Pub Date : 2021-09-17DOI: 10.17073/1997-308x-2021-3-22-33
V. Dorofeyev, A. Sviridova, V. Samoilov
One of the main problems limiting further growth in the production of parts by the hot forging of porous performs (HFPP) is that the obtained materials are prone to brittle fracture due to the poor quality of interparticle jointing formed during hot deformation, as well as the presence of impurities in the composition of initial powders. The paper studies the possibility of increasing the mechanical properties and endurance performance of hot-deformed powder steels by doping them with sodium or calcium microadditives and using thermomechanical treatment. Sodium bicarbonate and calcium carbonate were used for microalloying. Carbon was added as pencil graphite powder. The temperature of heating porous preforms before hot forging and the carbon content in steels were varied; the content of microalloying additives was, wt.%: 0.2 for sodium, and 0.3 for calcium. Mechanical properties as well as contact and low-cycle fatigue life were tested on 5 × 10 × 55 mm and 10 × 10 × 55 mm prismatic specimens, as well as ∅ 26 × 6 mm cylindrical specimens. In comparison with carburizing and thermal treatment, thermomechanical treatment improves the impact strength and endurance performance of hot-deformed powder steels with Na or Ca microadditives under the contact and low-cycle fatigue loading, and the hot repressing temperature of porous preforms is reduced without compromising the mechanical properties of powder steels obtained. It may be associated with the formation of a more fine-grained structure and higher microstresses of the crystal lattice. The cooling down of preform surface layers during hot forging process operations creates conditions for ausforming in them.
{"title":"Formation of structure and properties of hot-deformed powder steels microalloyed with sodium and calcium during thermal and thermomechanical treatment","authors":"V. Dorofeyev, A. Sviridova, V. Samoilov","doi":"10.17073/1997-308x-2021-3-22-33","DOIUrl":"https://doi.org/10.17073/1997-308x-2021-3-22-33","url":null,"abstract":"One of the main problems limiting further growth in the production of parts by the hot forging of porous performs (HFPP) is that the obtained materials are prone to brittle fracture due to the poor quality of interparticle jointing formed during hot deformation, as well as the presence of impurities in the composition of initial powders. The paper studies the possibility of increasing the mechanical properties and endurance performance of hot-deformed powder steels by doping them with sodium or calcium microadditives and using thermomechanical treatment. Sodium bicarbonate and calcium carbonate were used for microalloying. Carbon was added as pencil graphite powder. The temperature of heating porous preforms before hot forging and the carbon content in steels were varied; the content of microalloying additives was, wt.%: 0.2 for sodium, and 0.3 for calcium. Mechanical properties as well as contact and low-cycle fatigue life were tested on 5 × 10 × 55 mm and 10 × 10 × 55 mm prismatic specimens, as well as ∅ 26 × 6 mm cylindrical specimens. In comparison with carburizing and thermal treatment, thermomechanical treatment improves the impact strength and endurance performance of hot-deformed powder steels with Na or Ca microadditives under the contact and low-cycle fatigue loading, and the hot repressing temperature of porous preforms is reduced without compromising the mechanical properties of powder steels obtained. It may be associated with the formation of a more fine-grained structure and higher microstresses of the crystal lattice. The cooling down of preform surface layers during hot forging process operations creates conditions for ausforming in them.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88102589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-15DOI: 10.17073/1997-308x-2020-4-22-32
S. Karpov, L. S. Stel'makh, A. Stolin
The paper presents a theoretical analysis of the single action pressing of powder materials featuring plasticity and compressibility. It takes into account dry external friction between the die material and side walls, which determines the strong nonlinearity of the problem considered. This problem has a number of features that complicate its numerical solution: the presence of external friction, the elastic-plastic law of material behavior description, as well as the calculation of large displacements and, as a consequence, strong geometric nonlinearity. To consider these features, a combination of Fleck–Kuhn–McMeeking and Gurson– Tvergaard–Needleman models was used to consider a wide range of changes in the porosity of materials. The numerical solution of the problem was carried out using finite element analysis with isoparametric elements. The increment of plastic deformations at each step was determined from nonlinear equations of plastic flow. Stresses at the Gaussian points were updated according to the specified increments of deformations to calculate the material behavior during deformation. Unknown density and strain values as functions of coordinate and time were calculated. The influence of the different height-to-diameter ratio of the blank and the value of external friction of the material stress-strain state and compaction kinetics were considered. The distribution of equivalent stresses and the value of volumetric plastic deformations in the material, as well as the nonuniformity of relative density at the end of the pressing period were studied. The theoretical analysis made it possible to study the basic compaction kinetics laws for powder materials with nonuniform density under conditions of dry friction on side walls. The results obtained are relevant for predicting possible negative changes in the blank geometry when implementing the single action pressing scheme for powder materials.
