Search2022 Vol. 29, No. 6
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2022, vol. 29, no. 6, pp.
1133-1149.
https://doi.org/10.1007/s12613-022-2501-9
Abstract:
The metallurgy industry consumes a considerable amount of coal and fossil fuels, and its carbon dioxide emissions are increasing every year. Replacing coal with renewable, carbon-neutral biomass for metallurgical production is of great significance in reducing global carbon consumption. This study describes the current state of research in biomass metallurgy in recent years and analyzes the concept and scientific principles of biomass metallurgy. The fundamentals of biomass pretreatment technology and biomass metallurgy technology were discussed, and the industrial application framework of biomass metallurgy was proposed. Furthermore, the economic and social advantages of biomass metallurgy were analyzed to serve as a reference for the advancement of fundamental theory and industrial application of biomass metallurgy.
The metallurgy industry consumes a considerable amount of coal and fossil fuels, and its carbon dioxide emissions are increasing every year. Replacing coal with renewable, carbon-neutral biomass for metallurgical production is of great significance in reducing global carbon consumption. This study describes the current state of research in biomass metallurgy in recent years and analyzes the concept and scientific principles of biomass metallurgy. The fundamentals of biomass pretreatment technology and biomass metallurgy technology were discussed, and the industrial application framework of biomass metallurgy was proposed. Furthermore, the economic and social advantages of biomass metallurgy were analyzed to serve as a reference for the advancement of fundamental theory and industrial application of biomass metallurgy.
2022, vol. 29, no. 6, pp.
1150-1160.
https://doi.org/10.1007/s12613-021-2379-y
Abstract:
Although azurite is one of the most important copper oxide minerals, the recovery of this mineral via sulfidization–xanthate flotation is typically unsatisfactory. The present work demonstrated the enhanced sulfidization of azurite surfaces using ammonia phosphate ((NH4)3PO4) together with Na2S, based on micro-flotation experiments, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, contact angle measurements, Fourier-transform infrared (FT-IR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. Micro-flotation experiments showed that the floatability of azurite was increased following the simultaneous addition of (NH4)3PO4 and Na2S. ToF-SIMS and XPS analyses demonstrated the formation of a high content of S species on the azurite surface and an increase in the number of Cu(I) species after exposure to (NH4)3PO4 and Na2S, compared with the azurite–Na2S system. The zeta potential of azurite particles was negatively shifted and the contact angle on the azurite surface was increased with the addition of (NH4)3PO4 prior to Na2S. These results indicate that treatment with (NH4)3PO4 enhances the sulfidization of azurite surfaces, which in turn promotes xanthate attachment. FT-IR and UV–Vis analyses confirmed that the addition of (NH4)3PO4 increased the adsorption of xanthate with reducing the consumption of xanthate during the azurite flotation process. Thus, (NH4)3PO4 has a beneficial effect on the sulfidization flotation of azurite.
Although azurite is one of the most important copper oxide minerals, the recovery of this mineral via sulfidization–xanthate flotation is typically unsatisfactory. The present work demonstrated the enhanced sulfidization of azurite surfaces using ammonia phosphate ((NH4)3PO4) together with Na2S, based on micro-flotation experiments, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, contact angle measurements, Fourier-transform infrared (FT-IR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. Micro-flotation experiments showed that the floatability of azurite was increased following the simultaneous addition of (NH4)3PO4 and Na2S. ToF-SIMS and XPS analyses demonstrated the formation of a high content of S species on the azurite surface and an increase in the number of Cu(I) species after exposure to (NH4)3PO4 and Na2S, compared with the azurite–Na2S system. The zeta potential of azurite particles was negatively shifted and the contact angle on the azurite surface was increased with the addition of (NH4)3PO4 prior to Na2S. These results indicate that treatment with (NH4)3PO4 enhances the sulfidization of azurite surfaces, which in turn promotes xanthate attachment. FT-IR and UV–Vis analyses confirmed that the addition of (NH4)3PO4 increased the adsorption of xanthate with reducing the consumption of xanthate during the azurite flotation process. Thus, (NH4)3PO4 has a beneficial effect on the sulfidization flotation of azurite.
2022, vol. 29, no. 6, pp.
