In the present study we report the changes in the modified near-surface layer on NiTi shape memor... more In the present study we report the changes in the modified near-surface layer on NiTi shape memory alloy, caused by ion implantation as well as their influence on the structure and mechanical properties of this material. Experimental results of an inhomogeneous structure and tribological properties of implanted NiTi are discussed in this paper.
This paper reports the application of nitrogen ion implantation for modification of a shape memor... more This paper reports the application of nitrogen ion implantation for modification of a shape memory alloy. It is known that the problem of creating a protective surface coating for the shape memory alloy is the most acute for potential applications of this material. Thus, the problem of increasing surface protective properties and, at the same time, simultaneous preservation of functional properties of shape memory materials is a subject of research and development [Pelletier H, Muller D, Mille P, Grob J. Surf Coat Technol 2002;158:309.]. The surface characterization of nitrogen implanted (fluence 1018 cm_2 and energy 50 keV) equiatomic commercial NiTi alloy samples was performed with the assistance of high resolution transmission electron microscopy (HTEM) techniques and modifications of phase composition before and after irradiation are studied at room and martensitic transformation temperatures by X-ray diffraction methods. Differential scanning calorimetry (DSC, TA Instruments) was used to characterize the transformation sequence and transformation temperatures for the initial and surface-modified materials. Experimental results of an inhomogeneous structure of near-surface layers in the ionimplanted NiTi alloy are discussed in this paper.
In this work (Ti,Si,Al)N films were deposited using only rf or a combination of rf and d.c. react... more In this work (Ti,Si,Al)N films were deposited using only rf or a combination of rf and d.c. reactive magnetron sputtering. Chemical composition, thickness, film structure and mechanical properties of the films were investigated by means of Rutherford backscattering (RBS), electron microprobe analysis (EPMA), ball-cratering, X-ray diffraction (XRD) and ultramicroindentation, respectively. All samples showed high hardness values, exceeding, in some cases, 50 GPa. XRD results revealed the formation of a mixture of two phases whose structure is similar to TiN. One phase is noted as being TiN bulk with a lattice parameter of 0.428 nm and develops only in conditions of high surface mobility. This behaviour can be associated with the segregation of the SiN phase, though the formation of an amorphous AlN phase cannot be excluded. Another phase, which is noted as Ti-Si-Al-N x (af0.420 nm), where Si and Al atoms substitute the Ti atoms on the TiN lattice, develops in situations of lower surface mobility. The thermal stability of these coatings was studied by thermal treatments in a vacuum atmosphere, where it was found that a small increase in hardness was obtained after 1 h heat treatment at 8008C. ᮊ
Cold-consolidation using high pressure torsion (HPT) has been applied to ball-milled Fe-based amo... more Cold-consolidation using high pressure torsion (HPT) has been applied to ball-milled Fe-based amorphous ribbons to process bulk disks of approximately 9 mm in diameter and 0.3 mm in thickness. The mainly amorphous bulk samples demonstrated soft magnetic behavior, higher Curie temperature and enhanced microhardness with respect to the ribbons.
Transactions of Nonferrous Metals Society of China, 2010
A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to p... more A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to produce thixo-casts from steel. After inductive heating to the required semi-solid temperature range, the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die. Bearing steel 100Cr6 (after forging) was used as the feedstock material. The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 µm and 8 µm. Differential scanning calorimetry (DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 ˚C which was attributed to about 45% of a liquid phase. With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 µm to 40 µm. The microstructure of globules indicated predominant presence of martensite (about 76% volume fraction) with residual austenite between plates. X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite. The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60, which confirms the presence of martensite and carbides. The thixo-casts were subjected to low tempering, at temperature of 150 ˚C for a period of 2 h, in order to remove stresses created during the process of thixoforming and to increase plasticity. The hardness after tempering was HRC 62.3. Additionally, in order to identify phases present in the thixo-casts, transmission electron microscopy (TEM) was carried out.