{"title":"Mathematical modeling of single action pressing of powder materials under dry friction conditions","authors":"S. Karpov, L. S. Stel'makh, A. Stolin","doi":"10.17073/1997-308x-2020-4-22-32","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-4-22-32","url":null,"abstract":"The paper presents a theoretical analysis of the single action pressing of powder materials featuring plasticity and compressibility. It takes into account dry external friction between the die material and side walls, which determines the strong nonlinearity of the problem considered. This problem has a number of features that complicate its numerical solution: the presence of external friction, the elastic-plastic law of material behavior description, as well as the calculation of large displacements and, as a consequence, strong geometric nonlinearity. To consider these features, a combination of Fleck–Kuhn–McMeeking and Gurson– Tvergaard–Needleman models was used to consider a wide range of changes in the porosity of materials. The numerical solution of the problem was carried out using finite element analysis with isoparametric elements. The increment of plastic deformations at each step was determined from nonlinear equations of plastic flow. Stresses at the Gaussian points were updated according to the specified increments of deformations to calculate the material behavior during deformation. Unknown density and strain values as functions of coordinate and time were calculated. The influence of the different height-to-diameter ratio of the blank and the value of external friction of the material stress-strain state and compaction kinetics were considered. The distribution of equivalent stresses and the value of volumetric plastic deformations in the material, as well as the nonuniformity of relative density at the end of the pressing period were studied. The theoretical analysis made it possible to study the basic compaction kinetics laws for powder materials with nonuniform density under conditions of dry friction on side walls. The results obtained are relevant for predicting possible negative changes in the blank geometry when implementing the single action pressing scheme for powder materials.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80713340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-15DOI: 10.17073/1997-308x-2020-4-66-75
D. Ivanov, S. D. Shlyapin, G. Valiano
Alumo-matrix dispersion-hardened composite materials are widely used in engineering due to the combination of high strength and low density, allowing the production of lightweight endurable structural elements for various purposes. They are used for manufacturing abrasive, triboengineering products, parts of the internal combustion engine cylinder-piston group, airframe and other special products. The paper is aimed to study the fracture mechanism of a layered dispersion-hardened Al–Al2O3–Al4C3 composite on static loading and impact. Specimens were obtained by liquid phase sintering of PAP-2 powder blanks in a vacuum. The liquid phase was formed due to Al–Al4C3 eutectic melt. The layered structure appeared due to the liquid-phase splicing of PAP-2 scaly particles along the contacting planes. Dispersion hardening of aluminum matrix was achieved due to nanosized lamellar alumocarbide crystals precipitated from the eutectic melt on cooling. The synthesis of alumina crystals – δ-Al2O3 – occurred due to the interaction of aluminum with residual oxygen molecules of the air on sintering at the furnace rarefaction of 10–5 mm Hg. The stable destruction of samples by the «shear stratification» mechanism was found to occur under static loading accompanied by the formation of cavities due to tearing of layered blocks under the action of shear stresses (σb = 430÷500 MPa, K1s = 14.0÷ ÷15.5 MPa·m1/2) At shock loading, a significant amount of material is involved in the fracture accompanied by the formation of cleavage steps between layered blocks and extended regions of ductile fracture dimples. Thanks to this mechanism, a high KCU (1.1·105 J/m2) is achieved comparable with that of the VT-5L titanium alloy. The developed composite can be used for manufacturing lightweight structural elements operated under dynamic loading.