1161-1169.
https://doi.org/10.1007/s12613-020-2148-3
Abstract:
The effect of calcination temperature on the pozzolanic activity of maize straw stem ash (MSSA) was evaluated. The MSSA samples calcined at temperature values of 500, 700, and 850°C were dissolved in portlandite solution for 6 h, thereby obtaining residual samples. The MSSA and MSSA residual samples were analyzed using Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy to determine vibration bonds, minerals, microstructures, and Si 2p transformation behavior. The conductivity, pH value, and loss of conductivity with dissolving time of the MSSA-portlandite mixed solution were also determined. The main oxide composition of MSSA was silica and potassium oxide. The dissolution of the Si4+ content of MSSA at 500°C was higher than those of the other calcination temperatures. The conductivity and loss of conductivity of MSSA at 700°C were higher than those of the other calcination temperatures at a particular dissolving time due to the higher KCl content in MSSA at 700°C. C–S–H was easily identified in MSSA samples using X-ray powder diffraction, and small cubic and nearly spherical particles of C–S–H were found in the MSSA residual samples. In conclusion, the optimum calcination temperature of MSSA having the best pozzolanic activity is 500°C, but excessive agglomeration must be prevented.
The effect of calcination temperature on the pozzolanic activity of maize straw stem ash (MSSA) was evaluated. The MSSA samples calcined at temperature values of 500, 700, and 850°C were dissolved in portlandite solution for 6 h, thereby obtaining residual samples. The MSSA and MSSA residual samples were analyzed using Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy to determine vibration bonds, minerals, microstructures, and Si 2p transformation behavior. The conductivity, pH value, and loss of conductivity with dissolving time of the MSSA-portlandite mixed solution were also determined. The main oxide composition of MSSA was silica and potassium oxide. The dissolution of the Si4+ content of MSSA at 500°C was higher than those of the other calcination temperatures. The conductivity and loss of conductivity of MSSA at 700°C were higher than those of the other calcination temperatures at a particular dissolving time due to the higher KCl content in MSSA at 700°C. C–S–H was easily identified in MSSA samples using X-ray powder diffraction, and small cubic and nearly spherical particles of C–S–H were found in the MSSA residual samples. In conclusion, the optimum calcination temperature of MSSA having the best pozzolanic activity is 500°C, but excessive agglomeration must be prevented.
2022, vol. 29, no. 6, pp.
1170-1178.
https://doi.org/10.1007/s12613-021-2262-x
Abstract:
Aiming at the process of smelting ultra-high (>80%) or even full vanadium titanomagnetite in blast furnace, we are conducting a series of works on physics character of high TiO2 bearing blast furnace slag (BFS) for slag optimization. This work discussed the density and surface tension of high TiO2 bearing BFS using the Archimedean principle and the maximum bubble pressure method, respectively. The influence of TiO2 content and the MgO/CaO mass ratio on the density and surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags were investigated. Results indicated that the density of slags decreased with the TiO2 content increasing from 20wt% to 30wt%, but it increased slightly with the MgO/CaO mass ratio increasing from 0.32 to 0.73. In view of silicate network structure, the density and the degree of polymerization (DOP) of network structure have a consistent trend. The addition of TiO2 reduced (Q3)2/(Q2) ratio (Q2 and Q3 represent structural unit with bridge oxygen number of 2 and 3, respectively) and then decreased DOP, which led to the decrease of slag density. The surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags decreased dramatically with the TiO2 content increasing from 20wt% to 30wt%. Conversely, it increased with the MgO/CaO mass ratio increasing from 0.32 to 0.73. Furthermore, the iso-surface tension lines were obtained under 1723 K using the Tanaka developed model in view of Butler formula. It may be useful for slag optimization of ultra-high proportion (>80%) or even full vanadium titanomagnetite under BF smelting.
Aiming at the process of smelting ultra-high (>80%) or even full vanadium titanomagnetite in blast furnace, we are conducting a series of works on physics character of high TiO2 bearing blast furnace slag (BFS) for slag optimization. This work discussed the density and surface tension of high TiO2 bearing BFS using the Archimedean principle and the maximum bubble pressure method, respectively. The influence of TiO2 content and the MgO/CaO mass ratio on the density and surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags were investigated. Results indicated that the density of slags decreased with the TiO2 content increasing from 20wt% to 30wt%, but it increased slightly with the MgO/CaO mass ratio increasing from 0.32 to 0.73. In view of silicate network structure, the density and the degree of polymerization (DOP) of network structure have a consistent trend. The addition of TiO2 reduced (Q3)2/(Q2) ratio (Q2 and Q3 represent structural unit with bridge oxygen number of 2 and 3, respectively) and then decreased DOP, which led to the decrease of slag density. The surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags decreased dramatically with the TiO2 content increasing from 20wt% to 30wt%. Conversely, it increased with the MgO/CaO mass ratio increasing from 0.32 to 0.73. Furthermore, the iso-surface tension lines were obtained under 1723 K using the Tanaka developed model in view of Butler formula. It may be useful for slag optimization of ultra-high proportion (>80%) or even full vanadium titanomagnetite under BF smelting.