This paper summarizes theoretical and experimental studies of cBN–Zr composites of cBN:Zr molar r... more This paper summarizes theoretical and experimental studies of cBN–Zr composites of cBN:Zr molar ratio equal 9:1. From theoretical calculations it follows that Zr reacts with cBN in the full range of pressure (1·3×10−3–1×107 Pa) for temperatures 950 and 1750°C to form at two new phases: ZrB2 and ZrN whose amount depends on the conditions of synthesis. Experimentally, composite based on cubic boron nitride (cBN) with zirconium addition used as a binding material was prepared by high pressure hot pressing. Samples before and after heat treatment were characterized using transmission electron microscope. The TEM showed that after sintering a thin zone of fine ZrB2 and ZrN crystallites was formed at the cBN/Zr interface. After additional heat treatment the ZrN crystallites grew forming a layer up to 2 mm thick built from columnar grains of 0·1–0·2 mm in diameter. The ZrB2 remained as a thin (0·1 to 0·2 μm) layer of very fine equiaxial crystallites between the ZrN and cBN. The hardness of such sintered material was 20 GPa/HK1, after additional heat treatment at 950°C for 1h in vacuum of 3×10−3 Pa the hardness increased up to 29 GPa/HK1.
Two Ni-Ti-Zr -based amorphous ribbons of compositions Ni 56 Cu 2 Zr 18 Ti 16 Al 3 Si 5 and Ni 36 ... more Two Ni-Ti-Zr -based amorphous ribbons of compositions Ni 56 Cu 2 Zr 18 Ti 16 Al 3 Si 5 and Ni 36 Cu 23 Zr 18 Ti 14 Al 5 Si 4 were prepared by melt-spun techniques. Such pieces of ribbons were consolidated under the same conditions on Bridgman anvils using a pressure of 6 GPa at room
Two different methods were employed to prepare samples of the ternary intermetallic phase: AlNi 2... more Two different methods were employed to prepare samples of the ternary intermetallic phase: AlNi 2 Ti, and of Al 0.4 Fe 0.5 Ni 0.1 , Al 0.4 Fe 0.3 Ni 0.3 , Al 0.4 Fe 0.1 Ni 0.5 solid solutions, respectively. Alloys were then subjected to heat treatment for homogenization. Phase identification was made by XRD phase analysis and by the SEM BSE technique, and chemical composition was determined using the EDS method. Heat capacity measurements were made within a temperature range from 100 to 600 K using the DSC technique. Results were listed in tables and then fitted to a Kelley equation; an example of C p vs. T curve is given.
ABSTRACT Metallic glasses of the composition Ti40Zr10Cu40−xPd10+x with x = 0, 4 and 10, were inve... more ABSTRACT Metallic glasses of the composition Ti40Zr10Cu40−xPd10+x with x = 0, 4 and 10, were investigated from the point of view of the thermal stability, crystallization and hardness. The samples in the form of melt spun ribbons and rods 2.8 mm in diameter, were characterized by differential scanning calorimetry (DSC), Thermo-Mechanical Analysis (TMA), macro-Vickers hardness (MHv10) and depth-sensing indentation measurements. The TMA experiments were performed on ribbons in the modulated constant load tensile mode. The processes of relaxation, glass transition and crystallization were observed with DSC and transmission electron microscopy (TEM). The relative length changes rates as a function of temperature (dL/dTL0) showed influence of the thermal stability of the amorphous phase on the materials ductility. High ductility was available in the wide range of temperature including primary crystallization range. Vickers-macrohardness of BMG was about 5500 MPa and nanohardness was about 9300 MPa, increasing after crystallization completion by about 18%. At small nanoindentation rates deformed amorphous phase revealed local plastic instability resulting from the shear bands formation.
In the present work, the effect of a new type of tetra-needle-shaped zinc oxide whisker (T-ZnOw) ... more In the present work, the effect of a new type of tetra-needle-shaped zinc oxide whisker (T-ZnOw) on crystallization behavior and properties of high-density polyethylene (HDPE) has been intensively researched. Our results show that, although the interfacial interaction between HDPE and T-ZnOw is very weak, addition of T-ZnOw induces the increase of relative crystallinity and the decrease of lamellar thickness in composites. Mechanical test shows that T-ZnOw induces the gradual decline of impact toughness of composites due to the weak interaction between T-ZnOw and HDPE matrix. Based on the fractograph of composites, it has been deduced that during the impact process, the microvoid forms firstly in the interface of T-ZnOw/HDPE, and then propagates to the matrix, resulting in the formation of macrocrack and finally leading to the fracture of the sample. As expected, addition of T-ZnOw induces the gradual enhancement of the modulus of the composites with the increasing content of T-ZnOw.