{"title":"Mechanism of destruction of the Al–Al4C3–Al2O3 alumo-matrix dispersion-hardened composite material with a layered structure on static and shock loading","authors":"D. Ivanov, S. D. Shlyapin, G. Valiano","doi":"10.17073/1997-308x-2020-4-66-75","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-4-66-75","url":null,"abstract":"Alumo-matrix dispersion-hardened composite materials are widely used in engineering due to the combination of high strength and low density, allowing the production of lightweight endurable structural elements for various purposes. They are used for manufacturing abrasive, triboengineering products, parts of the internal combustion engine cylinder-piston group, airframe and other special products. The paper is aimed to study the fracture mechanism of a layered dispersion-hardened Al–Al2O3–Al4C3 composite on static loading and impact. Specimens were obtained by liquid phase sintering of PAP-2 powder blanks in a vacuum. The liquid phase was formed due to Al–Al4C3 eutectic melt. The layered structure appeared due to the liquid-phase splicing of PAP-2 scaly particles along the contacting planes. Dispersion hardening of aluminum matrix was achieved due to nanosized lamellar alumocarbide crystals precipitated from the eutectic melt on cooling. The synthesis of alumina crystals – δ-Al2O3 – occurred due to the interaction of aluminum with residual oxygen molecules of the air on sintering at the furnace rarefaction of 10–5 mm Hg. The stable destruction of samples by the «shear stratification» mechanism was found to occur under static loading accompanied by the formation of cavities due to tearing of layered blocks under the action of shear stresses (σb = 430÷500 MPa, K1s = 14.0÷ ÷15.5 MPa·m1/2) At shock loading, a significant amount of material is involved in the fracture accompanied by the formation of cleavage steps between layered blocks and extended regions of ductile fracture dimples. Thanks to this mechanism, a high KCU (1.1·105 J/m2) is achieved comparable with that of the VT-5L titanium alloy. The developed composite can be used for manufacturing lightweight structural elements operated under dynamic loading.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83526966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-15DOI: 10.17073/1997-308x-2020-4-14-21
S. Vadchenko, E. Suvorova, N. I. Mukhina, I. Kovalev, E. V. Illarionova
: CuCr composite particles were obtained using the method of copper deposition from the solution of its sulfate onto chromium powder particles with the simultaneous mechanical activation (MA) of the mixture in an AGO-2 planetary ball mill for Powder Metallurgy and Functional Coatings 4 2020 5 minutes. CuSO 4 ·5H 2 O concentration in the solution with complete copper reduction provided a molar ratio of Cu/Cr = 1. Since deposited fine crystalline copper is highly active and rapidly oxidizes to Cu 2 O oxide in air, the obtained composite powders were washed, dried, and stored in an argon atmosphere. After drying, the mixture was subjected to additional MA for 5 minutes. Composite particles with a laminate structure begin to form in the solution during MA. Tablets were pressed with a diameter of 3 mm, height of up to 1.5 mm, and density of 4.2–4.5 g/cm 3 from the powders obtained. Samples were sintered in an argon atmosphere at 700– 1400 °С. For comparison of microstructures, samples were also sintered from mixtures of Cr and Cu metal powders with a volume ratio of chromium to copper of 50 : 50 obtained by simple mixing in a porcelain mortar for 20 minutes and MA for 10 minutes. Three areas of the alloy structure formation can be distinguished depending on the heating temperature. At heating temperatures below the eutectic melting point, composite particles are sintered at certain points. At heating temperatures above the liquidus temperature, the alloy melts with its phases separated; one part of the sample consists of copper enriched in chromium, and the other part consists of chromium enriched in copper. At intermediate heating temperatures, liquid phase sintering occurs accompanied by phase separation. Copper-enriched chromium particles become spherical and are located in a chromium-enriched copper matrix. Comparison of samples sintered under the same conditions from powder mixtures obtained by different methods showed that a more uniform and fine-grained structure is obtained in samples with deposited copper.