2022, vol. 29, no. 6, pp.
1179-1185.
https://doi.org/10.1007/s12613-021-2300-8
Abstract:
The interfacial phenomena in mold have a great impact on the smooth operation of continuous casting process and the quality of the casting product. In this paper, the wetting behavior of CaO–Al2O3-based mold flux with different BaO and MgO contents was studied. The results showed that the contact angle between molten flux and interstitial free (IF) steel substrate increased from 62.4° to 74.5° with the increase of BaO content from 3wt% to 7wt%, while it decreased from 62.4° to 51.3° with the increase of MgO content from 3wt% to 7wt%. The interfacial tension also increased from 1630.3 to 1740.8 mN/m when the BaO content increased, but it reduced from 1630.3 to 1539.7 mN/m with the addition of MgO. The changes of contact angle and interfacial tension were mainly due to the fact that the bridging oxygen (O0) at the interface was broken into non-bridging oxygen (O−) and free oxygen (O2−) by MgO. However, more O− and O2− connected into O0 when BaO was added, since the charge compensation effect of BaO was so stronger that it offset the effect of providing O2−.
The interfacial phenomena in mold have a great impact on the smooth operation of continuous casting process and the quality of the casting product. In this paper, the wetting behavior of CaO–Al2O3-based mold flux with different BaO and MgO contents was studied. The results showed that the contact angle between molten flux and interstitial free (IF) steel substrate increased from 62.4° to 74.5° with the increase of BaO content from 3wt% to 7wt%, while it decreased from 62.4° to 51.3° with the increase of MgO content from 3wt% to 7wt%. The interfacial tension also increased from 1630.3 to 1740.8 mN/m when the BaO content increased, but it reduced from 1630.3 to 1539.7 mN/m with the addition of MgO. The changes of contact angle and interfacial tension were mainly due to the fact that the bridging oxygen (O0) at the interface was broken into non-bridging oxygen (O−) and free oxygen (O2−) by MgO. However, more O− and O2− connected into O0 when BaO was added, since the charge compensation effect of BaO was so stronger that it offset the effect of providing O2−.
2022, vol. 29, no. 6, pp.
1186-1196.
https://doi.org/10.1007/s12613-020-2192-z
Abstract:
21Cr2NiMo steel is widely used to stabilize offshore oil platforms; however, it suffers from stress-corrosion cracking (SCC). Herein, we studied the SCC behavior of 21Cr2NiMo steel in SO2-polluted coastal atmospheres. Electrochemical tests revealed that the addition of SO2 increased the corrosion current. Rust characterization showed that SO2 addition densified the corrosion products and promoted pitting. Furthermore, slow strain rate tests demonstrated a high susceptibility to SCC in high SO2 contents. Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes. In conclusion, SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.
21Cr2NiMo steel is widely used to stabilize offshore oil platforms; however, it suffers from stress-corrosion cracking (SCC). Herein, we studied the SCC behavior of 21Cr2NiMo steel in SO2-polluted coastal atmospheres. Electrochemical tests revealed that the addition of SO2 increased the corrosion current. Rust characterization showed that SO2 addition densified the corrosion products and promoted pitting. Furthermore, slow strain rate tests demonstrated a high susceptibility to SCC in high SO2 contents. Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes. In conclusion, SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.
2022, vol. 29, no. 6, pp.
1197-1205.
https://doi.org/10.1007/s12613-022-2479-3
Abstract:
It is difficult to rapidly design the process parameters of copper alloys by using the traditional trial-and-error method and simultaneously improve the conflicting mechanical and electrical properties. The purpose of this work is to develop a new type of Cu–Ni–Co–Si alloy saving scarce and expensive Co element, in which the Co content is less than half of the lower limit in ASTM standard C70350 alloy, while the properties are as the same level as C70350 alloy. Here we adopted a strategy combining Bayesian optimization machine learning and experimental iteration and quickly designed the secondary deformation-aging parameters (cold rolling deformation 90%, aging temperature 450°C, and aging time 1.25 h) of the new copper alloy with only 32 experiments (27 basic sample data acquisition experiments and 5 iteration experiments), which broke through the barrier of low efficiency and high cost of trial-and-error design of deformation-aging parameters in precipitation strengthened copper alloy. The experimental hardness, tensile strength, and electrical conductivity of the new copper alloy are HV (285 ± 4), (872 ± 3) MPa, and (44.2 ± 0.7)% IACS (international annealed copper standard), reaching the property level of the commercial lead frame C70350 alloy. This work provides a new idea for the rapid design of material process parameters and the simultaneous improvement of mechanical and electrical properties.