In the present study we report the changes in the modified near-surface layer on NiTi shape memor... more In the present study we report the changes in the modified near-surface layer on NiTi shape memory alloy, caused by ion implantation as well as their influence on the structure and mechanical properties of this material. Experimental results of an inhomogeneous structure and tribological properties of implanted NiTi are discussed in this paper.
This paper reports the application of nitrogen ion implantation for modification of a shape memor... more This paper reports the application of nitrogen ion implantation for modification of a shape memory alloy. It is known that the problem of creating a protective surface coating for the shape memory alloy is the most acute for potential applications of this material. Thus, the problem of increasing surface protective properties and, at the same time, simultaneous preservation of functional properties of shape memory materials is a subject of research and development [Pelletier H, Muller D, Mille P, Grob J. Surf Coat Technol 2002;158:309.]. The surface characterization of nitrogen implanted (fluence 1018 cm_2 and energy 50 keV) equiatomic commercial NiTi alloy samples was performed with the assistance of high resolution transmission electron microscopy (HTEM) techniques and modifications of phase composition before and after irradiation are studied at room and martensitic transformation temperatures by X-ray diffraction methods. Differential scanning calorimetry (DSC, TA Instruments) was used to characterize the transformation sequence and transformation temperatures for the initial and surface-modified materials. Experimental results of an inhomogeneous structure of near-surface layers in the ionimplanted NiTi alloy are discussed in this paper.
In this work (Ti,Si,Al)N films were deposited using only rf or a combination of rf and d.c. react... more In this work (Ti,Si,Al)N films were deposited using only rf or a combination of rf and d.c. reactive magnetron sputtering. Chemical composition, thickness, film structure and mechanical properties of the films were investigated by means of Rutherford backscattering (RBS), electron microprobe analysis (EPMA), ball-cratering, X-ray diffraction (XRD) and ultramicroindentation, respectively. All samples showed high hardness values, exceeding, in some cases, 50 GPa. XRD results revealed the formation of a mixture of two phases whose structure is similar to TiN. One phase is noted as being TiN bulk with a lattice parameter of 0.428 nm and develops only in conditions of high surface mobility. This behaviour can be associated with the segregation of the SiN phase, though the formation of an amorphous AlN phase cannot be excluded. Another phase, which is noted as Ti-Si-Al-N x (af0.420 nm), where Si and Al atoms substitute the Ti atoms on the TiN lattice, develops in situations of lower surface mobility. The thermal stability of these coatings was studied by thermal treatments in a vacuum atmosphere, where it was found that a small increase in hardness was obtained after 1 h heat treatment at 8008C. ᮊ
Cold-consolidation using high pressure torsion (HPT) has been applied to ball-milled Fe-based amo... more Cold-consolidation using high pressure torsion (HPT) has been applied to ball-milled Fe-based amorphous ribbons to process bulk disks of approximately 9 mm in diameter and 0.3 mm in thickness. The mainly amorphous bulk samples demonstrated soft magnetic behavior, higher Curie temperature and enhanced microhardness with respect to the ribbons.
Transactions of Nonferrous Metals Society of China, 2010
A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to p... more A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to produce thixo-casts from steel. After inductive heating to the required semi-solid temperature range, the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die. Bearing steel 100Cr6 (after forging) was used as the feedstock material. The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 µm and 8 µm. Differential scanning calorimetry (DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 ˚C which was attributed to about 45% of a liquid phase. With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 µm to 40 µm. The microstructure of globules indicated predominant presence of martensite (about 76% volume fraction) with residual austenite between plates. X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite. The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60, which confirms the presence of martensite and carbides. The thixo-casts were subjected to low tempering, at temperature of 150 ˚C for a period of 2 h, in order to remove stresses created during the process of thixoforming and to increase plasticity. The hardness after tempering was HRC 62.3. Additionally, in order to identify phases present in the thixo-casts, transmission electron microscopy (TEM) was carried out.