{"title":"Preparation of CuCr pseudo-alloys by deposition of copper from a solution onto chromium powders with simultaneous mechanical activation of the mixture","authors":"S. Vadchenko, E. Suvorova, N. I. Mukhina, I. Kovalev, E. V. Illarionova","doi":"10.17073/1997-308x-2020-4-14-21","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-4-14-21","url":null,"abstract":": CuCr composite particles were obtained using the method of copper deposition from the solution of its sulfate onto chromium powder particles with the simultaneous mechanical activation (MA) of the mixture in an AGO-2 planetary ball mill for Powder Metallurgy and Functional Coatings 4 2020 5 minutes. CuSO 4 ·5H 2 O concentration in the solution with complete copper reduction provided a molar ratio of Cu/Cr = 1. Since deposited fine crystalline copper is highly active and rapidly oxidizes to Cu 2 O oxide in air, the obtained composite powders were washed, dried, and stored in an argon atmosphere. After drying, the mixture was subjected to additional MA for 5 minutes. Composite particles with a laminate structure begin to form in the solution during MA. Tablets were pressed with a diameter of 3 mm, height of up to 1.5 mm, and density of 4.2–4.5 g/cm 3 from the powders obtained. Samples were sintered in an argon atmosphere at 700– 1400 °С. For comparison of microstructures, samples were also sintered from mixtures of Cr and Cu metal powders with a volume ratio of chromium to copper of 50 : 50 obtained by simple mixing in a porcelain mortar for 20 minutes and MA for 10 minutes. Three areas of the alloy structure formation can be distinguished depending on the heating temperature. At heating temperatures below the eutectic melting point, composite particles are sintered at certain points. At heating temperatures above the liquidus temperature, the alloy melts with its phases separated; one part of the sample consists of copper enriched in chromium, and the other part consists of chromium enriched in copper. At intermediate heating temperatures, liquid phase sintering occurs accompanied by phase separation. Copper-enriched chromium particles become spherical and are located in a chromium-enriched copper matrix. Comparison of samples sintered under the same conditions from powder mixtures obtained by different methods showed that a more uniform and fine-grained structure is obtained in samples with deposited copper.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"230 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89217290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-15DOI: 10.17073/1997-308x-2020-4-76-84
I. Evdokimov, R. R. Khayrullin, R. Bagramov, S. Perfilov, A. Pozdnyakov, V. Aksenenkov, B. Kulnitskiy
This paper is intended to continue the studies of magnesium effects on the structural phase composition, physical and mechanical properties of the nanostructured strain-hardened aluminum-magnesium alloys modified with C60 fullerene [1]. Previously obtained mechanically alloyed composite powders [1] were consolidated by direct hot extrusion method. Consolidation parameters were chosen based on previous studies of the structure and phase composition formation during mechanical alloying and heat treatment. It was found that an increase in magnesium concentration improves mechanical properties of extruded nanosructured composite materials, and additives modified by C60 fullerene stabilize the grain structure and slow down decomposition of α solid solution of magnesium in aluminum to 300 °C. Under similar thermobaric treatment Al82Mg18 (AMg18) not modified with C60 demonstrates a reduced α solid solution lattice constant and an increased average crystallite size. These processes are accompanied by sequential formation of γ, β′, and β phases, while γ and β′ are intermediate phases. The grain structure of extruded samples is typical for materials obtained in this way – grains are closely packed, elongated and oriented along the extrusion axis. The grain structure of extruded samples inherits the morphology of mechanically alloyed powders. Thus, mechanical alloying methods followed by intense plastic deformation (extrusion) improved mechanical properties significantly. Materials with ultimate tensile strength of 880 MPa; ultimate bending strength of 1100 MPa; microhardness up to 3300 MPa; and with the same density of 2.4–2.6 g/cm3 were obtained. This result demonstrates the prospects for using powder metallurgy techniques in the production of new nanostructured composite materials modified by C60 fullerene with improved physical and mechanical properties.
