rus
Issue #1/2025
E.V.Gladkikh, G.Kh.Sultanova, A.A.Rusakov, A.S.Useinov, V.V.Molokanov, A.V.Krutilin, N.A.Palii
MECHANICAL PROPERTIES STUDY OF AMORPHOUS Co-ALLOY 84KHSR VARIABLE DIAMETER WIRE BY INSTRUMENTAL INDENTATION METHOD
MECHANICAL PROPERTIES STUDY OF AMORPHOUS Co-ALLOY 84KHSR VARIABLE DIAMETER WIRE BY INSTRUMENTAL INDENTATION METHOD
DOI: https://doi.org/10.22184/1993-8578.2025.18.1.30.38
The study of spatial distribution of mechanical properties in a "thick" amorphous wire of Co-alloy 84KHSR has been carried out. A cone sample of amorphous wire of variable diameter (70–300 μm) was obtained by the Ulitovsky-Taylor method by varying the drawing speed during the wire production process. After removing the glass sheath and checking for the conformity of the wire structure to the amorphous state, the mechanical properties of the cone wire samples with diameters of 100 and 270 μm were studied by the instrumental indentation method. It was found that amorphous wire in the range of diameters 70–300 μm retains stable values of hardness and modulus of elasticity in cross and longitudinal sections. Mechanical properties of wires of the studied diameters also practically do not change when moving from the center of the samples to the edge. The obtained data indicate high isotropy of the amorphous structure of the wire of variable diameter. The noted higher values of hardness and modulus of elasticity in the 270 µm diameter sample (Н = 9,8 GPa, Е = 212 GPa) compared to the 100 µm diameter sample (Н = 8,6 GPa, Е = 163 GPa) may be due to a more intensive formation of the cluster structure due to a decrease in the effective cooling rate of the "thicker" wire. It was noted that such wires may find application in the manufacture of new types of medical instruments.
The study of spatial distribution of mechanical properties in a "thick" amorphous wire of Co-alloy 84KHSR has been carried out. A cone sample of amorphous wire of variable diameter (70–300 μm) was obtained by the Ulitovsky-Taylor method by varying the drawing speed during the wire production process. After removing the glass sheath and checking for the conformity of the wire structure to the amorphous state, the mechanical properties of the cone wire samples with diameters of 100 and 270 μm were studied by the instrumental indentation method. It was found that amorphous wire in the range of diameters 70–300 μm retains stable values of hardness and modulus of elasticity in cross and longitudinal sections. Mechanical properties of wires of the studied diameters also practically do not change when moving from the center of the samples to the edge. The obtained data indicate high isotropy of the amorphous structure of the wire of variable diameter. The noted higher values of hardness and modulus of elasticity in the 270 µm diameter sample (Н = 9,8 GPa, Е = 212 GPa) compared to the 100 µm diameter sample (Н = 8,6 GPa, Е = 163 GPa) may be due to a more intensive formation of the cluster structure due to a decrease in the effective cooling rate of the "thicker" wire. It was noted that such wires may find application in the manufacture of new types of medical instruments.
Теги: elastic modulus hardness instrumented indentation microwires "thick" amorphous wire "толстый" аморфный провод инструментальное индентирование модуль упругости твердость
INTRODUCTION
Amorphous wires based on the Co-Fe-Cr-Si-B system have a unique complex of mechanical, magnetic, physical, and corrosion properties [1–5]. The Ulitovsky-Taylor method [6] used to produce wires in a glass sheath makes it possible to fix the amorphous state of the wire at extremely low drawing speeds due to adiabatic compression of the melt by the glass shell. When using cobalt-based alloys with high glass-forming ability, this method can produce long wires with amorphous structure and high mechanical properties in a wide range of diameters from 5 to 300 μm [7, 8]. Moreover, due to the controlled change of drawing speed it is possible to obtain amorphous wires with variable diameter along the length. Such a wire can be of great interest to prepare the new types of medical instruments for endovascular interventions: conductors, microspirals, and stents [4]. Amorphous wires of large diameters based on Co have high electrical resistance (1.2–1.4 · 10–6 Ohm-m), high tensile strength (2500–3000 MPa) combined with high bending pseudoplasticity. The high sensitivity of the electrical resistance of amorphous wires to applied loads (strain resistance coefficient K, equals 2) combining with high strength and corrosion resistance opens good prospects for the use of such amorphous wires as stress-sensitive elements of critical structures [8]. Practical interest has been noted in amorphous wires up to 70 μm in diameter used for the fabrication of extended strain gauges [9–12]. The possibility of fabricating magnetically soft amorphous microspirals of variable stiffness with diameters from 20 to 100 μm is of interest [4].