It is difficult to rapidly design the process parameters of copper alloys by using the traditional trial-and-error method and simultaneously improve the conflicting mechanical and electrical properties. The purpose of this work is to develop a new type of Cu–Ni–Co–Si alloy saving scarce and expensive Co element, in which the Co content is less than half of the lower limit in ASTM standard C70350 alloy, while the properties are as the same level as C70350 alloy. Here we adopted a strategy combining Bayesian optimization machine learning and experimental iteration and quickly designed the secondary deformation-aging parameters (cold rolling deformation 90%, aging temperature 450°C, and aging time 1.25 h) of the new copper alloy with only 32 experiments (27 basic sample data acquisition experiments and 5 iteration experiments), which broke through the barrier of low efficiency and high cost of trial-and-error design of deformation-aging parameters in precipitation strengthened copper alloy. The experimental hardness, tensile strength, and electrical conductivity of the new copper alloy are HV (285 ± 4), (872 ± 3) MPa, and (44.2 ± 0.7)% IACS (international annealed copper standard), reaching the property level of the commercial lead frame C70350 alloy. This work provides a new idea for the rapid design of material process parameters and the simultaneous improvement of mechanical and electrical properties.
2022, vol. 29, no. 6, pp.
1206-1215.
https://doi.org/10.1007/s12613-020-2209-7
Abstract:
This study investigated the microstructure, physical, and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification. Different frequencies (0, 20, 30, 40, and 50 Hz) at constant amplitude (31 μm) were employed using a power amplifier as the power input device. X-ray diffraction, optical microscopy, and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions. Metallurgical features of the castings were evaluated using ImageJ software. The average values of metallurgical features, including primary α-Al grain size, dendrite arm spacing, average area of eutectic silicon, aspect ratio, and percentage porosity, reduced by 34%, 59%, 56%, 22%, and 62%, respectively, at 30 Hz frequency compared with stationary casting. Mechanical tests of the cast samples showed that the yield strength (YS), ultimate tensile strength (UTS), percentage elongation (%EL), and microhardness (HV) increased by 8%, 13%, 17%, and 16%, respectively, at 30 Hz frequency compared with stationary casting. The fractured surface of the tensile specimens exhibited mixed-mode fracture behavior because of brittle facets, cleavage facets, ductile tearing, and dimple morphologies. The presence of small dimples showed that plastic deformation occurred before fracture.
This study investigated the microstructure, physical, and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification. Different frequencies (0, 20, 30, 40, and 50 Hz) at constant amplitude (31 μm) were employed using a power amplifier as the power input device. X-ray diffraction, optical microscopy, and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions. Metallurgical features of the castings were evaluated using ImageJ software. The average values of metallurgical features, including primary α-Al grain size, dendrite arm spacing, average area of eutectic silicon, aspect ratio, and percentage porosity, reduced by 34%, 59%, 56%, 22%, and 62%, respectively, at 30 Hz frequency compared with stationary casting. Mechanical tests of the cast samples showed that the yield strength (YS), ultimate tensile strength (UTS), percentage elongation (%EL), and microhardness (HV) increased by 8%, 13%, 17%, and 16%, respectively, at 30 Hz frequency compared with stationary casting. The fractured surface of the tensile specimens exhibited mixed-mode fracture behavior because of brittle facets, cleavage facets, ductile tearing, and dimple morphologies. The presence of small dimples showed that plastic deformation occurred before fracture.
2022, vol. 29, no. 6, pp.
1216-1224.
https://doi.org/10.1007/s12613-020-2222-x
Abstract:
The friction pull plug welding (FPPW) of the 2219-T87 tungsten inert gas (TIG) welded joint was investigated, and the microstructures, precipitate evolution, mechanical properties, and fracture morphologies of this joint were analyzed and discussed. In this study, defect-free joints were obtained using a rotational speed of 7000 r/min, an axial feeding displacement of 12 mm, and an axial force of 20–22 kN. The results indicated that within these welding parameters, metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains. The microstructural features of the FPPW joint can be divided into different regions, including the heat-affected zone (HAZ), thermomechanically affected zone (TMAZ), recrystallization zone (RZ), heat-affected zone in the TIG weld (TIG-HAZ), and the thermomechanically affected zone in the TIG weld (TIG-TMAZ). In the TIG-TMAZ, the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process. The main reason for the softening in the TMAZ is determined to be the dissolution of θ' and coarsening of θ precipitate particles. In a tensile test, the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa. The locations of cracks and factures in the TIG-TMAZ were identified. The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.
