmentation and fracture, while the aluminum matrix acquires the structure of a hot-worked material.