{"title":"Nanostructured strain-hardened aluminum-magnesium alloys modified by C60 fullerene obtained by powder metallurgy Part 2. The effect of magnesium concentration on physical and mechanical properties","authors":"I. Evdokimov, R. R. Khayrullin, R. Bagramov, S. Perfilov, A. Pozdnyakov, V. Aksenenkov, B. Kulnitskiy","doi":"10.17073/1997-308x-2020-4-76-84","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-4-76-84","url":null,"abstract":"This paper is intended to continue the studies of magnesium effects on the structural phase composition, physical and mechanical properties of the nanostructured strain-hardened aluminum-magnesium alloys modified with C60 fullerene [1]. Previously obtained mechanically alloyed composite powders [1] were consolidated by direct hot extrusion method. Consolidation parameters were chosen based on previous studies of the structure and phase composition formation during mechanical alloying and heat treatment. It was found that an increase in magnesium concentration improves mechanical properties of extruded nanosructured composite materials, and additives modified by C60 fullerene stabilize the grain structure and slow down decomposition of α solid solution of magnesium in aluminum to 300 °C. Under similar thermobaric treatment Al82Mg18 (AMg18) not modified with C60 demonstrates a reduced α solid solution lattice constant and an increased average crystallite size. These processes are accompanied by sequential formation of γ, β′, and β phases, while γ and β′ are intermediate phases. The grain structure of extruded samples is typical for materials obtained in this way – grains are closely packed, elongated and oriented along the extrusion axis. The grain structure of extruded samples inherits the morphology of mechanically alloyed powders. Thus, mechanical alloying methods followed by intense plastic deformation (extrusion) improved mechanical properties significantly. Materials with ultimate tensile strength of 880 MPa; ultimate bending strength of 1100 MPa; microhardness up to 3300 MPa; and with the same density of 2.4–2.6 g/cm3 were obtained. This result demonstrates the prospects for using powder metallurgy techniques in the production of new nanostructured composite materials modified by C60 fullerene with improved physical and mechanical properties.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88595822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-16DOI: 10.17073/1997-308x-2020-3-25-33
A. Revutsky, V. Y. Syrnev, V. Lopatin, O. Semilutskaya, T. Segeda
The paper presents the results of studying the effect of the state of grain boundaries (formed in the consolidation of beryllium powders by vacuum hot pressing on the strength properties of sintered beryllium. Scanning electron microscopy and X-ray spectral microanalysis were used to study the dependences of the morphology, elemental composition and structure of a dispersion hardening phase - beryllium oxide – on the content of low-melting impurities at the grain boundaries of sintered beryllium. A new hypothesis is proposed to explain the difference in the morphology and structure of reinforcing particles based on the transition features of amorphous beryllium oxide to a crystalline state (devitrification) at the grain boundaries of metallic beryllium. It is theoretically substantiated and experimentally confirmed that the devitrification mechanism can be homogeneous or heterogeneous depending on the content and ratio of silicon and aluminum impurities. This difference leads to the formation of either finely dispersed high-strength reinforcing particles of beryllium oxide or large, lower-strength oxide clusters. Changes in the morphology and structure of reinforcing oxide particles at the metallic beryllium grain boundaries, in its turn, influence the dynamics of beryllium microstructure grain growth during vacuum hot forming and, ultimately, the effect of dispersed grain-boundary hardening of sintered n beryllium. The paper provides the statistically processed results of testing the mechanical properties of industrial hot-pressed blanks produced of less than 56 μm powders to determine the effect of various factors (the content of impurities, their ratio and particle size of the initial powders) on the strength properties of hot-pressed beryllium. The adequacy of the obtained regularities was evaluated using the approximation confidence coefficients and confirmed the conclusions made in the theoretical and experimental analysis of the research problem. The statistical studies substantiated a comprehensive quality indicator of initial powders in order to predict the strength properties of hot-pressed beryllium. The results obtained substantiate new possibilities for controlling the mechanical properties of sintered beryllium for various purposes.
{"title":"Research of reinforcement phase formation on the borders of sintered berillium grains","authors":"A. Revutsky, V. Y. Syrnev, V. Lopatin, O. Semilutskaya, T. Segeda","doi":"10.17073/1997-308x-2020-3-25-33","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-3-25-33","url":null,"abstract":"The paper presents the results of studying the effect of the state of grain boundaries (formed in the consolidation of beryllium powders by vacuum hot pressing on the strength properties of sintered beryllium. Scanning electron microscopy and X-ray spectral microanalysis were used to study the dependences of the morphology, elemental composition and structure of a dispersion hardening phase - beryllium oxide – on the content of low-melting impurities at the grain boundaries of sintered beryllium. A new hypothesis is proposed to explain the difference in the morphology and structure of reinforcing particles based on the transition features of amorphous beryllium oxide to a crystalline state (devitrification) at the grain boundaries of metallic beryllium. It is theoretically substantiated and experimentally confirmed that the devitrification mechanism can be homogeneous or heterogeneous depending on the content and ratio of silicon and aluminum impurities. This difference leads to the formation of either finely dispersed high-strength reinforcing particles of beryllium oxide or large, lower-strength oxide clusters. Changes in the morphology and structure of reinforcing oxide particles at the metallic beryllium grain boundaries, in its turn, influence the dynamics of beryllium microstructure grain growth during vacuum hot forming and, ultimately, the effect of dispersed grain-boundary hardening of sintered n beryllium. The paper provides the statistically processed results of testing the mechanical properties of industrial hot-pressed blanks produced of less than 56 μm powders to determine the effect of various factors (the content of impurities, their ratio and particle size of the initial powders) on the strength properties of hot-pressed beryllium. The adequacy of the obtained regularities was evaluated using the approximation confidence coefficients and confirmed the conclusions made in the theoretical and experimental analysis of the research problem. The statistical studies substantiated a comprehensive quality indicator of initial powders in order to predict the strength properties of hot-pressed beryllium. The results obtained substantiate new possibilities for controlling the mechanical properties of sintered beryllium for various purposes.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75794595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-16DOI: 10.17073/1997-308x-2020-3-17-24
G. Bagliuk, S. Kyryliuk
The paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the deformable blank by means of internal cohesion in the die-material system. The study covers the evolution of relative density distribution over the blank cross section at different stages of deformation, stress-strain state and total strain force while varying the loading boundary conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that active friction forces acting on the periphery of the forging adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. At the same time, the volume of the high deformation intensity area and maximum values of deformation increase with a decrease in the spring initial compression force and, accordingly, with an increase in the die displacement value during deformation. Automatic die displacement due to internal cohesion in the die-deformable material system leads to a decrease in the total deformation force, and with a decrease in the die displacement value during deformation, the deformation force increases.