The friction pull plug welding (FPPW) of the 2219-T87 tungsten inert gas (TIG) welded joint was investigated, and the microstructures, precipitate evolution, mechanical properties, and fracture morphologies of this joint were analyzed and discussed. In this study, defect-free joints were obtained using a rotational speed of 7000 r/min, an axial feeding displacement of 12 mm, and an axial force of 20–22 kN. The results indicated that within these welding parameters, metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains. The microstructural features of the FPPW joint can be divided into different regions, including the heat-affected zone (HAZ), thermomechanically affected zone (TMAZ), recrystallization zone (RZ), heat-affected zone in the TIG weld (TIG-HAZ), and the thermomechanically affected zone in the TIG weld (TIG-TMAZ). In the TIG-TMAZ, the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process. The main reason for the softening in the TMAZ is determined to be the dissolution of θ' and coarsening of θ precipitate particles. In a tensile test, the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa. The locations of cracks and factures in the TIG-TMAZ were identified. The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.
2022, vol. 29, no. 6, pp.
1225-1230.
https://doi.org/10.1007/s12613-021-2252-z
Abstract:
This study aims to investigate the effects of heat treatments on the microstructure of γ-TiAl alloys. Two Ti–47Al–2Cr–2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat treatments. Their microstructures were studied by both optical and scanning electron microscopies. The chemical compositions of two ingots were determined as well. The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within 1270 to 1185°C. A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures. They are distributed at grain boundaries when holding at a higher temperature, such as 1260°C. However, B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185°C. Furthermore, the effects of heat treatments on grain refinement and other microstructural parameters are discussed.
This study aims to investigate the effects of heat treatments on the microstructure of γ-TiAl alloys. Two Ti–47Al–2Cr–2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat treatments. Their microstructures were studied by both optical and scanning electron microscopies. The chemical compositions of two ingots were determined as well. The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within 1270 to 1185°C. A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures. They are distributed at grain boundaries when holding at a higher temperature, such as 1260°C. However, B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185°C. Furthermore, the effects of heat treatments on grain refinement and other microstructural parameters are discussed.
2022, vol. 29, no. 6, pp.
1231-1236.
https://doi.org/10.1007/s12613-020-2214-x
Abstract:
New refractory high-entropy alloys, CrHfNbTaTi and CrHfMoTaTi, derived from the well-known HfNbTaTiZr alloy through principal element substitution were prepared using vacuum arc melting. The phase components, microstructures, and compressive properties of the alloys in the as-cast state were investigated. Results showed that both alloys were composed of BCC and cubic Laves phases. In terms of mechanical properties, the yield strength increased remarkably from 926 MPa for HfNbTaTiZr to 1258 MPa for CrHfNbTaTi, whereas a promising plastic strain of around 15.0% was retained in CrHfNbTaTi. The morphology and composition of the network-shaped interdendritic regions were closely related to the improved mechanical properties due to elemental substitution. Dendrites were surrounded by an incompact interdendritic shell after Mo incorporation, which deteriorated yield strength and accelerated brittleness.
New refractory high-entropy alloys, CrHfNbTaTi and CrHfMoTaTi, derived from the well-known HfNbTaTiZr alloy through principal element substitution were prepared using vacuum arc melting. The phase components, microstructures, and compressive properties of the alloys in the as-cast state were investigated. Results showed that both alloys were composed of BCC and cubic Laves phases. In terms of mechanical properties, the yield strength increased remarkably from 926 MPa for HfNbTaTiZr to 1258 MPa for CrHfNbTaTi, whereas a promising plastic strain of around 15.0% was retained in CrHfNbTaTi. The morphology and composition of the network-shaped interdendritic regions were closely related to the improved mechanical properties due to elemental substitution. Dendrites were surrounded by an incompact interdendritic shell after Mo incorporation, which deteriorated yield strength and accelerated brittleness.
2022, vol. 29, no. 6, pp.
1237-1248.
https://doi.org/10.1007/s12613-020-2240-8
Abstract:
Interfacial bonding, microstructures, and mechanical properties of an explosively-welded H68/AZ31B clad plate were systematically studied. According to the results, the bonding interface demonstrated a “wavy-like” structure containing three typical zones/layers: (1) diffusion layer adjacent to the H68 brass plate; (2) solidification layer of melted metals at the interface; (3) a layer at the side of AZ31B alloy that experienced severe deformation. Mixed copper, CuZn2, and α-Mg phases were observed in the melted-solidification layer. Regular polygonal grains with twins were found at the H68 alloy side, while fine equiaxed grains were found at the AZ31B alloy side near the interface due to recrystallization. Nanoindentation results revealed the formation of brittle intermetallic CuZn2 phases at the bonding interface. The interface was bonded well through metallurgical reactions due to diffusion of Cu, Zn, and Mg atoms across the interface and metallurgic reaction of partially melted H68 and AZ31B alloys.