The mechanical properties of large diameter wires have not been systematically studied. In order to expand the potential application areas of a new group of "thick" amorphous wires by the method of instrumental indentation, stresses influence made by the glass shell and the adopted method of melt jet quenching on the level and character of mechanical properties distribution along the cross-section and length of a cone amorphous wire of the model 84KHSR alloy with a variable diameter of 100–300 μm was studied.
EXPERIMENTAL PROCEDURE
To prepare the microwires, a precursor was used – a rod billet obtained by zone melting, which excluded appearance of defects, internal pores and external sinks [13]. The cone wire sample of variable diameter was obtained by the Ulitovsky-Taylor method. A 4 mm diameter rod billet of 84KHSR Co-alloy was subjected to melting in a glass tube and joint drawing of the melt jet and softened glass on a rotating drum according to the mode ensuring the production of a continuous wire with a diameter of 70 µm with high technological properties. Then the drum rotation speed was sharply reduced to the value ensuring the process of obtaining a wire with a diameter of about 300 microns. The glass shell was mechanically removed from the obtained wire. For the purpose of research, the cone section of the wire obtained during the transition from a diameter of 70 μm to a diameter of 300 μm was cut off. From the obtained wire section, samples near diameters of 100 and 270 µm were cut off for research. The wire sections near the selected diameters successfully passed the technological test for ability to bend freely at 90 degrees without fracture. Analysis of the wire samples of two selected diameters, performed on a Setaram Setsys Evolution differential scanning calorimeter, showed presence of two characteristic combined exo-effect peaks corresponding to crystallisation of the amorphous phase. The test results confirmed compliance of the wire structure with the amorphous state over the entire range of wire diameters selected for the study of mechanical properties by the instrumental indentation method.
For instrumental indentation, slices of amorphous wire samples of two selected diameters were prepared in longitudinal and transverse directions. The samples were cast in epoxy washers and polished using Tegra Pol-11 grinding and polishing equipment (Stuers, Denmark).
Roughness of the samples was studied using a confocal 3D profilometer S Neox (Sensofar, Spain). The scanning field is 113 × 94 μm. A light source with a wavelength of 530 nm was used.
Hardness and modulus of elasticity of amorphous wire samples were studied by instrumental indentation method using NanoScan-4D nanohardness tester (Russia). Several series of measurements with a maximum load of 10 mN were carried out. An indenter with a diamond pyramid of Berkovich type was used [14].
RESULTS AND DISCUSSION
For nanohardness tests performed with low
load, a high-quality sample preparation is necessary. The indentation depth should be at least 20 times the surface roughness of the sample [14–16]. The experimentally achieved surface roughness (Ra) after polishing the samples was less than 10 nm. The obtained result confirmed possibility of tool indentation at an indentation depth of 200 nm and more.
A series of prints was obtained by moving the indenter along and across the longitudinal axis of the specimen. Five tracks each with a distance between the prints of 6 µm were applied to the transverse and longitudinal slits of the wire with a diameter of 270 µm. The value of the applied load was 10 mN. Each track consisted of 45 prints, however the outermost ones were discarded due to the close proximity of the fill material which would have affected the measured mechanical property values. The obtained values of hardness and elastic modulus corresponding to the same coordinate along the track were averaged. The results of dependence of average values of hardness and modulus of elasticity along the track coordinate are shown in Fig.1. It was found that, taking into account the standard deviation, the obtained values do not depend on the location of the hardness measurement location along the specimen surface for both vertical location of the wire in the casting and horizontal location. This indicates high homogeneity of mechanical properties of the 270 µm diameter amorphous wire sample.