This paper summarizes theoretical and experimental studies of cBN–Zr composites of cBN:Zr molar r... more This paper summarizes theoretical and experimental studies of cBN–Zr composites of cBN:Zr molar ratio equal 9:1. From theoretical calculations it follows that Zr reacts with cBN in the full range of pressure (1·3×10−3–1×107 Pa) for temperatures 950 and 1750°C to form at two new phases: ZrB2 and ZrN whose amount depends on the conditions of synthesis. Experimentally, composite based on cubic boron nitride (cBN) with zirconium addition used as a binding material was prepared by high pressure hot pressing. Samples before and after heat treatment were characterized using transmission electron microscope. The TEM showed that after sintering a thin zone of fine ZrB2 and ZrN crystallites was formed at the cBN/Zr interface. After additional heat treatment the ZrN crystallites grew forming a layer up to 2 mm thick built from columnar grains of 0·1–0·2 mm in diameter. The ZrB2 remained as a thin (0·1 to 0·2 μm) layer of very fine equiaxial crystallites between the ZrN and cBN. The hardness of such sintered material was 20 GPa/HK1, after additional heat treatment at 950°C for 1h in vacuum of 3×10−3 Pa the hardness increased up to 29 GPa/HK1.
Two Ni-Ti-Zr -based amorphous ribbons of compositions Ni 56 Cu 2 Zr 18 Ti 16 Al 3 Si 5 and Ni 36 ... more Two Ni-Ti-Zr -based amorphous ribbons of compositions Ni 56 Cu 2 Zr 18 Ti 16 Al 3 Si 5 and Ni 36 Cu 23 Zr 18 Ti 14 Al 5 Si 4 were prepared by melt-spun techniques. Such pieces of ribbons were consolidated under the same conditions on Bridgman anvils using a pressure of 6 GPa at room
Two different methods were employed to prepare samples of the ternary intermetallic phase: AlNi 2... more Two different methods were employed to prepare samples of the ternary intermetallic phase: AlNi 2 Ti, and of Al 0.4 Fe 0.5 Ni 0.1 , Al 0.4 Fe 0.3 Ni 0.3 , Al 0.4 Fe 0.1 Ni 0.5 solid solutions, respectively. Alloys were then subjected to heat treatment for homogenization. Phase identification was made by XRD phase analysis and by the SEM BSE technique, and chemical composition was determined using the EDS method. Heat capacity measurements were made within a temperature range from 100 to 600 K using the DSC technique. Results were listed in tables and then fitted to a Kelley equation; an example of C p vs. T curve is given.
ABSTRACT Metallic glasses of the composition Ti40Zr10Cu40−xPd10+x with x = 0, 4 and 10, were inve... more ABSTRACT Metallic glasses of the composition Ti40Zr10Cu40−xPd10+x with x = 0, 4 and 10, were investigated from the point of view of the thermal stability, crystallization and hardness. The samples in the form of melt spun ribbons and rods 2.8 mm in diameter, were characterized by differential scanning calorimetry (DSC), Thermo-Mechanical Analysis (TMA), macro-Vickers hardness (MHv10) and depth-sensing indentation measurements. The TMA experiments were performed on ribbons in the modulated constant load tensile mode. The processes of relaxation, glass transition and crystallization were observed with DSC and transmission electron microscopy (TEM). The relative length changes rates as a function of temperature (dL/dTL0) showed influence of the thermal stability of the amorphous phase on the materials ductility. High ductility was available in the wide range of temperature including primary crystallization range. Vickers-macrohardness of BMG was about 5500 MPa and nanohardness was about 9300 MPa, increasing after crystallization completion by about 18%. At small nanoindentation rates deformed amorphous phase revealed local plastic instability resulting from the shear bands formation.
In the present work, the effect of a new type of tetra-needle-shaped zinc oxide whisker (T-ZnOw) ... more In the present work, the effect of a new type of tetra-needle-shaped zinc oxide whisker (T-ZnOw) on crystallization behavior and properties of high-density polyethylene (HDPE) has been intensively researched. Our results show that, although the interfacial interaction between HDPE and T-ZnOw is very weak, addition of T-ZnOw induces the increase of relative crystallinity and the decrease of lamellar thickness in composites. Mechanical test shows that T-ZnOw induces the gradual decline of impact toughness of composites due to the weak interaction between T-ZnOw and HDPE matrix. Based on the fractograph of composites, it has been deduced that during the impact process, the microvoid forms firstly in the interface of T-ZnOw/HDPE, and then propagates to the matrix, resulting in the formation of macrocrack and finally leading to the fracture of the sample. As expected, addition of T-ZnOw induces the gradual enhancement of the modulus of the composites with the increasing content of T-ZnOw.
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