Interfacial bonding, microstructures, and mechanical properties of an explosively-welded H68/AZ31B clad plate were systematically studied. According to the results, the bonding interface demonstrated a “wavy-like” structure containing three typical zones/layers: (1) diffusion layer adjacent to the H68 brass plate; (2) solidification layer of melted metals at the interface; (3) a layer at the side of AZ31B alloy that experienced severe deformation. Mixed copper, CuZn2, and α-Mg phases were observed in the melted-solidification layer. Regular polygonal grains with twins were found at the H68 alloy side, while fine equiaxed grains were found at the AZ31B alloy side near the interface due to recrystallization. Nanoindentation results revealed the formation of brittle intermetallic CuZn2 phases at the bonding interface. The interface was bonded well through metallurgical reactions due to diffusion of Cu, Zn, and Mg atoms across the interface and metallurgic reaction of partially melted H68 and AZ31B alloys.
Mechanical properties of Al–15Mg2Si composites prepared under different solidification cooling rates
2022, vol. 29, no. 6, pp.
1249-1260.
https://doi.org/10.1007/s12613-020-2244-4
Abstract:
The effect of different cooling rates (2.7, 5.5, 17.1, and 57.5°C/s) on the solidification parameters, microstructure, and mechanical properties of Al−15Mg2Si composites was studied. The results showed that a high cooling rate refined the Mg2Si particles and changed their morphology to more compacted forms with less microcracking tendency. The average radius and fraction of primary Mg2Si particles decreased from 20 µm and 13.5% to about 10 µm and 7.3%, respectively, as the cooling rate increased from 2.7 to 57.5°C/s. Increasing the cooling rate also improved the distribution of microconstituents and decreased the grain size and volume fraction of micropores. The mechanical properties results revealed that augmenting the cooling rate from 2.7 to about 57.5°C/s increased the hardness and quality index by 25% and 245%, respectively. The high cooling rate also changed the fracture mechanism from a brittle-dominated mode to a high-energy ductile mode comprising extensive dimpled zones.
The effect of different cooling rates (2.7, 5.5, 17.1, and 57.5°C/s) on the solidification parameters, microstructure, and mechanical properties of Al−15Mg2Si composites was studied. The results showed that a high cooling rate refined the Mg2Si particles and changed their morphology to more compacted forms with less microcracking tendency. The average radius and fraction of primary Mg2Si particles decreased from 20 µm and 13.5% to about 10 µm and 7.3%, respectively, as the cooling rate increased from 2.7 to 57.5°C/s. Increasing the cooling rate also improved the distribution of microconstituents and decreased the grain size and volume fraction of micropores. The mechanical properties results revealed that augmenting the cooling rate from 2.7 to about 57.5°C/s increased the hardness and quality index by 25% and 245%, respectively. The high cooling rate also changed the fracture mechanism from a brittle-dominated mode to a high-energy ductile mode comprising extensive dimpled zones.
2022, vol. 29, no. 6, pp.
1261-1269.
https://doi.org/10.1007/s12613-020-2243-5
Abstract:
The fabrication of boron carbide reinforced aluminum matrix composites (Al‒B4C) with various contents of B4C (1wt%, 6wt%, 15wt%, and 30wt%) was performed by powder metallurgy, and the influence of the content of B4C on their mechanical and tribological behavior was examined. The Al‒30B4C composites recorded the highest density (~2.54 g/cm3), lowest porosity (4%), maximum Vickers hardness (HV ~75), lowest weight loss (0.4 mg), and lowest specific wear rate (0.00042 mm3/(N·m)) under a load of 7 N, with an enhancement of 167% in hardness, a decrease of 75.8% in weight loss, and a decrease of 76.7% in the specific wear rate compared with pure aluminum. In addition, the scanning electron microscope images of the worn surface revealed that the Al‒B4C composite has the narrowest wear groove of 0.85 mm at a load of 7 N, and the main wear mechanism was observed as an abrasive wear mechanism. According to the friction analysis, the coefficient of friction between surfaces increased with increasing boron carbide content and with decreasing applied load. In conclusion, B4C is an effective reinforcement material in terms of tribological and mechanical performance of the Al‒B4C composites.