In order to reveal homogeneity of mechanical properties of a wire with a diameter of 100 µm, the following experiment was carried out. A grid of indentations at 6 µm intervals was applied on the surface of the wire end slit (Fig.2a). The load was also 10 mN. The obtained hardness values and elastic modulus were presented as a function of the length of the radius vector drawn from the centre of the end face to the periphery. It was assumed that in case of heterogeneity of mechanical properties depending on the imprint location, the hardness values and modulus of elasticity in the centre and at the edges of the wire would be different. Since the slope coefficient of the straight lines drawn in the plots of hardness (Fig.2b) and modulus of elasticity (Fig.2c) dependence on the radius vector is less than 0.5% of the value of the free term, it can be concluded that the mechanical properties measured along the cross-section of the wire with a diameter of 100 µm are homogeneous. At the same time, the underestimated values of the elastic modulus at the edges of the specimen are related to the angle of inclination of the edge formed during polishing.
On a longitudinal wire sample with a diameter of 100 µm, a series of measurements similar to that used for the study of 270 µm thick wire samples, Fig.1a, was performed: 5 tracks with a footprint spacing of 6 µm and an applied load of 10 mN.
The resulting values of hardness and modulus of elasticity on 4 wire samples of 270 and 100 µm diameter obtained by averaging all measured values are shown in Fig.3. Within the error limits (standard deviation from the mean), the values of both hardness and modulus of elasticity coincide.
From the presented results, it is observed that the amorphous wire samples with diameters of 100 and 270 μm maintain stable values of hardness and modulus of elasticity in cross and longitudinal sections. Mechanical properties of wires of the studied diameters also practically do not change when moving from the centre of the samples to the edge. It was found that the 270 μm diameter sample has higher hardness and elastic modulus compared to the 100 μm diameter sample (Fig.3), which may be due to a more intensive process of cluster formation in the melt due to decreasing of the effective quenching rate of a thicker wire.
A series of measurements with loads of 1, 2, 5, 10, 20 and 50 mN were performed on a longitudinal slice of 100 µm diameter specimens. The modulus of elasticity decreased with increasing indentation depth; at low loads the measured values had a large scatter due to specimen roughness (at a load of 1 mN the indentation depth is about 100 nm). Therefore, we believe that the lower hardness values on these samples are due to the soft epoxy resin influence where the samples are cast.
CONCLUSIONS
Using the instrumental indentation method, influence of stresses performed by the glass shell and the adopted method of melt jet quenching on the level and character of distribution of mechanical properties in a conical amorphous wire of variable diameter of the model 84KKHSR alloy has been studied.
It was found that amorphous wire in the diameter range of 70–300 µm maintains stable values of hardness and elastic modulus in cross and longitudinal sections. The obtained data testify to the isotropy of wires of variable diameter with amorphous structure. Higher values of hardness and modulus of elasticity in the 270 μm diameter sample (H = 9.8 GPa, E = 212 GPa) compared to the 100 μm diameter sample (H = 8 GPa, E = 163 GPa) may be due to a more intensive process of cluster formation in the melt due to decreasing the effective quenching rate of the thicker wire.
It is shown that "thick" amorphous wires of 84KKHSR Co-alloy retain a high level of strength and elastic properties in a wide range of diameters. Such wires of variable diameter can be used in the manufacturing of new types of surgical instruments for endovascular interventions, and instruments for endodontic operations.
