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.
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.
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.
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.
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.
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.
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