The fabrication of boron carbide reinforced aluminum matrix composites (Al‒B4C) with various contents of B4C (1wt%, 6wt%, 15wt%, and 30wt%) was performed by powder metallurgy, and the influence of the content of B4C on their mechanical and tribological behavior was examined. The Al‒30B4C composites recorded the highest density (~2.54 g/cm3), lowest porosity (4%), maximum Vickers hardness (HV ~75), lowest weight loss (0.4 mg), and lowest specific wear rate (0.00042 mm3/(N·m)) under a load of 7 N, with an enhancement of 167% in hardness, a decrease of 75.8% in weight loss, and a decrease of 76.7% in the specific wear rate compared with pure aluminum. In addition, the scanning electron microscope images of the worn surface revealed that the Al‒B4C composite has the narrowest wear groove of 0.85 mm at a load of 7 N, and the main wear mechanism was observed as an abrasive wear mechanism. According to the friction analysis, the coefficient of friction between surfaces increased with increasing boron carbide content and with decreasing applied load. In conclusion, B4C is an effective reinforcement material in terms of tribological and mechanical performance of the Al‒B4C composites.
2022, vol. 29, no. 6, pp.
1270-1279.
https://doi.org/10.1007/s12613-020-2217-7
Abstract:
A Zn–38Al–3.5Cu–1.2Mg composite reinforced with nano-SiCp was fabricated via stirring-assisted ultrasonic vibration. To improve the abrasive resistance of the Zn–38Al–3.5Cu–1.2Mg/SiCp composite, several stabilization treatments with distinct solid solutions and aging temperatures were designed. The results indicated that the optimal stabilization treatment for the Zn–38Al–3.5Cu–1.2Mg/SiCp composite comprised solution treatment at 380°C for 6 h and aging at 170°C for 48 h. The stabilization treatment led to the formation of dispersive and homogeneous nano-SiCp. During the friction wear condition, the nano-SiCp limited the microstructure evolution from the hard α(Al,Zn) phase to the soft β(Al,Zn) phase. Moreover, the increased amount of nano-SiCp improved the grain dimension and contributed to the composite abrasive resistance. Furthermore, the stabilization treatment suppressed the crack initiation and propagation in the friction wear process, thereby improving the abrasive resistance of the Zn–38Al–3.5Cu–1.2Mg/SiCp composite.
A Zn–38Al–3.5Cu–1.2Mg composite reinforced with nano-SiCp was fabricated via stirring-assisted ultrasonic vibration. To improve the abrasive resistance of the Zn–38Al–3.5Cu–1.2Mg/SiCp composite, several stabilization treatments with distinct solid solutions and aging temperatures were designed. The results indicated that the optimal stabilization treatment for the Zn–38Al–3.5Cu–1.2Mg/SiCp composite comprised solution treatment at 380°C for 6 h and aging at 170°C for 48 h. The stabilization treatment led to the formation of dispersive and homogeneous nano-SiCp. During the friction wear condition, the nano-SiCp limited the microstructure evolution from the hard α(Al,Zn) phase to the soft β(Al,Zn) phase. Moreover, the increased amount of nano-SiCp improved the grain dimension and contributed to the composite abrasive resistance. Furthermore, the stabilization treatment suppressed the crack initiation and propagation in the friction wear process, thereby improving the abrasive resistance of the Zn–38Al–3.5Cu–1.2Mg/SiCp composite.
2022, vol. 29, no. 6, pp.
1280-1285.
https://doi.org/10.1007/s12613-021-2361-8
Abstract:
The self-assembly process for compatible functional layers of devices is a simple, feasible, and energy-saving strategy. In mesoporous perovskite solar cells (PSCs), compact and scaffold TiO2 films generally function as the hole-blocking and electron-transporting layers, respectively. However, both of these layers are usually generated through a high-temperature annealing process. Here, we deposited TiO2 compact films through a room-temperature self-assembly process as effective hole-blocking layers for PSCs. The thickness of TiO2 compact films can be easily controlled by the deposition time. Through the optimization of TiO2 compact films (80 nm), the power conversion efficiency (PCE) of mesoporous PSCs without and with hole conductor layers increases up to 10.66% and 17.95%, respectively. Notably, an all-low-temperature planar PSC with the self-assembled TiO2 layer exhibits a PCE of 16.41%.
The self-assembly process for compatible functional layers of devices is a simple, feasible, and energy-saving strategy. In mesoporous perovskite solar cells (PSCs), compact and scaffold TiO2 films generally function as the hole-blocking and electron-transporting layers, respectively. However, both of these layers are usually generated through a high-temperature annealing process. Here, we deposited TiO2 compact films through a room-temperature self-assembly process as effective hole-blocking layers for PSCs. The thickness of TiO2 compact films can be easily controlled by the deposition time. Through the optimization of TiO2 compact films (80 nm), the power conversion efficiency (PCE) of mesoporous PSCs without and with hole conductor layers increases up to 10.66% and 17.95%, respectively. Notably, an all-low-temperature planar PSC with the self-assembled TiO2 layer exhibits a PCE of 16.41%.