ACKNOWLEDGEMENTS
The study was carried out using the equipment of the Collective Use Centre of FGBNU TISNUM "Research of nanostructured, carbon and superhard materials". The authors express their gratitude to Petrzhik M.I. for attention to the work and valuable comments during the results discussion. The work was carried out within the framework of State Order No. 075-00320-24-00.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Amorphous wires based on the Co-Fe-Cr-Si-B system have a unique complex of mechanical, magnetic, physical, and corrosion properties [1–5]. The Ulitovsky-Taylor method [6] used to produce wires in a glass sheath makes it possible to fix the amorphous state of the wire at extremely low drawing speeds due to adiabatic compression of the melt by the glass shell. When using cobalt-based alloys with high glass-forming ability, this method can produce long wires with amorphous structure and high mechanical properties in a wide range of diameters from 5 to 300 μm [7, 8]. Moreover, due to the controlled change of drawing speed it is possible to obtain amorphous wires with variable diameter along the length. Such a wire can be of great interest to prepare the new types of medical instruments for endovascular interventions: conductors, microspirals, and stents [4]. Amorphous wires of large diameters based on Co have high electrical resistance (1.2–1.4 · 10–6 Ohm-m), high tensile strength (2500–3000 MPa) combined with high bending pseudoplasticity. The high sensitivity of the electrical resistance of amorphous wires to applied loads (strain resistance coefficient K, equals 2) combining with high strength and corrosion resistance opens good prospects for the use of such amorphous wires as stress-sensitive elements of critical structures [8]. Practical interest has been noted in amorphous wires up to 70 μm in diameter used for the fabrication of extended strain gauges [9–12]. The possibility of fabricating magnetically soft amorphous microspirals of variable stiffness with diameters from 20 to 100 μm is of interest [4].
The mechanical properties of large diameter wires have not been systematically studied. In order to expand the potential application areas of a new group of "thick" amorphous wires by the method of instrumental indentation, stresses influence made by the glass shell and the adopted method of melt jet quenching on the level and character of mechanical properties distribution along the cross-section and length of a cone amorphous wire of the model 84KHSR alloy with a variable diameter of 100–300 μm was studied.
EXPERIMENTAL PROCEDURE
To prepare the microwires, a precursor was used – a rod billet obtained by zone melting, which excluded appearance of defects, internal pores and external sinks [13]. The cone wire sample of variable diameter was obtained by the Ulitovsky-Taylor method. A 4 mm diameter rod billet of 84KHSR Co-alloy was subjected to melting in a glass tube and joint drawing of the melt jet and softened glass on a rotating drum according to the mode ensuring the production of a continuous wire with a diameter of 70 µm with high technological properties. Then the drum rotation speed was sharply reduced to the value ensuring the process of obtaining a wire with a diameter of about 300 microns. The glass shell was mechanically removed from the obtained wire. For the purpose of research, the cone section of the wire obtained during the transition from a diameter of 70 μm to a diameter of 300 μm was cut off. From the obtained wire section, samples near diameters of 100 and 270 µm were cut off for research. The wire sections near the selected diameters successfully passed the technological test for ability to bend freely at 90 degrees without fracture. Analysis of the wire samples of two selected diameters, performed on a Setaram Setsys Evolution differential scanning calorimeter, showed presence of two characteristic combined exo-effect peaks corresponding to crystallisation of the amorphous phase. The test results confirmed compliance of the wire structure with the amorphous state over the entire range of wire diameters selected for the study of mechanical properties by the instrumental indentation method.
For instrumental indentation, slices of amorphous wire samples of two selected diameters were prepared in longitudinal and transverse directions. The samples were cast in epoxy washers and polished using Tegra Pol-11 grinding and polishing equipment (Stuers, Denmark).
Roughness of the samples was studied using a confocal 3D profilometer S Neox (Sensofar, Spain). The scanning field is 113 × 94 μm. A light source with a wavelength of 530 nm was used.
Hardness and modulus of elasticity of amorphous wire samples were studied by instrumental indentation method using NanoScan-4D nanohardness tester (Russia). Several series of measurements with a maximum load of 10 mN were carried out. An indenter with a diamond pyramid of Berkovich type was used [14].
RESULTS AND DISCUSSION
For nanohardness tests performed with low
load, a high-quality sample preparation is necessary. The indentation depth should be at least 20 times the surface roughness of the sample [14–16]. The experimentally achieved surface roughness (Ra) after polishing the samples was less than 10 nm. The obtained result confirmed possibility of tool indentation at an indentation depth of 200 nm and more.