{"title":"Numerical analysis of porous blank die forging in the die with the implementation of active friction forces","authors":"G. Bagliuk, S. Kyryliuk","doi":"10.17073/1997-308x-2020-3-17-24","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-3-17-24","url":null,"abstract":"The paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the deformable blank by means of internal cohesion in the die-material system. The study covers the evolution of relative density distribution over the blank cross section at different stages of deformation, stress-strain state and total strain force while varying the loading boundary conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that active friction forces acting on the periphery of the forging adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. At the same time, the volume of the high deformation intensity area and maximum values of deformation increase with a decrease in the spring initial compression force and, accordingly, with an increase in the die displacement value during deformation. Automatic die displacement due to internal cohesion in the die-deformable material system leads to a decrease in the total deformation force, and with a decrease in the die displacement value during deformation, the deformation force increases.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"2016 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72745995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-16DOI: 10.17073/1997-308x-2020-3-4-16
M. Dvornik, E. Mikhailenko
The study covers the possibility of WC-15Co ultrafine cemented carbide production from powder obtained by spark erosion (SE) of VK15 cemented carbide waste in water. As a result of SE in an oxygen-containing liquid (H2O), the carbon content in the resulting powder decreases from 5.3 to 2.3 %. When the powder is heated to 900 °C in vacuum, the carbon content decreases to 0.2 % due to the presence of oxygen. The powder obtained consists of WC, W2C and Co phases. Particles have a dendritic structure consisting of newly formed tungsten-containing grains and cobalt interlayers. The controlled removal of oxygen and carbon replenishment in the resulting powder were carried out by heating in the CO atmosphere to t = = 900 °C. The processed powder has a required phase composition (WC + Co) and carbon content (5.3 %). Particles retain their spherical shape after carbon replenishment. WC grains in particles become plate-shaped with the space between them filled with cobalt. The average grain diameter is smaller than in the initial alloy. The vacuum sintering of the resulting powder at 1390 °C made it possible to obtain WC–15Co ultrafine-grained cemented carbide with an average WC grain diameter of 0.44 μm. It is several times smaller than the average grain diameter in the initial alloy (1.8 μm). Most grains retain their plate shape. The resulting alloy combines high hardness (1620 HV), increased fracture toughness (13.2 MPa·m1/2) and strength (1920 MPa) due to its fine-grain structure and 15 % cobalt content. In terms of the set of its properties, this alloy is not inferior to analogues obtained by other methods.