2022, vol. 29, no. 6, pp.
1286-1294.
https://doi.org/10.1007/s12613-021-2363-6
Abstract:
Cr3+-activated far-red and near-infrared phosphors have drawn considerable attention owing to their adjustable emission wavelengths and wide applications. Herein, we reported a series of Cr3+-doped phosphors with β-Ca3(PO4)2-type structure, of which Ca9Ga(PO4)7:Cr3+ possessed the highest far-red emission intensity. At an excitation of 440 nm, the Ca9Ga(PO4)7:Cr3+ phosphors exhibited a broad emission band ranging from 650 to 850 nm and peaking at 735 nm, and the broadband superimposed two sharp lines centering at 690 and 698 nm. The optimal sample Ca9Ga0.97(PO4)7:0.03Cr3+ had an internal quantum efficiency of 55.7%. The luminescence intensity of the Ca9Ga0.97(PO4)7:0.03Cr3+ phosphor obtained at 423 K could maintain 68.5% of that at room temperature, demonstrating its outstanding luminescence thermal stability. A phosphor-conversion light-emitting diode was fabricated, indicating that the Ca9Ga(PO4)7:Cr3+ phosphor has potential applications in indoor plant cultivation.
Cr3+-activated far-red and near-infrared phosphors have drawn considerable attention owing to their adjustable emission wavelengths and wide applications. Herein, we reported a series of Cr3+-doped phosphors with β-Ca3(PO4)2-type structure, of which Ca9Ga(PO4)7:Cr3+ possessed the highest far-red emission intensity. At an excitation of 440 nm, the Ca9Ga(PO4)7:Cr3+ phosphors exhibited a broad emission band ranging from 650 to 850 nm and peaking at 735 nm, and the broadband superimposed two sharp lines centering at 690 and 698 nm. The optimal sample Ca9Ga0.97(PO4)7:0.03Cr3+ had an internal quantum efficiency of 55.7%. The luminescence intensity of the Ca9Ga0.97(PO4)7:0.03Cr3+ phosphor obtained at 423 K could maintain 68.5% of that at room temperature, demonstrating its outstanding luminescence thermal stability. A phosphor-conversion light-emitting diode was fabricated, indicating that the Ca9Ga(PO4)7:Cr3+ phosphor has potential applications in indoor plant cultivation.
2022, vol. 29, no. 6, pp.
1295-1303.
https://doi.org/10.1007/s12613-020-2215-9
Abstract:
ZnSnO3 nanocubes (ZSNCs) with various Pt concentrations (i.e., 1at%, 2at%, and 5at%) were synthesized by a simple one-pot hydrothermal method. The microstructures of pure and Pt-doped ZSNCs were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results showed that the pure ZSNCs have a perovskite structure with a side length of approximately 600 nm; this length was reduced to 400 nm after Pt doping. Following doping, PtOx (PtO and PtO2) nanoparticles with a diameter of approximately 5 nm were uniformly coated on the surface of the ZSNCs. Systematic investigation of the gas-sensing abilities of the nanocubes showed that the Pt-doped ZSNCs have excellent sensing properties toward nitrogen dioxide (NO2) gas in the operating temperature range of 75–175°C. Among the sensors prepared, that based on 1at% Pt-doped ZSNCs exhibited the best response of 16.0 toward 500 ppb NO2 at 125°C; this response is over 11 times higher compared with that of pure ZSNCs. The enhanced NO2 sensing mechanism of the Pt-doped ZSNCs may be attributed to the synergistic effects of catalytic activity and chemical sensitization by Pt doping.
ZnSnO3 nanocubes (ZSNCs) with various Pt concentrations (i.e., 1at%, 2at%, and 5at%) were synthesized by a simple one-pot hydrothermal method. The microstructures of pure and Pt-doped ZSNCs were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results showed that the pure ZSNCs have a perovskite structure with a side length of approximately 600 nm; this length was reduced to 400 nm after Pt doping. Following doping, PtOx (PtO and PtO2) nanoparticles with a diameter of approximately 5 nm were uniformly coated on the surface of the ZSNCs. Systematic investigation of the gas-sensing abilities of the nanocubes showed that the Pt-doped ZSNCs have excellent sensing properties toward nitrogen dioxide (NO2) gas in the operating temperature range of 75–175°C. Among the sensors prepared, that based on 1at% Pt-doped ZSNCs exhibited the best response of 16.0 toward 500 ppb NO2 at 125°C; this response is over 11 times higher compared with that of pure ZSNCs. The enhanced NO2 sensing mechanism of the Pt-doped ZSNCs may be attributed to the synergistic effects of catalytic activity and chemical sensitization by Pt doping.
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