A series of prints was obtained by moving the indenter along and across the longitudinal axis of the specimen. Five tracks each with a distance between the prints of 6 µm were applied to the transverse and longitudinal slits of the wire with a diameter of 270 µm. The value of the applied load was 10 mN. Each track consisted of 45 prints, however the outermost ones were discarded due to the close proximity of the fill material which would have affected the measured mechanical property values. The obtained values of hardness and elastic modulus corresponding to the same coordinate along the track were averaged. The results of dependence of average values of hardness and modulus of elasticity along the track coordinate are shown in Fig.1. It was found that, taking into account the standard deviation, the obtained values do not depend on the location of the hardness measurement location along the specimen surface for both vertical location of the wire in the casting and horizontal location. This indicates high homogeneity of mechanical properties of the 270 µm diameter amorphous wire sample.
In order to reveal homogeneity of mechanical properties of a wire with a diameter of 100 µm, the following experiment was carried out. A grid of indentations at 6 µm intervals was applied on the surface of the wire end slit (Fig.2a). The load was also 10 mN. The obtained hardness values and elastic modulus were presented as a function of the length of the radius vector drawn from the centre of the end face to the periphery. It was assumed that in case of heterogeneity of mechanical properties depending on the imprint location, the hardness values and modulus of elasticity in the centre and at the edges of the wire would be different. Since the slope coefficient of the straight lines drawn in the plots of hardness (Fig.2b) and modulus of elasticity (Fig.2c) dependence on the radius vector is less than 0.5% of the value of the free term, it can be concluded that the mechanical properties measured along the cross-section of the wire with a diameter of 100 µm are homogeneous. At the same time, the underestimated values of the elastic modulus at the edges of the specimen are related to the angle of inclination of the edge formed during polishing.
On a longitudinal wire sample with a diameter of 100 µm, a series of measurements similar to that used for the study of 270 µm thick wire samples, Fig.1a, was performed: 5 tracks with a footprint spacing of 6 µm and an applied load of 10 mN.
The resulting values of hardness and modulus of elasticity on 4 wire samples of 270 and 100 µm diameter obtained by averaging all measured values are shown in Fig.3. Within the error limits (standard deviation from the mean), the values of both hardness and modulus of elasticity coincide.
From the presented results, it is observed that the amorphous wire samples with diameters of 100 and 270 μm maintain stable values of hardness and modulus of elasticity in cross and longitudinal sections. Mechanical properties of wires of the studied diameters also practically do not change when moving from the centre of the samples to the edge. It was found that the 270 μm diameter sample has higher hardness and elastic modulus compared to the 100 μm diameter sample (Fig.3), which may be due to a more intensive process of cluster formation in the melt due to decreasing of the effective quenching rate of a thicker wire.
A series of measurements with loads of 1, 2, 5, 10, 20 and 50 mN were performed on a longitudinal slice of 100 µm diameter specimens. The modulus of elasticity decreased with increasing indentation depth; at low loads the measured values had a large scatter due to specimen roughness (at a load of 1 mN the indentation depth is about 100 nm). Therefore, we believe that the lower hardness values on these samples are due to the soft epoxy resin influence where the samples are cast.
CONCLUSIONS
Using the instrumental indentation method, influence of stresses performed by the glass shell and the adopted method of melt jet quenching on the level and character of distribution of mechanical properties in a conical amorphous wire of variable diameter of the model 84KKHSR alloy has been studied.
It was found that amorphous wire in the diameter range of 70–300 µm maintains stable values of hardness and elastic modulus in cross and longitudinal sections. The obtained data testify to the isotropy of wires of variable diameter with amorphous structure. Higher values of hardness and modulus of elasticity in the 270 μm diameter sample (H = 9.8 GPa, E = 212 GPa) compared to the 100 μm diameter sample (H = 8 GPa, E = 163 GPa) may be due to a more intensive process of cluster formation in the melt due to decreasing the effective quenching rate of the thicker wire.
It is shown that "thick" amorphous wires of 84KKHSR Co-alloy retain a high level of strength and elastic properties in a wide range of diameters. Such wires of variable diameter can be used in the manufacturing of new types of surgical instruments for endovascular interventions, and instruments for endodontic operations.
ACKNOWLEDGEMENTS
The study was carried out using the equipment of the Collective Use Centre of FGBNU TISNUM "Research of nanostructured, carbon and superhard materials". The authors express their gratitude to Petrzhik M.I. for attention to the work and valuable comments during the results discussion. The work was carried out within the framework of State Order No. 075-00320-24-00.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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