{"title":"Production of WC-15Co ultrafine-grained hard alloy from powder obtained by VK15 alloy waste spark erosion in water","authors":"M. Dvornik, E. Mikhailenko","doi":"10.17073/1997-308x-2020-3-4-16","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-3-4-16","url":null,"abstract":"The study covers the possibility of WC-15Co ultrafine cemented carbide production from powder obtained by spark erosion (SE) of VK15 cemented carbide waste in water. As a result of SE in an oxygen-containing liquid (H2O), the carbon content in the resulting powder decreases from 5.3 to 2.3 %. When the powder is heated to 900 °C in vacuum, the carbon content decreases to 0.2 % due to the presence of oxygen. The powder obtained consists of WC, W2C and Co phases. Particles have a dendritic structure consisting of newly formed tungsten-containing grains and cobalt interlayers. The controlled removal of oxygen and carbon replenishment in the resulting powder were carried out by heating in the CO atmosphere to t = = 900 °C. The processed powder has a required phase composition (WC + Co) and carbon content (5.3 %). Particles retain their spherical shape after carbon replenishment. WC grains in particles become plate-shaped with the space between them filled with cobalt. The average grain diameter is smaller than in the initial alloy. The vacuum sintering of the resulting powder at 1390 °C made it possible to obtain WC–15Co ultrafine-grained cemented carbide with an average WC grain diameter of 0.44 μm. It is several times smaller than the average grain diameter in the initial alloy (1.8 μm). Most grains retain their plate shape. The resulting alloy combines high hardness (1620 HV), increased fracture toughness (13.2 MPa·m1/2) and strength (1920 MPa) due to its fine-grain structure and 15 % cobalt content. In terms of the set of its properties, this alloy is not inferior to analogues obtained by other methods.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88797055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-16DOI: 10.17073/1997-308x-2020-3-34-40
T. Akopdzhanyan, E. A. Chemagina, P. BorovinskayaInna
The synthesis and sintering of the (AlN)x(SiC)1–x solid solution were studied under the conditions of SHS gasostatiс processing at high nitrogen gas pressures (up to 110 MPa). Phase formation during the combustion of aluminum and silicon carbide mixtures with the different amount of a combustible component (aluminum content is 35 to 60 wt.%) was studied. It was shown that the optimal amount of aluminum mixed with silicon carbide to obtain a single-phase solid solution (with the complete Al conversion to AlN and without SiC dissociation) is 45–50 wt.%. A mixture with 55–60 wt.% Al leads to excessively high temperatures, which in turn leads to the silicon carbide decomposition to Si + C elements. The optimal parameters for obtaining a dense material in one stage were determined. The measured porosity and density of materials obtained demonstrated that preforming is essential for the final density of samples containing 50 wt.% Al: maximum density was achieved at a preforming pressure of 10 MPa. It was found that the 5 wt.% yttrium oxide additive increases the material density by almost 10 %. A similar effect is also obtained by increasing the initial gas pressure from 80 to 110 MPa. The maximum density in this case reached 2.7 g/cm3, i.e. 83 % of the theoretical density. The total volumetric shrinkage of the material was 10 ± 0.5 %, and this indicator can be almost completely smoothed over by the 3 wt.% boron additive. The microhardness of samples was 2000 kg/mm2.
{"title":"Study into the feasibility of obtaining dense materials based on AlN-SiC solid solution in one stage by SHS gasostatiс processing","authors":"T. Akopdzhanyan, E. A. Chemagina, P. BorovinskayaInna","doi":"10.17073/1997-308x-2020-3-34-40","DOIUrl":"https://doi.org/10.17073/1997-308x-2020-3-34-40","url":null,"abstract":"The synthesis and sintering of the (AlN)x(SiC)1–x solid solution were studied under the conditions of SHS gasostatiс processing at high nitrogen gas pressures (up to 110 MPa). Phase formation during the combustion of aluminum and silicon carbide mixtures with the different amount of a combustible component (aluminum content is 35 to 60 wt.%) was studied. It was shown that the optimal amount of aluminum mixed with silicon carbide to obtain a single-phase solid solution (with the complete Al conversion to AlN and without SiC dissociation) is 45–50 wt.%. A mixture with 55–60 wt.% Al leads to excessively high temperatures, which in turn leads to the silicon carbide decomposition to Si + C elements. The optimal parameters for obtaining a dense material in one stage were determined. The measured porosity and density of materials obtained demonstrated that preforming is essential for the final density of samples containing 50 wt.% Al: maximum density was achieved at a preforming pressure of 10 MPa. It was found that the 5 wt.% yttrium oxide additive increases the material density by almost 10 %. A similar effect is also obtained by increasing the initial gas pressure from 80 to 110 MPa. The maximum density in this case reached 2.7 g/cm3, i.e. 83 % of the theoretical density. The total volumetric shrinkage of the material was 10 ± 0.5 %, and this indicator can be almost completely smoothed over by the 3 wt.% boron additive. The microhardness of samples was 2000 kg/mm2.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85150858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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